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MY DOG IS BETTER THAN YOURS: AN EXAMINATION OF THE PAIN ATTENUATING PROPERTIES ASSOCIATED WITH EXPOSURE TO A FAMILIAR DOG, AN UNFAMILIAR DOG, AND A PLANT BY EMMA JANE BALLANTINE A Thesis Submitted to the Division of Social Science s New College of Florida in partial fulfillment of the requirements for the degree Bachelor of Arts Under the sponsorship of Michelle E. Barton Sarasota, Florida May, 2012
ii Acknowledgements I would like to extend my gratitude and to all of the amaz ing individuals who lent their support, both emotional and academic. There are a handful of academic mentors that I must acknowledge due to their important contribution to my thesis. First and foremost, I would like to thank my academic advisor and thesis sponsor, Dr. Michelle Barton, for her guidance and support over the past year. You have been a great source of motivation and inspiration to me not only during the thesis process but also during my entire New College career. I would like to extend a heart felt thank you to my committee members, Dr. Heidy Harley, and Dr. Maribeth Clark. This year has been crazy for all of us, and I sincerely appreciate the contribution of your time. Dr. Duff Cooper gladly provided many hours of much needed and appreciated h elp in analyzing my data. Without your patience and dedication I'm sure that I would still be grappling with the seemingly endless statistical tests. Finally, I would like to thank all of the individuals who helped facilitate my vision. Jennie Caskey, my research assistant, took time out of her busy schedule to help me with data collection. You are my very own dog whisperer, and your photography skills were invaluable. I send a long deep scratch behind the ears to my dog, Tucker for inspiring my research q uestion, and always being there to quell the pain. I would like to extend my deepest gratitude to all of my lovely participants (human and canine), who helped make this experiment possible.
iii Table Of Contents ACKNOWLEDGMENTS.......ii TABLE OF CONTENTS.......iii LIST OF TABLES......iv ABSTRACT.v INTRODUCTION...1 Physiological and Psychological Benefits Associated with Short Term Ex posure to Companion Animals....................................6 Benefits Associated with Long Term Exposure to Companion Animals..11 Social Support and Attachment.....15 Biophilia.....23 Pain Re duction Associated with Exposure to Companion Animals vs. Human Social Support....26 The Current Study..36 METHOD......38 RESULTS..43 DISCUSSION ....50 REFERENCES..60 APPENDIX A79 APPENDIX B80 APPENDIX C85 APPENDIX D........86
iv List of Fig ures FIGURE 1......70 FIGURE 2..71 FIGURE 3..72 FIGURE4...73 FIGURE 5..74 FIGURE 6 ..75 FIGURE 7..76 FIGURE 8..77 FIGURE 9..78
v MY DOG IS BETTER THA N YOURS: AN EXAMINAT ION OF THE PAIN ATTENUATING PROPERTI ES ASSOCIATED WITH E XPOSURE TO A FAMILIA R DOG, AND UNFAMILIAR DOG, AND A PLANT Emma Ballantine New College of Florida, 2012 ABSTRACT Exposure to companion animals has been associated with reduced physiological reactivity, reduced pain and improved affect. Som e have suggested these effects may be due to the Biophilia hypothesis, which states that people receive a therapeutic benefit from exposure to nature, while others have argued that these effects are an effect of attachment. The current study compared the r eduction in pain experienced by participants during exposure to photographs of a familiar dog, an unfamiliar dog, a plant and a neutral stimulus (chair), through the use of a 3(Condition: familiar dog, unfamiliar dog, plant) x 2(Trial: chair, experimenta l) design, in an attempt to isolate the effects of attachment from the effects of Biophilia. The results revealed no differences between these groups on physiological responses including systolic blood pressure, diastolic blood pressure and heart rate. However there were significant differences in pain tolerance. Participants viewing the familiar dog had a higher pain tolerance than those viewing the unfamiliar dog or the chair. Additionally, participants viewing the plant had a higher pain tolerance tha n those viewing the chair. This suggests that a familiar dog may serve as a more effective pain intervention than an unfamiliar dog. Furthermore, the results suggest that
vi photographs of plants and familiar dogs are sufficient to foster pain reduction. _______________________ Dr. Michelle Barton Division of Psychology
1 My Dog is Better Than Yours: An Examination of the Pain Attenuating Properties Associated with Exposure to a Familiar Dog, and Unfamiliar Dog, and a Plant Animals have played a central ro le in the lives of humans as a source of food and resources for the past 2.6 billion years, and have lived intimately with humans for the last 40,000 (Shipman, 2010). Among the oldest of these intimate relationships is the one we share with companion speci es, specifically dogs. Man has cohabited with dogs for thousands of years. The remains of the earliest known domesticated dog, discovered in Gyoet Cave in Belgium, date back about 32,000 years (Shipman, 2010). To this day, owning a pet remains a widespread practice, particularly in the West. The 2009/2010 American National Pet Owners Survey found that 62% of all American households owned a pet, and 39% of these pet owners had at least one dog (American Pet Products Association (APPA); as cited by Zimolag, 2 011). These relationships do not appear to be just commonplace connections, but rather highly developed bonds between 2 different species. Indeed, there is a great deal of anecdotal evidence that suggests the bonds people share with companion animals are comparable to the bonds they share with other humans ( Castelli, Hart & Zasloff, 2001; Kurdek, 2009). The close connections humans feel towards non human animals is a universal construct that, while commonly observed in humans, is rarely observed in other m ammals (Shipman, 2010). This suggests that people might have evolved in response to the animals they domesticated. Herzog (2002) suggested that evolution guided humans towards a tendency to feel empathy for and be perceptive of the needs of nonhuman animal s,
2 implying that humans derive significant benefit from their relationships with companion species. Although people have lived closely with animals for several thousand years, only fairly recently have animals been introduced into a clinical setting. Anec dotal evidence on the benefits of interaction with animals long predates scientific research on the topic. In 1859, Florence Nightingale stated that, "A small pet animal is often an excellent companion for the sick or long chronic cases, especially" (p. 10 3). The experiences of a variety of individuals, including medical professionals like Nightingale, have added fuel to the notion that companion animals provide significant benefits to their owners. However, these statements were not supported by any scient ific research until 1961, when Dr. Boris Levinson documented his observations of his patients' interactions with companion animals (Levinson, 1984). Levinson's research on the benefits of companion animals has led to the emergence of animal assisted therap y, which sought to use these benefits to treat various social, emotional, motivational, or cognitive issues. Since his initial study, research into this field has grown substantially. Within such studies, numerous researchers have found that interactions with animals have beneficial effects on their owners (Ory & Goldberg, 1983; Fritz, Farver, Kass, & Hart, 1995; Jessen, Cardiello & Baun, 1996; Heady, 1999; Kidd & Kidd, 1999), as well as on people who are unfamiliar with the animal (Friedmann, 1983; DeMell o, 1999). Furthermore, physical health benefits associated with companion animals have been observed over many areas of human health, including, but not limited to, general wellness (Dembicki & Anderson, 1996; Raina, Waltner Toews, Bonnett, Woodward & Aber nathy, 1999; Enders Slegers, 2000), number of reported doctor visits (Siegel, 1990; Heady, 1999), survival rate
3 following heart complications (Friedmann & Thomas, 1998); improved physiological measures during periods of relaxation (Eddy, 1996) and during e xposure to stressors (Wilson & Netting, 1987; Vormbrock & Grossberg, 1988; Katcher, Beck & Levine, 1989). Two hypotheses have been developed to explain the mechanism behind the benefits observed during our interactions with companion animals. The Biophili a hypothesis was developed by E. O. Wilson in 1984, and was originally defined as the "Innate tendency to focus on life and life like processes" (Wilson, 1984, p. 1). Through this hypothesis, Wilson proposed that people possessed an affinity for what might be called the natural world, that they preferred it, and that they might derive benefit by being exposed to its elements. This includes benefits associated with exposure to natural landscapes ( Birget et al., 2008; Valtchanov, Barton, & Ellard, 2010 ), as w ell as animals ( Birget et al., 2008 ). This theory may serve to explain the reduction in blood pressure (Friedmann, 1983; DeMello, 1999 ) and pain ratings (Hansen, Messinger, Braun & Megel, 1999; Havener, Gentes, Thaler, Megel, Baun, Driscoll, & Agrawal, 200 1; Braun, 2009 ) associated with exposure to unfamiliar companion animals, thus providing one possible explanation for the therapeutic effects people experience during interactions with companion animals. Other researchers have suggested that the therapeut ic effects may be elicited via attachment bonds between humans and their companion animals (Beck, 2003; Wood, Giles Corti, & Bulsara, 2005). Studies of human attachment have found that people demonstrate reduced reactions to pain when they are exposed to a n attachment figure than when they are exposed to a stranger or a neutral stimulus (Master, Eisenberger, Taylor, Naliboff, Shirinyan, & Lieberman, 2009). McWilliams and Baily (2010) found that individuals with
4 high ratings on avoidant attachment were signi ficantly more likely to have conditions that involve pain symptoms, and those with high ratings on anxious attachment were more likely to have conditions that involve the cardiovascular system, such as high blood pressure, heart attack, and stroke. Resear ch has demonstrated that people are attached to their pets, much like they are attached to other people (Cohen, 2002; Chur Hansen, Winefield, & Beckwith, 2009). Furthermore, most people are securely attached to their pets, regardless of their general atta chment style for human interactions (Beck & Madresh, 2008), suggesting a stronger level of comfort with pets than with humans. This may imply that the benefits that could be unlocked by a companion animal with whom attachment exists, may be comparable, if not stronger, than the benefits that could be derived from exposure to a human attachment figure. This notion of attachment to pets, being in many ways stronger than our attachment to humans, has been supported by self report surveys which found that part icipants report relying on their dogs more heavily than any other supportive other (mothers, fathers, brothers, sisters, best friends, children), with the exception of romantic partner (Kurdek, 2009). Together these studies paint a picture of a stronger le vel of comfort with our relationships with non human attachment figures that is congruent with studies that have found differences in physiological reactivity between a pet and a close human friend. For example, when exposed to a stressful task, participan ts who were accompanied by a pet demonstrated lower physiological arousal than those who were accompanied by a close human friend ( Allan, Blascovich, Tomaka & Kelsey, 1991 ), suggesting that the social
5 aspects of our interactions with companion animals may be responsible for the various benefits associated with this interaction. In short, the reduction in blood pressure (Friedmann 1983; DeMello, 1999 ) and pain ratings (Hansen, et al, 1999; Havener et al., 2001; Braun, 2009 ) associated with exposure to famil iar as well as unfamiliar companion animals may be a result of the the Biophilia effect. However, it may simply be a result of an attachment, such that viewing an unfamiliar dog may be sufficient to trigger feelings of attachment that have been associated with other dogs. There is a very limited body of research that examines the differences in the effects of familiar (attachment present) and unfamiliar (attachment absent) companion animals on humans. The limited evidence we do have suggests that familiar dogs have a stronger effect on heart rate and blood pressure than do unfamiliar dogs (Baun, Bergstrom & Langston, 1984). Future research in this area may help to illuminate the mechanisms behind the various benefits associated with companion animals, by el ucidating the effects of attachment. The following review of the literature will include an investigation of (a) the psychological and physiological benefits associated with short term exposure to companion animals, (b) the psychological and health benefi ts associated with long term exposure to companion animals, (c) social support and attachment, (d) the Biophilia effect, and (e) the effects of human social support and exposure to companion animals on pain reduction.
