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.
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
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;
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
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
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.
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
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
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.
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= 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
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
Somerville, Kruglikova, Robertson, Hanson, & MacLin PETS
period, and one at the end. A 5-minute interval separated each of these
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
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,
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.
T1 T2 T3 T4 T5
M e a n M ea su re m en t
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
Somerville, Kruglikova, Robertson, Hanson, & MacLin PETS
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
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.
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
Somerville, Kruglikova, Robertson, Hanson, & MacLin PETS
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
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,
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