Physiological Responses by College Students to Dogs & Cats

Author info: Correspondence should be sent to: Dr. John Somerville, Dept. of

Psychology, University of Northern Iowa, Cedar Falls, IA 50614.

North American Journal of Psychology, 2008, Vol. 10, No. 3, 519-528.

NAJP

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,

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,

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.


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= 20.04 yrs.), and for females was 18 to 24 (mean= 19.21 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


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,


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

0

20

40

60

80

100

120

140

T1 T2 T3 T4 T5

Measurement Intervals

Me

an

Me

as

ure

me

nt

Systolic

Diastolic

Pulse

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 <. 053. 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 <. 002. Multiple t


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.


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


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 non-

college settings selected for pet therapy such as nursing homes, hospitals,

and prisons.

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Physiological Responses by College Students to Dogs & Cats