6 Physiological and Psychological Ben efits Associated with Short Term Exposure to Companion Animals The mere presence of companion animals is sufficient to elicit physiological changes in humans, specifically in terms of heart rate and blood pressure. Generally, interaction with companion ani mals has been found to reduce arousal, lowering blood pressure and heart rate (Friedmann, 1983; DeMello, 1999). Even short term exposure to an unfamiliar dog has been observed to influence physiological measurements (Friedmann, 1983; DeMello, 1999). In on e particular study, Friedmann (1983) examined the effects of exposure to an unfamiliar dog on systolic blood pressure, diastolic blood pressure, and heart rate during a resting period, and a mildly stressful task (reading aloud). Participants between the a ges of 9 and 16 were attached to an automated blood pressure cuff and were given a 10 minute period in which to acclimate to the cuff before baseline readings of systolic blood pressure, diastolic blood pressure, heart rate and mean arterial blood pressure were collected. Each child was assigned to one of two conditions: dog present, or dog absent. Each participant was asked to rest for two minutes, then to read aloud for two minutes, with the order of these tasks randomly assigned. Among those in the dog p resent condition; the dog was either present for the first 2 minutes or the last 2 minutes. The simple presence of an unfamiliar dog was sufficient to reduce heart rate and blood pressure during both a resting period, and a mildly stressful task, such as r eading aloud (Friedmann, 1983). The effect of the pet was stronger when it was present from the beginning of the experiment than when it was added half way through the experiment. Friedmann (1983) suggests that the dog may alter the children's perception o f the experimental environment, making it less
7 stressful. Even though the dogs in Friedmann's experiment were "unfamiliar" to the participants, a dog is arguably still something of a familiar animal. One would expect that our personal familiarity with dog s, in conjunction with our long evolutionary history with dogs, would result in an increased sensitivity to dogs in comparison to non traditional companion animals. However, DeMello (1999) found that proximity to traditional (dog) and non traditional (goat ) companion animals had comparable effects on blood pressure and heart rate reductions following cognitive distress. DeMello (1999) induced cognitive distress by having participants complete three frustrating pencil and paper tasks. Between each task, the re was a rest period during which the research assistant left and returned with one of the following (in a counterbalanced order): a dog, a goat, or a book, which served as a control. Each participant completed one test in the presence of a dog and the res earch assistant, one in the presence of a goat and the research assistant, and one with the research assistant, who sat silently reading a book. The results of this experiment suggest that the mere presence of an unknown friendly animal, whether traditio nal (dog) or non traditional (goat), can significantly reduce physiological arousal in normotensive adults, following termination of a cognitive stressor. Reductions in blood pressure and heart rate during the rest period following termination of the cogni tive stressor were significantly greater in the condition where an animal was present. There was no significant difference between the physiological responses to the goat and the dog, suggesting that two vastly different species both possess the ability to reduce blood pressure and heart rate in humans.
8 Short term exposure to an unfamiliar companion animal has been found to reduce blood pressure (Friedmann, 1983; DeMello, 1999) and heart rate (Friedmann, 1983; DeMello, 1999) in humans, however few studies have taken into account the nature of the realationship. Baun, Bergstrom, and Langston (1984) conducted a study that examined the effects of familiar and unfamiliar dogs on physiological measures, including blood pressure, heart rate and respiratory rate. Participants for this study included 24 dog owners who had lived with the same dog for at least one year. Participants were attached to blood pressure, heart rate, and respiratory monitors and were instructed to sit quietly for 10 minutes while their blood pressure, respiratory rate and heart rate returned to baseline, after which baseline measures were collected. Each participant experienced three 9 minute blocks, presented in a counterbalanced order: petting own dog, petting unfamiliar dog, and reading si lently. Blood pressure, heart rate, and respiratory rate were recorded every three minutes throughout the experiment. There were significant differences in both systolic and diastolic blood pressure between petting a familiar dog, petting an unfamiliar do g, and reading silently. There was a significant effect of both protocol and time and a significant interaction between protocol and time. When participants were petting their own dogs they demonstrated the biggest decrease in blood pressure over time. For systolic blood pressure participants demonstrated a greater response to their own pet in the first three minutes, and a greater response to the unfamiliar pet in the last three minutes. This may be due to a greeting response that occurs with familiar dogs to a greater extent than unfamiliar dogs. There was no significant difference between familiar dogs and unfamiliar dogs on heart rate or on respiratory rate.
9 Overall, the findings from this study suggest that petting a familiar dog has a relaxation effect that is slightly stronger than silent reading, which results in a significant decrease in blood pressure. Petting an unknown dog produced a slight relaxation effect, weaker than the effects of silent reading and petting a familiar dog. Siegal (1990) sugg ested that the relationship between companion animals and physical health is an indirect relationship, mediated by the psychological benefits associated with companion animals, which in turn influence psychological and physical health. A number of studies have been conducted to observe what, if any, psychological benefits can be found by exposing individuals to animals for short periods of time. For many years it has been asserted that ownership of a pet can have emotional, social, and psychological benefit s to their owners. For example, Brodie and Bailey (1999) mentioned that animals appear to promote harmony and social happiness, while improving social interaction. They also noted that the presence of a companion animal can improve psychological well being by inducing higher levels of relaxation, and facilitating humor (Brodie & Bailey, 1999). However, many of the studies examined by Brodie and Biley (1999) involved interaction with a familiar companion animal, most of which were correlations of pet ownersh ip and depression/mood scores, which may be misleading due to the lack of information regarding directionality. Investigating the effects of short term interactions with companion animals can be more problematic in terms of methodology. Brodie and Bailey ( 1999) suggested that the lack of significant findings in many studies is indicative of weak methodology rather than a weak effect. Consider a study conducted by Phelps, Miltenberger, Jens, and Wedenson (2008)
10 that examined a group of five depressed elderl y patients living in a nursing home. During a baseline assessment period of 4 8 weeks, participants were evaluated on mood, depression, social interaction (with a roommate), and their satisfaction with the visit (from the nurse). Following the baseline obs ervation period, participants were given one 5 10 minute dog visit a week (with one of three dogs from a local obedience class) for a period of six weeks. The results suggested that there was a minimal improvement in depression scores, mood, or social inte raction after the intervention was introduced. Of the five participants, one demonstrated increased verbal and non verbal interactions with humans after the introduction of the dog visits, one demonstrated decreased negative mood, and one demonstrated incr eased positive mood. All of the participants displayed verbal and nonverbal interaction with the dog, and indicated that they would like to receive more dog visits in the future. On average, participants reported feeling happy as a result of the visit, and indicated that they were looking forward to the next visit slightly more than neutral. The trends that were found did not generalize to the days when the dogs were absent, suggesting that a larger sample size may result in significant differences between a treatment group and a control group. In a similar study, Jessen (1996) investigated the effects of an avian companion on depression, loneliness, and moral levels of 40 older adults residing in a skilled rehabilitation unit. Pretest measures of morale, depression, and loneliness were collected before the intervention. For those in the experimental group, a small cage containing one budgerigar was placed in the corner of their room for 10 days. Following the 10 day intervention, post test ratings of depre ssion, loneliness and morale were collected. Although there were no
11 significant changes from pretest to posttest on ratings of morale and loneliness (though there was a trend toward improved loneliness and morale scores), there was a significant decrease i n depression, such that those in the treatment group had a greater decrease in depression than those in the control group. This finding of reduced depression is in line with Siegal's (1990) notion that the physiological benefits associated with companion a nimals may be an indirect result of the psychological benefits received from such interactions. Benefits Associated with Long Term Exposure to Companion Animals Research into the benefits of long term exposure to companion animals has been difficult, due to the fact that participants cannot be randomly assigned to be pet owners. For this reason a large portion of the research is focused on short term exposure, or is simply correlative. Nonetheless, a few studies on the long term effects of pet ownership ha ve demonstrated extensive health benefits over numerous fields of human health, including but not limited to general health (Dembicki & Anderson, 1996; Raina, Waltner Toews, Bonnett, Woodward & Abernathy, 1999; Enders Slegers, 2000), number of reported doc tor cisits (Siegal, 1990; Heady, 1998) survival rate following heart complications (Friedmann & Thomas, 1998), and mental health and well being (Budge, Spicer, Jones & George, 1998). For example, Siegel (1990) conducted a study that investigated the eff ects of pet ownership on the total number of doctor visits in a year. Data were collected as part of a 1 year panel study investigating the health behavior of elderly patients. Interviews were conducted by telephone. During the first telephone interview, p articipants were asked to supply information regarding their health status, health beliefs, chronic health problems, psychological distress, social network size and support, pet ownership, pet type,
12 demographic characteristics, depression, and recent life events. For the 12 month period following the baseline interview, respondents were given follow up interviews every two months concerning doctor contacts that had occurred since the prior interview. For pet owners, information on the nature of their relat ionship with their pets, including information relating to attachment, was collected two months after the initial interview. Measures of depression and life events were collected at the initial interview as well as 6 and 12 months later. The results of th is study suggest that pet ownership (particularly dog ownership) has a strong influence of the number of physician visits by elderly owners, such that pet owners had fewer doctor visits in a year than non pet owners. This effect was stronger for patient in itiated visits than for physician initiated visits. This may suggest that people with dogs are healthier to begin with, as owning a dog requires physical activity, however the significant effect of pet cats combats this hypothesis. Alternatively, the pets may serve as a stress buffer for their owners. Stressful life events were associated with more doctor visits in non pet owners, but not in non owners. This effect was stronger for dog owners than owners of any other type of pet. Accumulation of stressful l ife events had no effect at all on the annual number of doctor visits by dog owners, while it increased the number of doctor visits in non dog owners. However, this study was limited in that it cannot prove causation. The effects of stressful life events o n non pet owners could again be indicative of a health disparity between groups, such that those who are likely to own dogs are likely to be in better health, and thus would be better equipped to combat stressful life events. However the slight difference observed between dogs and cats may be due to differences in the way we
13 relate to dogs and cats, rather than differences associated with owner health. Beck and Madresh (2008) found that cat owners experience significantly more relationship anxiety than do d og owners, suggesting that this relationship may have weaker effects. Similarly, a one year longitudinal study conducted by Raina, Waltner Toews, Bonnett, and Abernathy (1999), examined the effect of pet ownership on changes in physical health of older, no n institutionalized adults. The investigators also examined the relationship between human social support and pet ownership and attachment. Each participant received a questionnaire by mail, which contained socio demographic questions, questions related to pet ownership, chronic health conditions, and major life events. Participants completed and returned the questionnaires, and were sent the same questionnaires a year later. For those without pets physical health declined to a greater extent than did the s cores of pet owners. This effect was observed in cat owners as well as dog owners, suggesting that it may simply be the caretaking role, rather than shared activities, that keep pet owners active. When taken in conjunction, these studies seem to suggest th at owning a pet, especially a dog, can significantly reduce the number of patient initiated doctor visits. However, this may be due to a reduction in the subjective pain experienced (Havener et al., 2001; Braun et al., 2009) or it may be due to stress buff ering ( Siegel 1990), suggesting a psychological link Additionally, this effect may be due to the increased activity associated with caring for a pet. Caring for a pet may be sufficient to improve health by increasing activity level. Alternatively, there m ay be a difference between pet owners and non owners in that healthier people are more likely to possess the ability to care for a pet, and thus
