1 Physiological Responses by College Students to a Dog and a Cat: Implications for Pet Therapy John W. Somervill, Yana A. Kruglikova, Renee L. Robertson, Leta M. Hanson, Otto H. MacLin University of Northern Iowa The effects of physical contact with a dog and a cat on blood pressure and pulse among male and female college students were examined. The final sample consisted of 62 participants (28 males and 34 females). It was tentatively hypothesized that participants would show a reduction in blood pressure while handling both a dog and a cat. It was also speculated that male and female participants would react differently to a dog versus a cat. There were no significant blood pressure or pulse differences in response to a dog vs. a cat, nor were there significant gender differences although females generally had a lower blood pressure than males. There were no significant changes in blood pressure or pulse while participants held an animal, but a significant decrease in diastolic pressure occurred immediately following holding an animal. Results partially support previous findings of a reduction in blood pressure associated with animal contacts. Implications for pet therapy were discussed. Companion animals are an important part of our social world. We often talk to them as if they were humans and some even refer to pets as their children. They are a source of comfort, love, and their time with us is often followed by grieving when they die. The therapeutic benefits of owning a pet have been suggested by a number of studies. Cardiovascular health benefits have been found to be related to dog ownership, both in terms of length of survival (Friedmann, Katcher, Lynch, & Thomas, 1980; Friedmann & Thomas, 1995) and in general cardiovascular health (Friedmann, Thomas, Stein, & Kleiger, 2003; Serpell, 1991). An aspect of pet therapy that has not been fully explored is possible differences between species in their physiological effects on participants. Allen, Blascovitch, and Mendes (2002) found no significant differences in blood pressure and pulse rate between dog owners and cat owners. After combining dog and cat data, it was found that pet owners, as compared to non pet owners, had significantly lower resting pulse rates, Author info: Correspondence should be sent to: Dr. John Somerville, Dept. of Psychology, University of Northern Iowa, Cedar Falls, IA North American Journal of Psychology, 2008, Vol. 10, No. 3, NAJP
2 520 NORTH AMERICAN JOURNAL OF PSYCHOLOGY lower systolic and diastolic blood pressure, and exhibited significantly lower reactivity on all three measures following a stressful arithmetic task. As noted by Friedmann, Thomas, and Eddy (2000), most of the studies on short term physiological responses to an animal have used dogs, mostly because of convenience and popularity as pets. Serpell (1991) found that cat owners showed a significant short term reduction in minor health problems but not after six months. Dog owners showed a dramatic increase in the frequency and duration of walking, but cat owners showed no significant changes over a ten month period. Friedmann and Thomas (1995) found that both dog ownership and social support were positively related to one-year survival status after an acute myocardial infarction, but that cat ownership was negatively associated with one-year survival status. In addition to long term effects of pet ownership research has also focused on the effects of a relatively brief exposure to either a familiar or unfamiliar animal. The physiological effects of a brief exposure to a dog have varied according to experimental procedures, the age of participants, the types of independent variables employed, and whether a familiar or unfamiliar animal was used. Allen, Blascovich, Tomaka, and Kelsey (1991) found that participants in the presence of their own dog and the experimenter showed less physiological reactivity following a stressful arithmetic task in comparison with any other condition. Friedmann, Katcher, Thomas, Lynch, and Messent (1983), using an unfamiliar dog with 9-16 year-old children, found a reduction in blood pressure associated with a dog s presence, although results varied when the dog was introduced in the first half as opposed to the second half of the test condition. Wilson (1987), in a study of college students, assessed the effects of reading aloud, reading quietly, and petting a friendly but unfamiliar dog on measures of six dependent variables: systolic blood pressure, diastolic blood pressure, pulse rate, mean arterial pressure, Spielberger s Anxiety Questionnaire, and the Pet Attitude Inventory. Results showed that reading aloud consistently resulted in the highest increases in blood pressure while reading quietly was consistently associated with the lowest levels of blood pressure. It was concluded that interacting with the dog was more stressful than reading quietly but less stressful than reading aloud. Several studies assessed blood pressure and pulse rate changes during a condition in which participants physically interacted with a dog. Friedmann, Katcher, Meislich, and Goodman (1979) found that both systolic and diastolic blood pressure was significantly higher during a petting condition than a resting condition. However, both systolic and diastolic blood pressure were significantly higher during a reading condition than during the petting condition. Baun, Bergstrom, Langston,