14 would be more likely to have a pet. Much like the short term benefits associated with exposure to companion an imals, it is postulated that the long term health benefits may be an indirect effect, mediated by the improved mental health that is associated with dog ownership. Budge et al. (1998) conducted a study examining the association between health, both physica l and psychological, and pet attachment, pet ownership, pet compatibility, and human social support. Participants completed five questionnaires, relating to compatibility, attachment, interpersonal support, mental health, and physical symptoms. Stronger c ompatibility between pet and pet owners was significantly correlated with better overall mental health, a greater sense of well being, more positive affect, and less anxiety and distress. Stronger compatibility was also associated with improved physical he alth measures such that those who were more compatible with their pets reported fewer ill health symptoms. The correlation between compatibility and owner health was stronger than that of pet attachment and owner health and social support and health. Howev er, there was still a significant correlation between pet attachment and positive affect and pet attachment and overall well being. Building on these observations, companion animals' status as valuable social resources is solidified by their association w ith trust, autonomy, social competence, and unconditional love (Kurdek, 2009). Moreover, they have the capacity to serve as a playmate, confidant, and friend. There is a great deal of experimental evidence in support of the notion that keeping proximity to animals may result in numerous benefits including but not limited to those associated with adaptation and coping (Spence & Kaiser, 2002). Spence and Kaiser
15 (2002) suggest companion animals may be employed as a resource, in turn lowering the perception of demands, and improving coping and level of adaptation. The phenomenon can be further explained through social support and attachment theories. Social Support and Attachment There is a myriad of evidence that describes the positive health benefits of social companionship including having a confidant ( Kroenke Kubzansky Schernhammer Holmes & Kawachi, 2006) and being married (Kidd & Feldman, 1981). Recent evidence has found that social support networks may be extended to include companion animals. Thus, soc ial support theory can be examined as one possible explanation for the unique interspecies bond that exists between humans and companion animals, specifically pet dogs. Numerous survey studies have found that people say that they consider their pet to be a member of the family," (Turner, 2001; Cohen, 2002; Beck & Katcher, 2003; Chur Hansen et al., 2009). Other studies have found that participants report relying on their dogs more heavily than any other supportive other (mothers, fathers, brothers, sisters, best friends, children), with the exception of a romantic partner (Kurdeck, 2009). Social support, and attachment provided by companion animals may be the source of the comfort that is associated with the human companion animal bond. It is quite ordinary to hear people enthusiastically admit to feeling close emotional ties to their pets, and considering them to be a part of the family. Furthermore, it has become customary to use the term attachment to describe this relationship. Although Bowlby's attachmen t theory was based on human relations, it can be very easily applied to trans species attachment. Crawford and Warsham (2006) defined attachment as "A form of
16 behavior resulting in an individual seeking or maintaining proximity to another, clearly specifie d individual, who functions as a secure base and who is perceived as better able to cope with life's stressors" (p. 99). The definition of attachment in terms of the relationship between companion animals and humans is much more controversial than those d efinitions based on relationships between humans. Budge, Spicer, Jones and George (1998) defined human companion animal attachment as "the emotional bond felt and expressed between a pet and its owner" (p.219). Yet Keil (1998) defined the same construct, h uman companion animal attachment, as the "Hierarchical relationship between a human and an animal, which could be any living thing other than a plant or another human" (p. 126). These inconsistencies make it difficult to draw direct comparisons between att achment to humans and attachment to companion animals. Fortunately, more and more researchers are working to empirically compare trans species attachment with attachment bonds between two humans. In attachment theory, infants seek proximity to their attach ment figure. Many pet owners describe behaviors that are consistent with proximity seeking, including reports that they seek comfort in their pet's company when things go wrong (Heady, 1999). Seeking proximity is a trademark of attachment in human interact ions. The pleasure many pet owners feel when holding or petting their pet may be a manifestation of proximity seeking. Many owners report enjoying these activities (Enders Slegers, 2000), however it is important to note that enjoying petting or holding a p et does not encompass all aspects of proximity seeking, let alone attachment in general. This relationship appears bidirectional, in that is it quite common for dogs to seek proximity to their human attachment figure and
17 vice versa (Parthasarathy & Crowell Davis, 2006). Kurdek (2009) found that in relation to attachment to dogs, participants rated secure base (accounting for 39% of bond) as the most important factor, followed by safe haven (36%). This suggests that these factors are not only an important fa ctor in human relationships, but are also important for human companion animal attachment. Chur Hansen et al. (2009) conducted in depth, open ended interviews with 11 women ages 65 and up regarding how they feel about their relationships with their pets. For the purposes of this study, attachment was defined as "Love for the pet and the desire to maintain close physical proximity to their companion animal" (Chur Hansen et al., 2009, p. 288). After transcribing and coding the interviews 10 themes appeared i n nearly all of the interviews. These themes were attachment, speaking about the pet as a family member, expressing a preference for animals over people, difficulty of living without a pet, companionship, the need to care for someone, physical benefits ass ociated with taking care of a pet, not wanting to leave the pet, bereavement and grieving in relation to the death of a pet, and the expenses associated with owning a pet. These themes overlap considerably with elements of human attachment, which led Chur Hansen et al. (2009) to the conclusion that attachment is an appropriate term that may be used to describe the relationship between people and their companion animals. This conclusion was based on the numerous comparisons participants drew between attachme nt to their pets and attachments to humans and the fact that many of the interviews had themes that resembled aspects of attachment to humans such as not wanting to leave the pet, difficulty of living without a pet, and the need to care for someone.
18 Attac hment to pets may serve many adaptive purposes, including functioning as a surrogate for human attachment. Much of the literature on the human companion animal bond describes pets as being a part of the family (Turner, 2001; Cohen, 2002; Beck & Katcher, 20 03, Chur Hansen, et al, 2009). However, most of these articles do not have any standardized way of defining what this means. The US Census defines family to be "a group of two people or more (one of whom is the householder) related by birth, marriage, or a doption and residing together" (U.S. Census Bureau, 2000; as cited by Cohen, 2002). There are few operational definitions of family that can include pets. However many survey studies have found themes that suggest a familial relationship between pets and t heir owners (Turner, 2001; Cohen, 2002). Cohen (2002) found evidence that pets are members of the family unit. This was accomplished through an analysis of the precise role that pets play in urban American families and how this role compares to that of hu man family members. During Phase 1 participants were asked identical questions about the pet and the human family member whom they felt closest to, which included questions about loneliness and the strength of the relationship. In Phase 2, participants wer e asked to answer questions regarding their social networks and questions designed to compare the feelings toward a pet to the feelings toward a human. This was done by randomly assigning participants to be in the condition where they describe human family members, or companion animals. The results of these surveys suggest that pets are full fledged members of the family. Differences between men and women were much more pronounced in Phase 1 than in Phase 2. Women were more likely to give stronger reports of love in both human and pet
19 relationships, and thus their scores were higher for both human relationships as well as pet relationships. The attachment we feel towards our pets appears to be similar in nature to the attachment bonds we feel towards other humans. This confirms a notion that has long been supported by anecdotal evidence. Furthermore, there is a great deal of anecdotal evidence that suggests that people utilize relationships with pets to compensate for a lack of human attachment. Turner (20 01) conducted a study in which in depth semi structured interviews regarding the recent euthanization of a companion animal were recorded and analyzed. In seven out of eight interviews, participants repeatedly referred to the pets as members of the family. Two of the three women who had not had children had described their pets as being like children to them. The women who did have children emphasized the difference between the relationships they had with their companion animals while their children were li ving at home, and the relationships they had with their companion animals before the birth of their children or after their children had moved out. These women stated that they were much closer to their pets during times when they did not have a child to n urture. This suggests that women form surrogate attachment bonds with companion animals to compensate for a lack of attachment with their children. Further examining the concept of inter species attachment, Kurdek (2009) conducted a study that investigate d the extent to which attachment and safe haven contribute to the affective bond between humans and their pet dogs. Participants completed an online survey containing demographic questions as well as measures of Features of Attachment for Pet Dogs (Kurdek, 2009), safe haven, self disclosure and need satisfaction.
20 Secure base was found to account for 39% of the relationship between owner and pet dogs while safe haven accounted for 36% of the bond (Kurdek, 2009). When compared directly with family members, pa rticipants responded that they rely on their dogs as a form of social support more than any other supportive other (mothers, fathers, brothers, sisters, best friends, children), with the exception of romantic partners who were rated slightly higher than pe t dogs. Those with low levels of self disclosure rated dogs equivalently to partners. This study indicates that dogs can function as attachment figures. Although the aforementioned studies have found many similarities between the relationships we share wi th people and those we share with companion animals, there are also many differences between these relationships. Many people may be more able to form secure attachments with pets, than they can with other humans (Beck & Madresh, 2008). Secure attachment s tyle is defined as the development of comfort with interpersonal closeness and a willingness to depend on others (McWilliams & Bailey, 2010). In contrast to secure attachment style, insecure attachment styles include anxious attachment, which is characteri zed by a tendency to be anxious regarding the possibility of social rejection, and avoidant attachment style, which is characterized by a discomfort with close relationships. Attachment may serve as a protective factor for many situations associated with d istress. Pets may be able to influence health by serving as a secure attachment figure. Previous research has found that those who form secure relationships are likely to be healthier than those who form avoidant or anxious attachments (McWilliams & Baily, 2010 ). Beck and Madresh (2008) conducted a study investigating the strength of the attachment bonds that exist between two humans and between humans and pets. Participants
21 completed questionnaires containing two modified relationship scales, and a measure of attachment style. The vast majority of participants were securely attached to their pets regardless of their general attachment style for human interactions. This may be due to the very different experiences that come to be associated with romantic par tners and pets. The high level of dependence of pets makes this a low risk relationship given the fact that a pet cannot abandon you in the way that a partner can. Those with more dogs reported less relationship anxiety and less avoidance with their pets. While this may simply be due to the fact that these people own more dogs because they enjoy the company of dogs more than those who choose to own fewer dogs, or it may be due to a deeper difference. Cat owners reported more relationship anxiety than non pe t owners and dog owners. There was a strong significant finding suggesting that relationships with dogs are less insecure, overall, than relationships with romantic partners. This may reflect that it is emotionally safer to love a pet than a partner, as pe ts are more dependent in general. This suggests that the health benefits that have been observed with pet ownership may be associated with the attachment bond that exists between people and their pets. Attachment style has a strong influence on health ( Mc Williams & Baily, 2010 ), suggesting that the health benefits that have been observed in conjunction with pet ownership may be associated with the secure bonds that often exist with this type of relationship. Public use data from the National Comorbidity Su rvey Replication (NCS R) was used to assess demographic information, attachment style, chronic health conditions and psychiatric disorders. Insecure attachment style was positively associated with about half of the health conditions that were investigated in this study (McWilliams & Baily,
22 2010). There were significant differences between those with anxious attachment style and avoidant attachment style such that those with an ananxious attachment style were more likely to have a wider range of medical cond itions and more severe medical conditions than those with an avoidant attachment style. High ratings on avoidant attachment were significantly associated with conditions that involve pain symptoms. In contrast, those with higher ratings on anxious attachme nt were more likely to have conditions that involve the cardiovascular system, such as high blood pressure, heart attack and stroke (McWilliams & Baily, 2010). When analyses adjusted for histories of psychiatric disorders, only the association between anxi ous attachment style and various forms of chronic pain remained statistically significant. The authors suggest that the association between anxious attachment style and cardiovascular illnesses may be a long term health consequence of a lifetime of anxious attachment style. This is supported by the fact that anxious attachment style is positively associated with elevated blood pressure during social interactions (Gallo & Matthews, 2006). It is logical that insecure attachment would lead to various ailments; however, this study does not prove causality. It remains possible that poor health could lead to relationship distress, which could in turn lead to insecure attachment. The attachment bond people feel towards their pets may be responsible for the various effects that have been observed during exposure to companion animals. However, the Biophilia hypothesis provides an alternative explanation for these effects, suggesting that these effects may be a result of an evolutionary predisposition to seek comfort from living things.
23 Biophilia The importance of animals to human survival over the past 2.6 million years has shaped our evolution such that we are predisposed to seek comfort from non human animals. This tendency to seek comfort from nature, including both plants and animals, is the basis behind Wilson's (1984) Biophilia hypothesis. The Biophilia hypothesis was originally defined as the "Innate tendency to focus on life and life like processes" (Wilson, 1984, p. 1). Wilson's original theory encompassed all forms of nature, which may be somewhat misleading because our ancestors had multiple interactions with nature, many of which were deleterious. For example, it is evolutionarily advantageous to be fearful of poisonous plants and animals such as snakes, spiders, poison ivy, and oleander; however, this is not the case with living food items such as game animals and edible plants. Wilson later revised his theory, to examine Biophilia, not as a single instinct, but as a complex set of rules, applying to diff erent situations, that may be analyzed individually (Wilson, 1993, p. 3). Biophilia overlaps with evolutionary psychology in that the Biophilia hypothesis states that humans are hardwired to attend to animals and plants due to the fact that survival for th e past several million years has often been dependant on finding animals to hunt (Beck, & Katcher, 2003). Howell, Dopko, Passmore, and Buro (2011) examined correlations between nature connectedness as defined by the Connectedness to Nature Scale and the e motional, psychological, and social aspects of well being. This study found that when social
24 desirability was controlled for, there was a positive correlation between nature connectedness and psychological well being, and there was a positive correlation b etween nature connectedness and social well being. These correlations remained significant during a follow up study which used various nature connectedness scales. All three nature connectedness scales correlated significantly with psychological well being and with social well being. Two of the three correlated significantly with emotional well being. This finding suggests that connectedness with nature is associated with positive well being. This finding does not explain directionality; however, subsequent experiments have found that exposure to natural landscapes results in improved affect (Valtchanov & Ellard, 2010), and reductions in physiological arousal (Ulrich, 1991). Valtchanov and Ellard (2010) found that exposure to natural landscapes can reduce negative affect. Furthermore, they found that the restorative effects associated with nature can be accessed through virtual reality (Valtchanov & Ellard, 2010). Stress and negative affect were induced in all participants before they were randomly assigned to explore one of three virtual environments for 10 minutes: Virtual natural landscape, virtual cityscape, and an environment composed of geometric shapes. Participants in the natural landscape condition demonstrated significantly lower stress levels, and significantly improved affect when compared to those in the geometric shape condition and those in the cityscape condition. This suggests that exposure to natural environments may have a restorative effect following times of distress. Ulrich (1991) found that virtual emersion in natural landscapes significantly reduced recovery time following a cognitive stressor (viewing a stressful film)
25 in comparison to emersion in an urban landscape. Virtual emersion involved having participants watch a video of a nat ural landscape or an urban landscape. Recovery time was quantified using physiological readings of heart rate, muscle tension, skin conductance, and pulse transit time (which is highly correlated with systolic blood pressure). This study found that those v iewing videos of a natural landscape had a significant reduction in all four physiological readings in comparison to those who were exposed to videos of urban environments. This suggests that exposure to natural landscapes can significantly reduce physiolo gical arousal following times of distress. Exposure to natural landscapes also possesses the ability to reduce subjective accounts of pain. Diette, Lechtzin, Haponik, Devrotes, and Rubin (2003) investigated the effects of exposure to natural sounds and la ndscapes on subjective accounts of pain and anxiety by patients undergoing a bronchoscopy, a painful procedure. Participants in the treatment group were played a tape of nature sounds before, during, and after the procedure, and were presented with a bedsi de mural depicting a natural landscape. The exposure to the nature stimulus had no effect on anxiety, in comparison to the control group. However the exposure to nature did significantly reduce participant's physiological arousal during exposure to pain ev en when all other factors, including age, health, and pain medications, were controlled for. When taken together, the results of these experiments suggest that exposure to nature has the ability to reduce subjective experiences of pain (Diette, et al., 200 3), in addition to physiological measures (Ulrich, 1991), improved affect and lowered stress (Howell et al., 2011). Wilson (1984) originally described the Biophilia effect as an effect of nature in
26 general, which included effects of both plants and anima ls. In examining the therapeutic effects of companion animals it is important to take note of the effects associated with attachment in addition to the effects of Biophilia. Our relationship with companion animals provides a unique example of human's rela tionship with nature due to the strong emotional bond that exists (Cohen, 2001; Turner, 2002; Beck & Madresh, 2008; Kurdek, 2009). Further complicating matters, is the fact that reduced physiologic arousal, improved psychological well being, and reduced pa in have been observed with proximity to companion animals (Friedmann, 1983; Baun et al., 1984; Jessen, 1996; DeMello, 1999; Hansen et al., 1999; Havener et al., 2001; Braun, 2009;) in addition to proximity to natural landscapes (Ulrich, 1991; Diette, et al ., 2003; Howell et al., 2011 ). Few studies have directly compared these effects making it difficult to assess their relative strengths. Pain Reduction Associated with Exposure to Companion Animals vs. Human Social Support Much like exposure to natural sti muli, exposure to companion animals may have the capacity to reduce subjective experiences of pain. This may be due to an effect of the natural stimuli, or it may be an effect associated with attachment. Numerous studies of human attachment have found that attachment may serve as a buffer to stressful or painful situations (Brown, Sheffield, Leary & Robinson, 2003; Master et al., 2009; Eisenberger, Master, Ingaki, Taylow, Shirinvan, Liberman & Maliboff, 2011). This attachment bond may account for the numero us psychological, physiological and physical benefits associated with proximity to companion animals. Animals may serve as a source of social support, causing a reduction in perceived pain.
27 Braun ( 2009 ) conducted a study aimed at determining the impact of Animal Assisted Therapy (AAT) as a pain intervention for children between the ages of 3 17, who had visited an acute care pediatric facility. Participants were included in this study if they reported their pain as a 2 or more on the FACES pain scale. Part icipants were placed in the control group if they were fearful of or allergic to dogs or if the dog was not present during the time of their visit, and were placed in the experimental group if the dog was present during their visit and they had no allergie s or fears of dogs. The final number of participants was 57, only 18 of which were in the intervention group. At the start of the study, baseline measures of pulse, blood pressure, and respiratory rate were recorded, and pain level was recorded based on t heir self report using the FACES pain scale (0 10). Those in the intervention group underwent a 15 20 minute session with the AAT dog and handler. The handler sat quietly, as not to influence the interaction. At the end of the 15 minute session the dog and the handler left and post test readings of pulse, blood pressure, self reported pain level and respiratory rate were collected. Those in the control group underwent the same baseline measures and were asked to sit quietly for 15 min, after which, the post test measures were collected. Information related to pain were collected from the child's medical records, including date of admission to the hospital, acute and chronic illness history, pain history including pain assessment ratings, interventions to rel ieve pain, and effectiveness of the pain interventions. Braun (2009) found very strong evidence for their hypothesis that the presence of a therapy dog can effectively reduce pain in children ages 3 17. The reduction in pain in the experimental condition as determined by the FACES pain scale was four times that of the
28 control group. "The pain reduction experienced within 15 min by these children [the experimental group and the control group] is comparable to the use of oral acetaminophen with and without c odeine in adults." (Braun, 2009, p. 108) The only unexpected finding was a slight increase (2 breaths/min) in respiratory rate, which may have been due the unanticipated excitement of seeing a dog in an acute care center. There was no significant differenc e between the experimental and control group for heart rate or blood pressure though there was a significant difference for pain on the FACES scale, such that those in the experimental condition reported less pain than those in the control group. Hansen et al., (1999) conducted a similar study examining the effects of the presence of a therapy dog on patient distress during a medical examination. For the purposes of this study, patient distress was defined as physical manifestations of pain including but no t limited to flailing limbs and crying. Participants for this study included thirty four children between the ages of 2 and 6 years old, who had visited the pediatric clinic on the days of data collection. Participants were at the clinic for an assortment of ailments. Participants in the experimental condition were presented with an unfamiliar dog when they entered the treatment room and told that they could interact with the dog as they desired (most participants chose to pet the dog). Each participant w as accompanied by one or both parents and 2 experimenters for the entire time they were in the exam room. Baseline measures of physiological and behavioral data were taken before the examination began. During the examination blood pressure, heart rate and peripheral skin temperature were recorded every 2 minutes. Each examination was recorded by videotape, to be coded later for visible manifestations of actual or perceived pain.