3 Somerville, Kruglikova, Robertson, Hanson, & MacLin PETS 521 and Thomas (1984) found that the blood pressure and pulse rate of participants increased significantly at the beginning of the petting session, presumably because of the initial excitement associated with their dogs entering the room. The major finding was that the greatest decrease in blood pressure was among participants who petted their own dog as opposed to an unfamiliar dog. Vormbrock and Grossberg (1988) found that petting a dog without verbalization and a rest condition produced the lowest blood pressure as compared to the four other conditions studied. Minimal research has been done to assess gender differences in response to animals. Allen et al. (2002) noted that no consistent gender differences have been reported. In summary, with some exceptions, a reduction in blood pressure has been reported in most studies following limited contact with a dog. The goals of the present study were: (a) to assess the effects of limited exposure to an unfamiliar dog versus an unfamiliar cat on blood pressure and pulse rate on male and female college students, and (b) to increase physical interaction with the animals by having participants hold each animal in their lap for a five minute period. It is tentatively hypothesized that participants will show a reduction in blood pressure while handling both a dog and a cat. As noted previously, previous research has failed to support a significant difference in physiological reactions to a dog and cat. However, it was speculated that there may be gender differences in reactions to different species. METHOD The study consisted of two phases. The first consisted of a brief survey administered in a mass testing situation along with other short surveys involving unrelated studies. The second phase consisted of the primary experimental study involving physiological reactions to dogs and cats. In phase 1, participants in the mass screening were 178 students (86 males and 92 females) from introductory psychology classes who elected to participate in order to fulfill a research requirement or an acceptable alternative. Informed consents were obtained and each participant was asked to respond to a one page questionnaire entitled Cat and Dog Preference Survey consisting of demographic information, including gender, age, marital status, and ethnic origin. Participants were asked to check one of three options: (a) I like dogs, (b) I do not like dogs, and (c) I neither like nor dislike dogs. The same three options were also requested for cats.
4 522 NORTH AMERICAN JOURNAL OF PSYCHOLOGY Participants were also asked to check Yes or No if they had a dog or a cat currently living with them or their parents. Participants were excluded from further participation if they had dog or cat allergies, strong fears of dogs or cats, or problems with hypertension. Of the 178 participants in phase 1, four reported being allergic to dogs and cats, ten reported being allergic to cats, and two reported being allergic to dogs. Two persons indicated a strong fear of cats, and five persons indicated a strong fear of dogs. Two persons reported problems with high blood pressure. Only students who participated in the mass screening were eligible for phase 2. A total of 62 participants, 28 males and 34 females, signed up for and completed phase 2. The age range for males was 18 to 29 (mean= yrs.), and for females was 18 to 24 (mean= yrs.). Median age for both males and females was 19. Of the 28 males, 22 were Caucasian, four were African American, and one was Hispanic. Of the 34 females, 32 were Caucasian, one was African American, and one was other (unspecified). An informed consent for phase 2 was obtained from each participant. One of three undergraduate female research assistants took all blood pressure and pulse rate readings. The blood pressure monitor was demonstrated to each participant in advance. All blood pressure readings were taken with an automatic digital blood pressure monitor (Health-O- Meter Model 7631). During the experiment, a total of ten blood pressure and pulse readings were taken, one at the beginning and one at the end of nine 5- minute intervals. During the third and seventh 5-minute interval, each participant held either a dog or cat in their laps for the full 5 minute period. The order of presentation of a dog or cat was alternated. Measurements taken before and after the first, fifth, and ninth 5-minute interval served as baselines during which no animal was present. Between readings, casual conversation was encouraged. A second person was always in the room to ensure that the animal remained in the participant s lap during the third and seventh 5 minute time period.. The dog used for all participants was a 14 pound blond Shi-Tzu. Two cats were used, both were obtained from the local humane shelter. All animals were selected because of their gentleness, friendliness towards people, and non-aggressive behaviors. All animals were examined for parasites or fleas and had received all necessary shots. There were five phases in this experiment: (a) an initial baseline with no animal, (b) the first presentation of a dog or a cat, (c) a second baseline with no animal, (d) the second presentation of a dog or a cat, and (e) a third baseline with no animal. Two measures, blood pressure and pulse, were taken for each phase, one at the beginning of the 5 minute