29 Participants who underwent the examination with the therapy dog displayed sig nificantly fewer manifestations of pain than those who underwent the examination without the therapy dog. Furthermore many mothers made comments regarding how relaxed and well behaved their children were when the dog was present (as compared to average doc tor visits). Overall these results suggest that companion dogs may be useful in reducing pain in children. Further research is warranted to determine whether or not this can be generalized to other age groups. Similarly, a study carried out by Havener et a l. (2001), examined the effect of an unfamiliar dog on children undergoing dental procedures. Participants for this study included 37 dental patients ranging in age from 7 11 years old. Prior to the dental visit, demographic information was obtained on eac h child's age, gender, race, presence of pets in the home, relationship with pets, past experiences and fear of dogs, and feelings about coming to the dentist. Those who had a fear of dogs were excluded from the study. Participants were recorded on audio a nd video so that they could be coded for behavioral distress, which included crying, limb flailing, and other physical manifestations of pain. Physiologic arousal was measured every 5 minutes using peripheral skin temperatures. As soon as participants were positioned in front of the camera, the dog was positioned on a small bench near the child's right shoulder. Each participant was encouraged to touch, pet and talk to the dog as desired. Havener et al. (2001) found that the children with the dog experienc ed a slight increase in skin temperature while waiting for the dentist, while those in the control group experienced a decrease in skin temperature. Participants in the control group had a sharper
30 decline in skin temperature than those in the experimental condition. The cooler temperatures indicate more distress and pain, suggesting that the treatment may have been effective. These differences were not statistically significant when taken by themselves; however, when the results of the children with higher dental phobia were taken separately from the rest of the children, they found that children who were most stressed about coming to the dentist experienced significantly less physiologic arousal when the dog was present than those in the control group. This suggests that animal assisted therapy is most effective in decreasing arousal, during circumstances where arousal is high from the start. The reduced reactivity to pain that has been observed with exposure to companion animals may be associated with the a ffective bond people feel towards companion animals, as many similar effects have been observed in studies of human attachment. In their experimental study on pain perception, Brown et al. (2003) found that social support either from a friend or a stranger could significantly reduce the amount of pain experienced. Two participants, each accompanied by a friend, reported to each session. The friend of each participant served as the stranger for the other participant. The supportive others were given differen t instructions depending on their condition. Those in the active support condition were told to support the participants as much as possible before and during the task. Those in the passive support condition were instructed not to speak or make eye contact with the participant; their support was based on their presence. Those in the interaction condition were instructed to interact with the participant as much or as little as they desired. The participants spent three minutes in a waiting area either alone or with a supportive other, while the experimenter set up the cold pressor task, a device used to induce low levels of
31 pain through exposure to cold. Participants were asked to place their non dominant hand in the cold water, which was sustained between o ne and two degrees Celsius. They were asked to refrain from moving their hand and to keep it in the water until it became uncomfortable or until 3 minutes had elapsed. Participants rated the pain on a 10 point scale every 20 seconds. Participants were aske d to rate the supportive behavior of each supportive other to ensure that they were following directions. Participants in the active support and passive support conditions reported less pain than the participants in the alone and interaction conditions re gardless of whether or not the supportive other was a stranger or a friend. There were no significant differences between the active support and passive support conditions. Those in the interaction condition reported more pain than participants in either o f the support conditions (active or passive). This may be due to the fact that there may have been negative transactions in the interaction condition. Differences between the interaction and support conditions did not appear until 60 seconds after the cold pressor task began. This may suggest that the positive effects of social support may not be immediate, or that the positive effects of social support may only be observed in situations where the discomfort is significant. These findings suggest that socia l support may reduce the amount of pain we experience regardless of the person providing that support. However, it is important to take into consideration the degree of attachment, which was not evaluated by this study. Kurdek (2009) found that people repo rted stronger attachment to their significant others and family members than their friends. The attachment between the friends may not have been strong enough to result in
32 differences between groups. Subsequent studies have found significant differences b etween our reactions to pain when exposed to strangers versus loved ones. Master et al. (2009) found that viewing a loved one's photograph can have pain attenuating properties. Participants for this study were 25 right handed women who were currently in lo ng term relationships. Each participant was brought to the testing room while her partner was brought to a separate room and was photographed. Each participant's baseline pain threshold to thermal stimulation was recorded once their pain level reached a 10 on the 20 point pain rating scale, which corresponded to "moderate discomfort." The thermal stimulation was applied to the left arm behind a curtain. Six stimulations, each separated by 20 second intervals, were given during each of seven conditions (each of which was presented twice): holding partner's hand, holding male stranger's hand, holding an object, viewing a partner's photographs, viewing a male stranger's photograph, viewing photographs of an object (chair), and viewing a fixation crosshair (no m anipulation). Unbeknownst to the participants the thermal stimulation was not consistently at the participants' pain threshold. Half of the thermal stimulations were delivered at the pain threshold, the other half were delivered at 1C above the participan t's pain threshold. The participants rated the unpleasantness of each stimulation by pointing to a number on the pain scale. To address the competing hypothesis, that social support reduces pain because it is distracting, participants' reaction times to co mputer generated beeps were recorded. The beeps occurred infrequently, and were randomly dispersed throughout the study. If one condition were inherently more distracting than the others that condition would have a longer reaction time to the beeps.
33 Maste r et al. (2009) found that the manipulations were not differentially distracting. In addition, they found that partner handholding led to significantly lower pain ratings than stranger handholding or object holding. The photograph condition found similar r esults, with partner photographs corresponding to lower pain ratings than stranger photographs, or object photographs. The pain ratings in the partner photograph condition were marginally lower than those in the partner handholding condition, suggesting th at a photograph may be even more effective in reducing pain than partner handholding. Eisenberger et al. (2011) conducted a follow up experiment in an attempt to elucidate the mechanisms behind the reduced pain ratings that have been observed in the prese nce of an attachment figure. This was achieved by allowing participants to view photographs of their romantic partners during experimentally induced pain while an fMRI scan was performed. The experimentally induced pain, and the establishment of a pain thr eshold was identical to that employed by Master et al. (2009). Participants for this study included 17 females in long term committed relationships, who reported to the lab with their partners. During the first phase of the experiment the partner was seque stered and photographed from four standard angles, while pain threshold for each participant was determined. Each participant was shown a series of three blocks (in a counterbalanced order). Each block contained images of one of the following: the partici pant's partner, a male stranger (similar in appearance to partner) and an object (chair). Each run was 80 seconds long and displayed various images of the particular stimuli. During each block participants received a series of four thermal stimulations (tw o moderate and two low) to their left
34 forearm. Following each thermal stimulation, participants were asked to rate their pain using a trackball device, which corresponded to the pain rating scale. Viewing an attachment figure during physical pain was asso ciated with elevated activity in the ventromedial prefrontal cortex (VMPFC) (a brain area associated with learned safety), reduced activity in the dorsal anterior cingulate cortex (dACC) (a brain region associated with pain) and lower pain ratings when com pared to both control groups (object and stranger). This was particularly true during the high pain sessions. Furthermore, participants who had been in relationships for longer periods of time had greater activation the VMPFC. Greater activity in the VMPFC (associated with viewing attachment figure) was associated with reduced pain rating and reduced activation in the dACC. These data suggest that viewing an attachment figure may serve as a safety stimulus to reduce the perception of physical pain and psych ological stress. Social support from a human (Brown et al., 2003), in addition to exposure to a companion animal (Hansen et al., 1999; Havener et al., 2001; Braun et al., 2009) have both been found to reduce subjective pain experienced by participants. A llen, Blascovich, and Mendes (2002) were able to directly compare these two effects in their examination of cardiovascular reactivity and pain tolerance in the presence of pets, friends and spouses. Participants in this study were 120 married couples eithe r with or without one pet (cat or dog). All participants were healthy and employed full time. The experiment took place in the home of each participant, providing a natural and comfortable environment. Participants entered a closed room either alone (with experimenter out of eye sight but in room), with a spouse, with a friend, or with a pet. In the spouse and friend condition,
35 the spouse or friend was seated across from the participant at a 90 degree angle about three feet away. They were told that the pu rpose of the experiment was for them to provide social support. In the pet condition, the pet was allowed to roam freely throughout the room. The humans were told explicitly to be supportive while the pets did not receive any such direction. Participants w ere attached to heart rate and blood pressure monitors, and then allowed to sit for 10 minutes while they acclimated to the machine. Following this period baseline measures were collected every minute for a 10 minute period. Each participant was given both a pencil and paper math task and the cold pressor task. The order of these tasks was counterbalanced for half of the participants. The results of this experiment suggest that pets can effectively buffer reactivity to acute pain and cognitive distress. Re lative to non owners, pet owners had significantly lower resting heart rate, systolic and diastolic blood pressures, exhibited lower reactivity (heart rate, systolic blood pressure and diastolic blood pressure) during both the arithmetic task and the cold pressor task, and returned to baseline levels more quickly. Non owners demonstrated the lowest reactivity when alone and the highest reactivity in the presence of their spouse. In contrast, pet owners demonstrated the lowest reactivity in the presence of t heir pet and the highest reactivity in the presence of their spouse. Those in the pet present condition performed faster and made fewer errors in the arithmetic task, than participants who were not tested with pets in the room. In the condition where both a spouse and pet were present the blood pressure and heart rate responses were less than the spouse alone but more than the pet alone, suggesting that the introduction of the pet lowered reactivity. During the cold pressor task, pet support was associated with the lowest reactivity, though
36 the presence of a spouse or friend was not as detrimental as it was in the math task. Exposure to one's pet can reduce physiological reactivity to pain and cognitive distress significantly more than exposure to a spouse o r a friend, suggesting that pets may serve as a better form of social support than human social network members during times of pain or distress. The Current Study Recent research has suggested that animal assisted activities can be effective at reducing blood pressure (Friedmann, 1983; Vormbrock & Grossberg, 1988; Straatman, Hanson, Endenburg, 1997; Friedmann, et al. 2007), heart rate (Friedmann, 1983, Straatman, et al, 1997; Vormbrock & Grossberg, 1988) and may also serve as an effective pain interventio n (Hansen et al., 1999). A similar pattern can be observed over long term interactions with pets, such that owning cats, and to a greater extent, dogs, has been associated with a reduction in doctor visits (Siegal, 1990). Although research has demonstrated that the presence of companion animals can have a therapeutic effect on people (Friedmann, 1983; Siegal, 1990; Hansen et al, 1999; Berget et al., 2008), it remains unclear why this is the case (Somerville et al., 2008). The Biophilia hypothesis, first pro posed by E.O. Wilson (1984), states that humans have an innate tendency to focus, and seek comfort from life and life like processes. Berget et al. (2008) suggest that evolutionary psychology and the Biophilia effect may be responsible for some of these be neficial effects associated with exposure to companion animals. Others have suggested that the therapeutic effect may be due to the attachment bond that exists between humans and companion animals (Beck & Katcher, 2003; Wood et al., 2005).
37 Exposure to hum an attachment figures has been found to reduce subjective pain ratings. Master et al. (2009) found that looking at photographs of a romantic partner during experimentally induced pain significantly reduced the amount of pain experienced when compared with viewing photographs of strangers, holding a stranger's hand and holding an object. Furthermore viewing a photograph of a romantic partner reduced subjective pain ratings marginally more than holding a romantic partner's hand. The results of this study sugg est that viewing a photograph of an attachment figure is sufficient to reduce subjective pain ratings. This effect was not observed when participants viewed photographs of strangers. Kurdek (2009) found that pets served as stronger attachment figures to th eir owners, than their mothers, fathers, sisters, brothers, or best friends. Furthermore, Baun et al. (1984) found that there was a significant difference in blood pressure and respiratory rate between participants petting their own dog and participants pe tting an unfamiliar dog, suggesting an effect of attachment. Thus, it is reasonable to hypothesize that participants will have different physiological reactions when exposed to photographs of their own pets as opposed to photographs of unfamiliar pets. Th ere is a very limited body of research that compares the effects of familiar (attachment present) and unfamiliar (attachment absent) companion animals on pain threshold and physiological reactions to pain in humans. Furthermore, there is a lack of research comparing the effects of animals and plants on these measures. Conducting such research may help to illuminate the mechanisms behind the various benefits associated with proximity to companion animals.
38 The current study examined differences in heart rate, blood pressure, and pain ratings between participants viewing photographs of their own dog, participants viewing photographs of a stranger's dog and participants viewing photographs of a plant. It was hypothesized that viewing photographs of any pet (fami liar or unfamiliar) would lead to the lowest physiologic reactivity, and subjective pain ratings in comparison to viewing a chair and a plant. Viewing photographs of a plant was expected to demonstrate lower physiologic reactivity and subjective pain ratin gs in comparison to viewing a chair, and higher physiological reactivity and pain ratings in comparison to viewing dogs (familiar or unfamiliar). Additionally, it was anticipated that viewing a familiar dog would result in physiologic reactivity and subjec tive pain ratings than viewing an unfamiliar dog, a plant, or a chair. Method Participants Participants for this study included 28 individuals, solicited through flyers at 2 local veterinary offices, and through word of mouth. Volunteers over the age of 18, who had lived with the same dog for at least a year, were invited to participate in this study with their dog. Participants for this study included 28 individuals (13 females and 15 males) between the ages of 19 and 63 years old ( M =30.79, SD =15.91 Mdn =22.50). The flyers explicitly stated that participants would be separated from their dog for a period of about 20 minutes and that they could bring a trusted individual, with whom the dog feels comfortable, to accompany the dog during this period.
39 Materia ls Demographic questionnaire. Participants were asked to answer questions regarding demographic information. This included information on participant age, participant gender, and the breed of all dogs currently residing with the participant (See Appendix A for full survey). Measure of Attachment Features. Kurdek's (2008) measure of attachment features is a scale in which participants are asked how strongly they agreed with 16 statements on a scale from 1 (strongly disagree) to 7 (strongly agree). Of the 16 items on the scale, four were related to safe haven (e.g., "When I am feeling bad and need a boost, I turn to my dog to help me feel better"), four were related to secure base (e.g., "I can count on my dog to be there for me"), four related to proximity maintenance (e.g., It is important that I see my dog regularly "), four were related to separation distress (e.g., "I miss my dog when I am away from him or her") and five were related to general attachment (e.g., "My dog holds a special place in my heart ") (see Appendix B for the full survey). Scores on each question were summed such that final scores ranged from 21 to 147, with higher scores representative of stronger attachment. Kurdek (2008) found strong internal consistency with Cronbach alpha ratings of .97 for safe haven, .91 for secure base, .97 for proximity maintenance and .94 for separation distress. Visual Analog Pain Scale 11. An 11 point visual analog pain scale (VAS 11) was used to determine participants' level of discomfort. The scale rang ed from 0 no pain to 10 worst pain imaginable with a mid point of 5 moderate discomfort (see Appendix C for pain scale).
40 Instruments Cold Pressor Task. A Cold Pressor Kit was constructed using a cooler, a metal grate, and a General AQ150 Waterproof Digita l Aquarium Thermometer. The apparatus was divided into two sides, separated by the metal grate. One side contained free water while the other side contained mostly ice. This was to insure that participants would not come in direct contact with the ice. The ice water was maintained between 4C and 7C (see Figure 1). Physiological measures. Systolic blood pressure, diastolic blood pressure and heart rate were measured using a LifeSource UA 767PV digital blood pressure monitor Slide shows. Four slide shows were created as a manipulation of the independent variable. Each slide show consisted of 5 images of an object (participant's own dog, unfamiliar dog, plant, or chair), taken from standardized angles (see Appendix D for photos). During the slide shows, th e photos were presented in a randomized order, appearing for 10 seconds each using the Ken Burns effect as the transition style. Each slide show lasted for 5.5 min. Slide shows were presented to each participant on a computer screen using the application i Movie. The screen was positioned approximately 100 cm from participants' eye level. Procedure Session 1. Participants were randomly assigned to one of three conditions: Familiar pet, unfamiliar pet, and plant. Each participant arrived at the experimental setting with his or her dog and if they desired, a trusted companion to accompany the dog during the times it would be separated from the owner. Upon arrival to the experimental setting, the owner
41 dropped off the dog with a research assistant, before going to the testing setting. The trusted companion was permitted to go with the dog to reassure both the dog and the owner. The dog was brought to a sequestered room, where the participants couldn't see or hear the dog. The dogs of participants in the familiar dog condition were photographed from five standard angles. Dogs of participants in other conditions were allowed to relax for a period of about 20 25 min. When participants arrived at the testing setting they were attached to the LifeSource UA 767PV digi tal blood pressure monitor and were instructed to relax for 10 min. Following this 10 min period, baseline measures of BP and HR were collected every minute for a 3 min period. The resultant 3 readings of each measure were averaged to obtain baseline measu res of HR and BP. Participants were then read the following directions: In a moment you will be shown a 5 minute 30 second slide show. After 30 seconds, when I signal, you will be asked to place your non dominant hand, palm facing down, in the water, on th is side of the divider (gesture to the ice free side of the divider) until the water reaches one inch above your wrist. Do not rest your hand on the bottom or sides of the container. When your hand is completely in the water (1 inch above wrist) say the wo rd Ready' I would like you to keep your hand in the water until it becomes uncomfortable (beyond moderate discomfort) or until 5 minutes have elapsed. In the event that your pain goes beyond moderate discomfort you may remove your hand at any point and say the word Stop'.
42 You will be asked to rate the pain on a 11 point scale every 20 seconds. I will say the words Pain rating' every 20 seconds to indicate that you should call out a number corresponding to a 11 point pain scale ranging from 0 (no pain ) to 10 (worst pain imaginable)." The slide show containing photographs of a chair was presented for 30 seconds before participants were signaled to submerge their hand in the ice water. During the Cold Pressor Task, diastolic blood pressure, systolic bl ood pressure, and heart rate were stored in the monitor every minute until the participant terminated the task (when pain level reached moderate discomfort on the pain scale), or until 5 minutes had elapsed. Participants rated their level of pain on the VA S 11 every 20 seconds. Measures of pain included both the numerical designations assigned by the participant and the time that each participant's hand remained submerged in the ice water. Following completion of the Cold Pressor Task each participant was a sked to complete a survey packet containing a measure of attachment features and demographic information. Participants were then reunited with their dogs and were thanked, and compensated with a $5 Starbucks gift card. Before leaving the experimental setti ng a follow up appointment was scheduled for the second session of the experiment. Follow up appointments were made for 1 3 weeks after the initial session. Session 2 Each participant arrived at the experimental setting alone. Upon arrival, each particip ant was, again, attached to a heart rate and blood pressure monitor and were instructed to relax for 10 minutes. Following this 10 minute period, baseline measures of BP
43 and HR were collected every minute for a 3 minute period. The resultant 3 readings of each measure were averaged to obtain baseline measures of HR and BP. A Slide show featuring the participant's own dog, an unfamiliar dog, or a plant was presented to each participant for 30 seconds, before they were asked to submerge their hand in the cold water to begin the Cold Pressor Task. The Cold Pressor Task protocol was identical to that of the first session with the only difference being the content of the slide show. During the Cold Pressor Task, diastolic blood pressure, systolic blood pressure, heart rate, and pain ratings were collected every minute, and pain ratings were collected every 20s. At the end of this session, participants were thanked, debriefed, and compensated with a $5 Starbucks gift card and a dog toy. Results Attachment Attachm ent was defined as participants' attachment bond to their pets, as measured by Kurdek (2009), which included questions relating to safe haven, secure base, proximity maintenance, separation distress, and general attachment. The minimum attachment score, in dicating low attachment, was 21, the maximum attachment score, indicating high attachment, was 147. Overall, participants were highly attached to their pets ( M =123.41, SD =21.19). Furthermore, there was no significant difference in attachment between the co nditions (see Figure 2 for means) F (2, 25)=1.80, p =.1868. This indicates that any differences between conditions cannot be attributed to level of attachment. Pain Tolerance The first analyses were on the dependant variable of pain tolerance. This variabl e
44 described the amount of time that each participant kept his/her hand submerged in the cold water. This time was the point at which the participant reported his/her pain as a 5 on the VAS 11. In the event that the participant's pain level never reached a 5 on the VAS 11, the experimenter terminated the task after 5 minutes, and that participant's time score was recorded as 5 minutes. Thus time described the level of pain such that a lower time was associated with higher pain ratings and a higher time was a ssociated with lower pain ratings. This variable of time was compared over the chair session and the experimental session. During the chair session all participants were shown a slide show of a chair. During the experimental session participants were shown a different slide show depending on their condition (familiar dog, unfamiliar dog, and plant). Pain tolerance was examined using a 3(Condition: familiar dog, unfamiliar dog, plant) x 2(Session: chair, experimental) mixed ANOVA with repeated measures on se ssion (see Figure 3 for means). There was no main effect of condition on pain tolerance such that there was no significant difference in between participants in the familiar dog condition ( M =137.15, SD =96.94), the unfamiliar dog condition ( M =133.11, SD =12 7.38), and the plant condition ( M =139.5, SD =96.58), F (2, 25)=.01, p =.9925. There was a main effect of session such that participants kept their hands in the ice bath longer during the experimental session, indicating higher pain tolerance, ( M =145.00, SD =10 7.76) than they did during the chair session ( M =115.036, SD =107.28) F (1, 25)=17.17, p =.0003. Furthermore, there was a significant interaction between condition and session on time, F (2, 25)=3.39, p =.0498. Related samples t tests were performed to compare the time during the chair session and the time during the experimental, for each condition (see Figure 3 for means). The first
45 related samples t test compared the difference in time between the chair session and the experimental session for participants in the familiar dog condition. Participants had a higher pain tolerance, when they were viewing photos of their own dog, than they did when they were viewing photos of a chair, t (9)= 3.43, p =.0075. There was no difference in pain ratings when participants we re viewing an unfamiliar dog and a chair, t (8)= 1.19, p =.2691. Those in the plant condition kept their hand in the ice water significantly longer when they were viewing the plant slide show than when they were viewing the chair slide show, t (8)= 2.61, p =.0 312. An additional variable called difference in time was created so that the difference in time between the chair session and the experimental session could be compared across all three groups directly. This variable was created by subtracting each parti cipant's time during the chair session from his/her time during the experimental session. Thus, a positive score is indicative of a longer time on the experimental session, while a negative score is indicative of a longer time on the chair session. This al lowed each participant's time on the chair session to serve as his or her own baseline. Levene's test for homogeneity of variance suggested that the data were not normally distributed F (2,25)=9.04, p =.0011, indicating that a non parametric test should be u sed. A nonparametric 1 way ANOVA using a Kruskal Wallis test revealed near significant differences between the means of the three conditions on their difference in time between the chair session and the experimental session, (2) = 5.76, p =.0561. A Mann W hitney U post hoc test was conducted to determine which conditions differed from one another in their time difference between the two sessions. This test