5 Somerville, Kruglikova, Robertson, Hanson, & MacLin PETS 523 period, and one at the end. A 5-minute interval separated each of these ten measures. RESULTS & DISCUSSION The first procedural question was whether or not the two measures taken within each of the three baseline phases, during which no animal was present, significantly differed. No significant difference between the first and second measure for each of the three baselines was obtained. Therefore, the two measurements for each baseline were averaged. Two different cats were used during the experiment. Further analysis with t tests indicated that there were minimal differences between the first and second cat. Therefore, in subsequent analyses, data for the two cats were combined. The first question was whether blood pressure and pulse would significantly differ in reactions to a dog or cat. A related question was if there was a sequence effect depending on whether the dog was presented first or the cat was presented first. To answer both of these questions, a series of independent t tests were conducted to determine if there was a significant difference between systolic blood pressure, diastolic blood pressure and pulse rate during the following time periods: (a) holding a cat, (b) the baseline subsequent to holding a cat, (c) holding a dog, and (d) the baseline subsequent to holding a dog. Results of t tests comparing the sequence of holding a cat first vs. holding a dog second were non significant for systolic pressure, t(1,61) =.78, n.s., diastolic pressure, t(1,61) = -1.05, n.s., or pulse, t(1,61) =.71, n.s. Likewise, comparisons involving the sequence of holding a dog first vs. holding a cat second were non significant for systolic pressure, t(1,61) = 1.45, n.s., diastolic pressure, t(1,61) =.70, n.s.,or pulse, t(1,61) =.750, n.s. Consequently, the order of presentation was ignored in subsequent analyses and the data for dogs and cats were combined. No support was obtained for the hypothesis that holding a dog would result in lower blood pressure or lower pulse rate than holding a cat. Failure to find significant differences in response to a dog or cat is consistent with results obtained by Allen et al. (2002). Another procedural issue was to determine whether there were significant differences between the three baseline periods for systolic blood pressure, diastolic blood pressure and pulse. Paired sample t tests revealed significant difference between the first and third baseline for both systolic blood pressure, t (1, 61) = 3.591, p <.001, and diastolic blood pressure, t (1, 61) =2.096, p <.005; and the second and third baseline for both systolic blood pressure, t (1, 61) = 2.944, p <.005, and diastolic blood pressure, t (1, 61) = 2.008, p <.049. A significant difference was also obtained for pulse rate between the first and second baseline, t (1, 61) = 2.295, p <.025, and the first and third baseline, t (1,
6 524 NORTH AMERICAN JOURNAL OF PSYCHOLOGY 61) = 2.82, p <.006. These differences largely reflect a gradual reduction in both blood pressure and pulse rate over the course of the experimental session. Figure 1 presents the means for systolic pressure, diastolic pressure, and pulse for each of the five phases: 1) baseline, 2) holding animal, 3) baseline, 4) holding animal, and 5) baseline. Physiological Measures M ean M easu rem en t Systolic Diastolic Pulse 20 0 T1 T2 T3 T4 T5 Measurement Intervals FIGURE 1 Means for Systolic Pressure, Diastolic Pressure, and Pulse for Five Phases: 1) Baseline, 2) Holding Animal, 3) Baseline, 4) Holding Animal, and 5) Baseline. The primary hypothesis was that physical contact with an animal will lead to a decrease in blood pressure and pulse rate. Recall that the data for dogs and cats were combined. The time periods during which an animal was held in the participant s lap were compared with the time periods during which no animal was present. A separate one way analysis of variance was performed for all five time periods for systolic blood pressure, diastolic blood pressure and pulse rate. The F value for systolic blood pressure was not significant, F (4,240) =.671, p <.613, and the F value for pulse rate was not significant, F (4,240) = 2.373, p < The only significant finding was that diastolic blood pressure was lower for the baselines immediately following the animal present conditions than during the actual animal conditions, F (4,240) = 4.28, p < Multiple t