46 revealed that those in the familiar dog condition had a significantly larger difference in time betwee n their performance in the chair session and their performance in the experimental session than those in the unfamiliar dog condition, (1)=6.9228, p =.0085. There was no significant difference between the plant condition and the familiar dog condition on the difference in time between the experimental trial and the chair trial, (1) = .0000, p =1.00. There was no significant difference b etween the plant condition and the unfamiliar dog condition on the difference between their time scores on the chair session and the experimental session, (1) = .1334, p =.1334. Baseline Physiological Measures Before participants were exposed to the cold water, baseline measures of systolic blood pressure, diastolic blood pressure, and heart rate were collected once every minute for 3 minutes. These three readings of systolic blood pressure, diastolic blood pressure, and heart rate were averaged to obtain baseline measures of each measure. Systolic Blood Pressure. Baseline systolic blood pressure on the chair session, was examined using a 3(Condition: familiar dog, unfamiliar dog, plant) x 2 (Session: chair, experimental) mixed ANOVA with repeated measure s on session (see Figure 4 for means). There was no significant difference in baseline systolic blood pressure between participants in the familiar dog condition ( M =108.52, SD =13.62), the unfamiliar dog condition ( M =107.65, SD =6.82), and the plant conditio n ( M =114.59, SD =8.64), F (2,25)=1.52, p =.2393. In addition, there was no significant main effect of session on baseline systolic blood pressure, such that there was no significant difference between the chair session ( M =109.83, SD =10.41) and the experimenta l session ( M =110.55, SD =10.13), F (1,25)=.18,
47 p =.6728. Furthermore, there was no interaction between session and condition on baseline systolic blood pressure, F (2,25)=.56, p =.5756. Diastolic Blood Pressure. Baseline diastolic blood pressure was examined u sing a 3(Condition: familiar dog, unfamiliar dog, plant x Session: chair, experimental) mixed ANOVA with repeated measures on session (see Figure 5 for means). There was no significant main effect of condition on baseline diastolic blood pressure, such tha t there was no significant difference between the familiar dog condition ( M =69.08 SD =8.47), the unfamiliar dog condition ( M =67.19, SD =7.79), and the plant condition ( M =72.54, SD =6.86) F (2,25)=1.37, p =.2717. In addition, there was no significant main effec t of session on baseline diastolic blood pressure, such that there was no significant difference between the chair session ( M =109.83, SD =10.41) and the experimental session ( M =110.55, SD =10.13) F (1,25)=1.11, p =.3013. Furthermore, there was no significant interaction between session and condition on baseline diastolic blood pressure, F (2,25)=1.33, p =.2822. Heart rate. Baseline heart rate was examined using a 3(Condition: familiar dog, unfamiliar dog, plant x Session: chair, experimental) mixed ANOVA with r epeated measures on session (see Figure 6 for means). There was no significant main effect of condition on baseline heart rate over both sessions, such that heart rate did not differ between the familiar dog condition ( M =81.57, SD =12.39), the unfamiliar do g condition ( M =79.20, SD =13.09), and the plant condition ( M =78.50, SD =8.01), F (1,25)=.50, p =.4854. In addition, there was no significant effect of session on baseline heart rate, such that heart rate did not differ between chair session ( M =79.02, SD =10.08) and the experimental session ( M =80.62, SD =12.64), F (2,25)=.26, p =.7726. Furthermore, there was no interaction
48 between session and condition on baseline heart rate, F (2,25)=.30, p =.7415. When taken together, these analyses suggest that there were no signi ficant effects of session or condition on baseline measures of systolic blood pressure, diastolic blood pressure, or heart rate. Thus any effects of blood pressure and heart rate cannot be attributed to any differences that existed during the baseline peri od. Physiological Measures During the Cold Pressor Task Systolic Blood Pressure. Analyses were conducted on the variable of peak systolic blood pressure. This variable described the systolic blood pressure during the increment in time just before each par ticipant removed his/her hand from the cold water (when participants reported their pain as a 5 on the VAS 11). Participants whose pain did not reach a 5 on the VAS 11 were excluded from these analyses (N=7). Peak systolic blood pressure was examined using a 3(Condition: familiar dog, unfamiliar dog, plant) x 2 (Session: chair, experimental) mixed ANOVA with repeated measures on session (see Figure 7 for means). There was no significant main effect of condition on their systolic blood pressure over both tr ials, such that systolic blood pressure did not differ between the familiar dog condition ( M =127.57, SD =15.90), the unfamiliar dog condition ( M =114.50, SD =11.22), and the plant condition ( M =135.07, SD =30.51), F (2, 17)=1.94, p =.1743. There was no significan t main effect of session such that peak systolic blood pressure did not differ between the chair trial ( M =122.00, SD =13.60) and the experimental trial ( M =130.55, SD =26.91), F (1, 17)=3.76, p =.0694. There was no significant interaction between condition and session on peak systolic blood pressure, F (2, 17)=2.37, p =.1236. Diastolic Blood Pressure. Analyses were conducted on the variable of peak
49 diastolic blood pressure. This variable described the diastolic blood pressure during the increment in time just bef ore each participant removed his/her hand from the cold water (when participants reported their pain as a 5 on the VAS 11). Participants whose pain did not reach a 5 on the VAS 11 were excluded from these analyses. Peak diastolic blood pressure was examine d using a 3(Condition: familiar dog, unfamiliar dog, plant) x 2 (Session: chair, experimental) mixed ANOVA with repeated measures on session (see Figure 8 for means). There was no significant main effect between conditions on their peak diastolic blood pr essure, such that diastolic blood pressure did not differ between the familiar dog condition ( M =81.00, SD =12.38), the unfamiliar dog condition ( M =76.25, SD =12.94), and the plant condition ( M =85.71, SD =9.22), F (2, 17)=1.21, p =.3235. There was no significant difference in peak diastolic blood pressure between the chair session and the experimental session, such that peak diastolic blood pressure during the chair session ( M =80.80, SD =10.86) did not differ from peak diastolic blood pressure during the experimen tal session ( M =81.65, SD =12.19 ), F (1, 17)=.27, p =.6078. There was no significant interaction between condition and session on peak systolic blood pressure, F (2, 17)=3.01, p =.0759. Heart rate. Analyses were conducted on the variable of peak heart rate. This variable described the heart rate during the increment in time just before each participant removed his/her hand from the cold water (when participants reported their pain as a 5 on the VAS 11). Participants whose pain did not reach a 5 on the VAS 11 were excluded from these analyses. Peak heart rate was examined using a 3(Condition: familiar dog, unfamiliar dog, plant) x 2 (Session: chair, experimental) mixed ANOVA with repeated measures on
50 session (see Figure 9 for means). There was no main effect of co ndition, on their peak heart rate, such that there was no significant difference between participants in t he familiar dog condition ( M =80.21, SD =7.54), the unfamiliar dog condition ( M =82.42, SD =11.39), and the plant condition ( M =84.64, SD =9.12), F (2, 17)=. 62, p =.5476. There was no main effect of peak heart rate such that there was no significant difference between the chair session ( M =82.30, SD =8.02) and the experimental session ( M =82.55, SD =10.53), F (1, 17)=.01, p =.9231. There was no significant interactio n between condition and session on peak heart rate, F (2, 17)=2.27, p =.1332. Discussion Pain Tolerance As illustrated by the results, there was a significant difference in participants' tolerance of pain (as measured by the amount of time that each particip ant kept his/her hand in cold water). Specifically, there was a significant difference between participants' time on the chair trial and their time on the experimental trial, such that participants in the plant group and the familiar dog condition had sign ificantly longer times during their experimental session than during their chair session, however this was not observed with exposure to an unfamiliar dog. This is indicative of lower pain ratings during the familiar dog session and the plant session than in the chair session, suggesting that, exposure to both a plant and a familiar dog increase pain tolerance in comparison to a neutral stimulus (chair), while exposure to an unfamiliar dog has no such effect. The finding that exposure to photos of a familia r dog in comparison to a chair can increase time before pain reached a
51 level of 5 is consistent with studies of human attachment, which have found that photos of an attachment figure in comparison to photos of a chair can significantly reduce subjective pa in experienced (Master et al., 2009). A similar effect was observed for participants in the plant condition. Participants in the plant condition had significantly longer time scores during the experimental session than they did during the chair session. Th is is consistent with prior studies on the restorative effects associated with exposure to nature and natural landscapes ( Ulrich, 1999; Diette et al., 2003; Valchanov & Ellard, 2010 ). For example, Diette et al. (2003) found that physiological reactions ass ociated with pain were significantly reduced with exposure to virtual natural stimuli (an audio file of nature sounds, and a photo of a natural landscape). In contrast to the familiar dog and plant conditions, there was no significant difference in time be tween the chair session and the experimental session for those in the unfamiliar dog condition, suggesting that exposure to the photos of the unfamiliar dog had no effect on pain. One possible reason for this is that the photo prompts of the unfamiliar dog was not sufficient to elicit the pain reduction that has been observed during exposure to live unfamiliar dogs (Hansen et al., 1999; Havener et al., 2001; Braun, 2009). Though previous research has found that exposure to photographs of a significant other had a slightly stronger effect than did hand holding, it is important to take into consideration that when participants were holding an object (their partner's hand, a stranger's hand or an object), they were not given any visual stimulus (Master et al., 2009). Thus, the handholding condition cannot be considered a full fledged live interaction, as it only involved tactile interaction. This would suggest that the plant and the familiar dog have such strong effects, that they are able to overpower the limit s associated with the use of
52 photographs as prompts. The lack of significant findings with the use of photographs of unfamiliar dogs is not particularly surprising, given that all of the studies that have found a reduction in pain with exposure to unfamili ar companion animals have involved exposure to live dogs (Hansen, et al., 1999; Havener et al., 2001; Braun, 2009). Unfortunately, no such studies have examined the effects of exposure to unfamiliar dogs though the use photographs, making it difficult to d raw comparisons. There was a significant interaction between condition and session, in which those in the familiar dog condition had significantly longer times in the experimental session than the chair session in comparison to those in the unfamiliar dog condition. This is consistent with studies of human attachment, which have found that exposure to photographs of an attachment figure can reduce pain significantly more than viewing photographs of a stranger (Master et al, 2009). This suggests that dogs h ave the ability to function as attachment figures. Further, there was no significant difference between the plant condition and the unfamiliar dog condition on the difference between their times on the experimental trial and their time on the chair trial, though there was a trend towards a greater pain reduction in the plant condition than in the unfamiliar dog condition. Finally, there was no significant difference between the familiar dog condition and the plant condition on times in the experimental tria l and in the chair trial, supporting the idea that a familiar dog and a plant have a comparable ability to reduce pain. However, there was a significant difference between the difference in time between the chair trial and the experimental trail for partic ipants in the familiar dog condition and the unfamiliar dog condition. One possibility is that the Biophilia effect requires attachment to be activated for non human animals.