7 Somerville, Kruglikova, Robertson, Hanson, & MacLin PETS 525 tests yielded significant differences between diastolic blood pressure during first and third baselines, t (1,61)= 2.72, p <.008; the first animal condition and the second baseline, t (1,61)= 2.97, p <.004; the first animal condition and the third baseline, t (1,61)= 3.303, p <.002; and the second animal condition and the third baseline, t (1,61)= 2.293, p <.025. As indicated in Figure 1, every time the baseline followed a session with an animal, there was a small but significant decrease in diastolic blood pressure. In summary, very limited support was provided for the hypothesis that physical contact with an animal would lead to a decrease in blood pressure. The decrease was only for diastolic pressure and only occurred during the baseline periods after holding an animal. There were three other variables of interest: (1) whether the participant liked or disliked dogs or cats, (2) ownership of a dog or cat, and (3) gender of the participants. Data on dog and cat preferences and dog and cat ownership were obtained from all but one of the 62 participants. Of the 61 participants, 53 (85%) reported that they liked dogs, only 2 (3.2%) reported that they disliked dogs, and 6 (9.7%) reported that they neither liked nor disliked dogs. Cats were not as popular; 40 (64.5%) reported that they liked cats, 7 (11.3%) disliked cats, and 14 (22.6%) neither liked nor disliked cats. There were four categories of dog and cat ownership: a) owned only a dog, b) owned only a cat, c) owned both a dog and a cat, and d) owned neither a dog nor a cat. Ownership was defined as either owning an animal at their current address while in school or owning one at their home address. Of 61 participants, 19 (30.6%) reported that they owned only dogs, 11 (17.7%) owned only cats, 16 (25.8%) owned both dogs and cats, and 16 (25.8%) did not own either a dog or a cat. No significant test differences were obtained for the four ownership conditions between any of the five measurement periods for systolic blood pressure, diastolic blood pressure, or pulse rate. When the combined data for all five time periods for males and females were compared, males had slightly higher systolic blood pressure, F (1, 60) =4.494, p <.038, but this was not significant given the large number of t tests conducted. There was not a significantly higher diastolic pressure, F (1, 60) = 3.316, p <.074. Females had significantly higher pulse rate, F (1, 60) = 7.748, p <.007. There were no significant differences between males and females during the time period while an animal was held on their lap for either systolic blood pressure, F(1,60)=.226, p <.636, or diastolic blood pressure, F(1,60)= 1.491, p <.227. However, females had a significantly higher pulse rate, F (1, 60) = 6.289, p <.015.
8 526 NORTH AMERICAN JOURNAL OF PSYCHOLOGY During the time period immediately following holding an animal, females also showed significantly lower systolic blood pressure, F (1, 60) = 23.64, p <.001, but not diastolic blood pressure, F (1, 60) = 4.52, p <.038, given the large number of t tests made. During the same time period, females also had a significantly higher pulse rate, F (1, 60) = 6.911, p <.011. In summary, there were no gender differences in physiological responses while participants held an animal, but females did show a decrease in systolic blood pressure and a higher pulse rate during the time period after holding the animal. No support was found for the possibility that physiological responses to a dog would differ significantly from physiological responses to a cat. In the present study, there were no significant differences in systolic blood pressure, diastolic blood pressure or pulse between holding a cat for 5 minutes and holding a dog for 5 minutes, nor were there any significant differences in response to holding a dog or cat by male and female participants. In regard to physiological consequences, therefore, it does not appear to matter if a person is holding a cat or a dog. Since many pet therapy situations involve a similar type of limited exposure, the present study suggests that comparable results may be expected for both dogs and cats. The major hypothesis that physical contact with an animal would lead to a decrease in blood pressure and pulse was only partially supported. No significant changes occurred while an animal was being held on participants laps. However, during time periods immediately after an animal was removed, a small but significant decrease in systolic blood pressure occurred. It is possible that potential autonomic effects of holding an animal may be delayed until a brief period after the animal has been removed. In general, these results lend only minor support to the findings by others that contact with a dog or cat lowers blood pressure. However, in the present study, the fact that there was also a gradual reduction in blood pressure over time considerably weakens conclusions about effects attributable to handling a dog or cat. In designing the study it was considered possible that liking or disliking an animal might influence autonomic responses. Therefore, each participant was asked in advance of the study whether they liked, disliked, or neither liked nor disliked a cat or a dog. Results, however, indicated that few persons expressed a dislike for either cats or dogs. More people reported liking dogs than reported liking cats, a finding consistent with stereotypes about the friendliness of dogs and the aloofness of cats. Previous research has suggested that persons may have different autonomic responses to their own companion animal than to an unfamiliar animal. One also might expect that ownership of a dog or cat
9 Somerville, Kruglikova, Robertson, Hanson, & MacLin PETS 527 might influence responses to an unfamiliar dog or cat. However, there were no significant differences in autonomic responses to an unfamiliar dog or cat between dog owners, cat owners, owners of both cats and dogs, and participants who owned neither a cat nor a dog. It is tempting to speculate that in a pet therapy situation, possible therapeutic effects may be independent of previous pet ownership. In the present study, few significant gender differences were obtained. Females showed a higher increase in pulse rate than males when holding an animal. In general, females showed significantly lower systolic blood pressure than males, but had a significantly higher pulse rate. This difference, however, was unrelated to the presence or absence of an animal. In summary, the present study suggests that in the typical pet therapy paradigm one would not expect different physiological effects from the use of a dog or a cat, and relatively minimal changes in blood pressure or pulse rate while the person is interacting with an animal. The difference between long term ownership of a companion animal versus short term exposure to an animal might be compared to the difference between raising your own child versus a short term visit by someone else s child. Pet ownership, like raising a child, involves care taking and an emotional attachment that you have developed over months and years. While you may enjoy petting someone else s dog or cat, the interaction is not likely to be the same as the interaction with your own companion animal. Thus, it is not surprising that the positive, long term cardiovascular benefits associated with pet ownership affect survival and general cardiovascular health, but brief exposure to an animal may have minimal or no long term health benefits. However, even if there are only minor physiological changes, numerous anecdotal reports suggest that patients in a variety of settings enjoy interacting with companion animals. The benefits of pet therapy may be primarily related to these pleasurable experiences. An obvious limitation to the present study is that findings with college students may not be generalized to other age groups or noncollege settings selected for pet therapy such as nursing homes, hospitals, and prisons. REFERENCES Allen, K. M., Blascovich, J., & Mendes, W. B. (2002). Cardiovascular reactivity and the presence of pets, friends, and spouses: The truth about cats and dogs. Psychosomatic Medicine, 64, Allen, K. M., Blascovich, J., Tomaka, J., & Kelsey, R. M. (1991). Presence of human friends and pet dogs as moderators of autonomic responses to stress in women. Journal of Personality and Social Psychology, 61(4),
10 528 NORTH AMERICAN JOURNAL OF PSYCHOLOGY Baun, A. M., Bergstrom, N., Langston, N. F., & Thomas, L. (1984). Physiological effects of human/companion animal bonding. Nursing Research, 33(3), Friedmann, E., Katcher, A. H., Lynch, J. J., & Thomas, S. A. (1980). Animal companions and one-year survival of patients after discharge from a coronary unit. Public Health Reports, 95(4), Friedmann, E., Katcher, A. H., Meislick, D., & Goodman, M. (1979). Physiological response of people to petting their pets [Abstract]. American Zoologist, 19, 327. Friedmann, E., Katcher, A. H., Thomas, S. A., Lynch, J. J., & Messent, P. R. (1983). Social interaction and blood pressure: Influence of animal companions. Journal of Nervous and Mental Disease, 171(8), Friedmann, E., & Thomas, S. A. (1995). Pet ownership, social support, and oneyear survival after acute myocardial infarction in the Cardiac Arrhythmia Suppression Trial (CAST). American Journal of Cardiology, 76, Friedmann, E., Thomas, S. A., & Eddy, T. J. (2000). Companion animals and human health: Physical and cardiovascular influences. In A. L. Podberescek, E. S. Paul & J. A. Serpell (Ed.) Companion animals and us. Exploring the relationships between people and pets (pp ). United Kingdom: Cambridge University Press. Friedmann, E., Thomas, S. A., Stein, P. K., & Kleiger, R. E. (2003). Relation between pet ownership and heart rate variability in patients with healed myocardial infarcts. The American Journal of Cardiology, 91, Serpell, J. A. (1991). Beneficial effects of pet ownership on some aspects of human health and behavior. Journal of Royal Society of Medicine, 84, Siegel, J. M. (1990). Stressful life events and use of physician services among the elderly: The moderating role of pet ownership. Journal of Personality and Social Psychology, 58(6), Vormbrock, J. K., & Grossberg, J. M. (1988). Cardiovascular effects of humanpet dog interactions. Journal of Behavioral Medicine, 11(5), Wilson, C. (1987). Physiological responses of college students to a pet. Journal of Nervous and Mental Disease, 175(10),
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