53 However, this interpretation is suspect given that the two dogs (i.e., familiar a nd unfamiliar) are more similar than a dog and a plant. A more likely explanation is that the reduction in pain associated with exposure to the familiar dog was a result of the attachment bond. This is consistent with human studies of attachment which have found that exposure to an attachment figure can reduce experimentally induced pain (Master et al., 2009; Eisenberger et al., 2011). Furthermore, this attachment to one particular dog does not appear carry over to all dogs. This interpretation would sugge st that the effects of exposure to the plant were a result of the Biophilia effect, and that the properties of plants do not carry over to encompass all living things. Thus, the effects of Biophilia, that are associated with the plant do not carry over t o include the unfamiliar dog or the familiar dog, and the effects of attachment that are associated with the familiar dog, do not carry over to encompass all dogs in general. Physiologic Measures The results illustrated that there was no significant diffe rence between the conditions or the sessions on systolic blood pressure, diastolic blood pressure or heart rate. As mentioned previously, peak physiologic measures (systolic blood pressure, diastolic blood pressure, and heart rate) were defined as that par ticular measure during the increment in time just before participants withdrew their hands from the cold water The fact that there were no significant differences in physiological measures is not particularly surprising, given that previous research has y ielded mixed results, even when using live companion animals. The use of live companion animals appears to have a stronger effect than the photographs that were employed in the current study. This is based on the current study's
54 failure to replicate previo us findings of reduced pain in participants who were exposed to unfamiliar dogs (Hansen et al., 1999; Havener et al., 2001; Braun, 2009). Braun (2009) found that when participants were in pain, there was no significant effect of exposure to live companion animals on heart rate or blood pressure. The studies that have found significant effects of unfamiliar companion animals on heart rate and blood pressure involved interaction with a live unfamiliar companion animal (Friedmann, 1983; DeMello, 1999) rather t han the mere presentation of photographs. No study to date has compared the effects of exposure to photographs of companion animals in comparison to live interaction with a companion animal. Thus, it is not particularly surprising that the photographs of c ompanion animals did not have a significant effect on blood pressure or heart rate. Studies on human social support and pain have successfully used photo prompts with the effect slightly stronger than tactile interaction (hand holding). However the fact th at the reduction in pain was comparable to tactile interaction does not speak to the effects that are associated with true interaction, which may involve both tactile and visual stimuli. There are two possible explanations for the finding of no significan t effect of photos of familiar dogs on physiological readings. The first possibility is that the use of photographs was not sufficient to trigger the physiological reactions we have in proximity to live companion animals. The current study found that prese ntation of photographs of an unfamiliar dog was not sufficient to replicate findings of reduced pain (Hansen et al., 1999; Havener et al., 2001; Braun, 2009) and blood pressure (Friedmann, 1983; Baun, 1984; DeMello, 1999). This suggests that photo prompts were simply not a strong enough manipulation to allow the full effect to be observed. However this makes the significant
55 findings of pain tolerance all the more telling. It remains possible that there was an interaction with time such that there was an in itial increase in blood pressure followed by a gradual decline. Baun et al. (1984) found that proximity to a familiar dog results in a slight initial rise in blood pressure and heart rate for 3 minutes, followed by a gradual decrease in blood pressure, whi le exposure to an unfamiliar dog did not result in such an interaction. Because the current study was terminated after 5 minutes, and the majority of participants terminated the task before 3 minutes had elapsed it is possible that participants may not hav e been exposed to the familiar dogs for long enough to receive the relaxation effect, or that no pattern was found because the elevation initial in blood pressure masked the subsequent depression of blood pressure. The non significant effect of viewing ph otos of a plant on physiological readings did not confirm the hypothesis that exposure to a plant would reduce physiological arousal. However this does make logical sense because studies that have found a significant effect of exposure to natural landscape s on physiological readings employed the use of motion videos of dynamic natural landscapes with numerous elements, such as plants, rocks, and water (Ulrich, 1999). However, it is important to note that Ulrich (1999) examined the effects of nature exposure on physiological recovery time following a stressful task, rather than looking at peak physiological arousal during a stressful task (experimentally induced pain). Overall, it appears that exposure to a familiar dog has a strong effect on pain tolerance, increasing pain tolerance significantly more than exposure to a neutral stimulus and an unfamiliar dog. This was found despite the use of photographs, instead of the
56 presence of a live dog. Photos, however, were not able to replicate the findings of lower physiological measures in experiments that involve exposure to live unfamiliar companion animals (Friedmann, 1983; DeMello, 1999). This suggests that the photographs were not capable of capturing the full spectrum of effects that have been observed with l ive animals. Limitations and Recommendations for Future Research The current study was limited in that it was time constrained. Future replications should examine the effects of a familiar dog, and unfamiliar dog and a plant on pain and physiological aro usal during prolonged periods of pain (pain lasting longer than 5 minutes). This may result in physiological differences between groups by allowing participants to adjust to the situation. Baun et al, (1984) found that exposure to one's own dog resulted in an elevation in physiological readings followed by a reduction in physiological readings after 3 minutes. Thus, expanding the time period over which people's reactions to pain were observed will allow for an examination of the effect when it is at its str ongest. This could be accomplished by looking at patients at an acute care center, who have pain to begin with rather than dealing with the ethical considerations associated with inducing pain. In situations were pain is not experimentally induced it would be possible to examine the effects of familiar dogs, unfamiliar dogs and plants on responses to pain over a longer time period. The non significant effect of the photos of the unfamiliar dog is not consistent with previous research which examined the eff ect of live unfamiliar companion animals on pain ratings (Hansen, et al., 1999; Havener et al., 2001; Braun, 2009) and physiological measures (Friedmann 1983; Baun 1984; DeMello, 1999). It may be necessary to adjust the current
57 study's method, to include l ive exposure to companion animals and natural landscapes to further explain the effects of familiar dogs, unfamiliar dogs, and plants. Specifically, past researchers' findings have illustrated that proximity to unfamiliar dogs reduced phsysiological measur es such as systolic blood pressure, diastolic blood pressure, and heart rate, as well as pain ratings. Because all of these studies used physical proximity to a live dog, it is probable that photographs did not yield a strong enough effect the physiologica l measures employed in the current study. Therefore, a future replication of this study should employ exposure to live stimuli in addition to photographs. Additionally, it would be interesting to add an additional variable of live presentation and photogra phs of a significant other. This would indicate whether attachment to dogs and attachment to people have comparable effects on pain. The effects associated with the familiar dog may be similar to those associated with a significant human other, due to the common thread of attachment. However, Allen et al. (2002) found that when faced with stress people demonstrate the highest physiological reactivity when in the presence of their spouse, and the lowest physiological reactivity when in the presence of a pet. Thus, the familiar pet may reduce pain to a greater extent than the significant other. Furthermore, the current experiment was constrained by technology. While the cold pressor task has been employed in multiple studies, with reasonable results, it is li mited in many regards. The temperature can maintained within a few degrees, however this slight variance in temperature makes finding significance all the more challenging. Additionally, this task is not ideal for repeated measures because it typically req uires a period of 2 weeks before the task can be repeated with accurate results (Allen et al., 1991). Employing the use
58 of a thermode to measure pain tolerance and induce pain would improve the current design of the study by allowing for greater precision and by allowing for several repeated blocks of trials in succession (Master et al., 2009; Eisenberger et al., 2011). This would allow for more repeated measures such that pain could be assessed as each participant viewed a live familiar dog, photos of a fa miliar dog, a live unfamiliar dog, photos of an unfamiliar dog, a neutral object (chair), photos of a neutral object (chair), a significant other, and photos of a significant other. The current study employed a 3(Conditon: familiar dog, unfamiliar dog) x 2(Session: chair, experimental) design, under the assumption that there was no difference between the sessions other than the protocol. However, during the experimental trial, participants had already run through the protocol during the chair session, whic h may have had an effect on their performance. Future replications should include an additional condition of chair to ensure that there was no effect of repeating the task. This problem could also be solved by having one session and 4 treatment groups, how ever because participants are so variable in their pain tolerance, this would require a much larger sample size. Implications The current study's findings have very strong implications for the use of familiar companion animals as a pain intervention in c linical settings. Previous research has found that interaction with an unfamiliar companion animal can significantly reduce pain (Friedmann, 1983; Baun, 2009). However the current study suggests that a familiar dog is more effective in reducing subjective pain experienced by participants than an unfamiliar dog. This may suggest that a familiar dog may be more effective in animal assisted
59 interventions than an unfamiliar dog, due to the strong role of attachment in pain reduction (Master et al., 2009). Alth ough further research is warranted to compare directly the effects of photos with those of live stimuli, it appears that photos of plants and pet dogs are sufficient to reduce subjective accounts of pain. This may suggest that presentation of photos of pla nts and pets may be employed as a cost effective, sterile animal assisted intervention. Furthermore, the current findings suggest that plants may be used as a substitute for a pet for people who, for whatever reason (allergies, fear, immobilization), may n ot be able to own a pet. Many critics of animal assisted interventions cite that exposure to animals may be a health risk to vulnerable populations in hospitals (Heady, 1999). The use of photographs as an intervention will reduce risk while still maintaini ng the pain attenuating properties that have been found to be associated with exposure to photos of plants and pets. The current study illustrated that viewing photos of a familiar dog and a plant reduces subjective pain in comparison to a chair, but view ing photos of an unfamiliar dog does not. This suggests that there is no carry over effect of attachment, such that the benefits associated with attachment do not generalize to include all dogs. Furthermore, there was no carry over effect of Biophilia in that the relaxing properties of the plant did not generalize to include all living things (the unfamiliar dog). This suggests that the relaxation effect is associated with a specific category of nature in that it appears to apply to plants but not to all a nimals.
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70 Figure 1. Experimental Set Up
71 Figure 2. Mean level of attachment by condition. p =.1868
72 Figure 3. Mean times before participants reported their pain as a 5 on the VAS 11 during the chair session and the experimental session.
73 Figure 4. Mean baseline systolic blood pressure (systolic blood pressure before pain was induced) during the chair session and the experimental session.
74 Figure 5. Mea n baseline diastolic blood pressure (diastolic blood pressure before pain was induced) during the chair session and the experimental session.
75 Figure 6. Mean baseline heart rate (heart rate before pain was induced) during the chair session and the exp erimental session.
76 Figure 7. Mean peak systolic blood pressure (Systolic blood pressure when pain was reported as a 5 on the VAS 11) during the chair session and the experimental session.
77 Figure 8. Mean peak diastolic blood pressure (diastolic b lood pressure when pain was reported as a 5 on the VAS 11) during the chair session and the experimental session.
78 Figure 9. Mean peak heart rate (heart rate when pain was reported as a 5 on the VAS 11) during the chair session and the experimental se ssion.
79 Appendix A Please answer the following questions to the best of your ability. Your responses will be kept anonymous. Do not write your name anywhere on this survey Demographic questionnaire Please answer the following questions about yourself Gender _______________ Age ____________ Please answer the following questions about the dog that you brought with you today. Breed of dog_______________________________________ Please answer the following question about any other dog with whom you cur rently share a residence. Breed(s) of other dog(s) in the home _____________________________________________________
80 Appendix B Please indicate to what degree you agree with the following statements by circling the number that best describes your relati onship with your dog. If you have more than one dog, describe the relationship with the dog you brought today. 1. I can count on my dog to be there for me. 1 2 3 4 5 6 7 Strongly agree Neutral Strongly disagree 2. I miss my dog whe n I am away from him or her. 1 2 3 4 5 6 7 Strongly agree Neutral Strongly disagree 3. I feel close to my dog. 1 2 3 4 5 6 7 Strongly agree Neutral Strongly disagree 4. When I am feeling bad and need a boost, I turn to my dog to help me feel better. 1 2 3 4 5 6 7 Strongly agree Neutral Strongly disagree
81 5. It is important that I see my dog regularly. 1 2 3 4 5 6 7 Strongly agree Neutral Strongly disagree 6. I have a n emotional tie to my dog. 1 2 3 4 5 6 7 Strongly agree Neutral Strongly disagree 7. I can depend on my dog to care about me no matter what. 1 2 3 4 5 6 7 Strongly agree Neutral Strongly disagree 8. I don't lik e to be away from my dog for extended periods of time. 1 2 3 4 5 6 7 Strongly agree Neutral Strongly disagree 9. When I am disappointed, I turn to my dog to help me feel better. 1 2 3 4 5 6 7 Strongly agree Neutral Strongly disagree
82 10. I like having regular contact with my dog. 1 2 3 4 5 6 7 Strongly agree Neutral Strongly disagree 11. I can count on my dog's trustworthiness. 1 2 3 4 5 6 7 Strongly agree Neutral St rongly disagree 12. I feel attached to my dog. 1 2 3 4 5 6 7 Strongly agree Neutral Strongly disagree 13. If I am away from my dog, I think about him or her. 1 2 3 4 5 6 7 Strongly agree Neutral Strongly disagr ee 14. When something bad happens to me, I turn to my dog to help me feel better. 1 2 3 4 5 6 7 Strongly agree Neutral Strongly disagree
83 15. I like having my dog near me. 1 2 3 4 5 6 7 Strongly agree Neutral Strongly disagree 16. I can count on my dog for comfort. 1 2 3 4 5 6 7 Strongly agree Neutral Strongly disagree 17. I have a special bond with my dog. 1 2 3 4 5 6 7 Strongly agree Neutral Strongly disagree 18. I would be upset if I had to be away from my dog for a long while. 1 2 3 4 5 6 7 Strongly agree Neutral Strongly disagree 19. When I am upset, I turn to my dog to help me feel better. 1 2 3 4 5 6 7 Strongly agree Neutral Strongly disagree
84 20. I like when my dog is with me. 1 2 3 4 5 6 7 Strongly agree Neutral Strongly disagree 21. My dog holds a special place in my heart. 1 2 3 4 5 6 7 Strongly agree Neutral Strongly dis agree
85 Appendix C
86 Appendix D Chair
87 Familiar Dog
88 Unfamiliar Dog