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Research
Western Journal of Nursing
DOI: 10.1177/01945902024004009
2002; 24; 422 West J Nurs Res
Rebecca A. Johnson, Johannes S. J. Odendaal and Richard L. Meadows
Animal-Assisted Interventions Research: Issues and Answers
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WesternJournal ofNursing Research
June 2002, Vol. 24, No. 4
Animal-Assisted
Interventions Research:
Issues and Answers
Rebecca A. Johnson
Johannes S. J. Odendaal
Richard L. Meadows
Animal visitation programs have been used in a wide variety of clinical settings with predomi-
nantly positive outcomes reported anecdotally. However, there is also a growing body of
research investigating the effects of these interventions. Developing and conducting rigorous
studies of animal interventions can be a complex and challenging process. The purpose of this
article is to identify and discuss several issues arising with this type of research and to posit sug-
gestions for avoiding pitfalls.
Since the early 1960s, there has been a worldwide proliferation of pro-
grams in which animals visit or co-reside with human patients in hospitals,
long-term care facilities, rehabilitation facilities, public schools, and com-
munity care. Although many clinicians and authors have observed the role of
the human/animal bond in promoting health for animals and humans, it was
not until the early 1980s that efforts grew toward scientifically documenting
this phenomenon.
People who plan and implement these programs have consistently pub-
lished anecdotal evidence and testimonials regarding the benefits to partici-
pating patients and animals. Advocates of programs using animals have
begun to see empirical documentation as a critical factor in widespread
acceptance of animal-assisted activity (visitation programs) and animal-
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Western Journal of Nursing Research, 2002, 24(4), 422-440
Rebecca A. Johnson
, Ph.D., R.N., Associate Professor, Sinclair School of Nursing, Uni-
versity of Missouri–Columbia;
Johannes S. J. Odendaal
, D.V.Sc., Ph.D., Professor,
Research and Development, Life Sciences Institute, Technikon Pretoria, South Africa;
Richard L. Meadows
, D.V.M., D.A.B.V.P., Clinical Assistant Professor, College of Veteri-
nary Medicine, University of Missouri–Columbia.
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assisted therapy (programs with specific goals for individuals) as beneficial
interventions for patients. Some have emphasized that beyond merely dem-
onstrating their efficacy; outcome data may also be the first steps in estab-
lishing animal visitation programs as interventions worthy of reimburse-
ment by third-party payers. The nature of this research makes it very
important for human health care professionals and veterinarians to collabo-
rate (Johnson & Meadows, 2000a).
As is the case with many psychosocial interventions, studying the effects
of animal interventions presents particular challenges in developing and
implementing research protocols. Identifying appropriate outcome mea-
sures may be difficult, and controlling the wide array of extraneous variables
may seem insurmountable. However, investigators can design and conduct
rigorous experiments by taking into consideration the challenges that others
discover in conducting research on this topic.
The purpose of this article is to discuss several issues arising with this
type of research and to posit suggestions for avoiding pitfalls. First, the liter-
ature on physical and psychological responses to human/animal interaction
is briefly reviewed. It should be noted that primarily work using dogs is
included in the discussion because there has been far less study using other
animals. The term pet attachment is used in reference to situations in which
humans recognize a reciprocal bond or feeling of connection with a pet.
Although pet attachment may occur with pet ownership, it may also exist
without ownership. Alternatively, there may be no pet attachment with own-
ership. However, “human/pet interaction” may occur with or without pet
attachment or pet ownership.
LITERATURE REVIEW
Physiological Responses to Human/Animal Interaction
Because of a lack of understanding of many of its mechanisms, the cen-
tral nervous system (CNS) has traditionally been considered an isolated
entity in the body although mental state has been believed by many to affect
the health of the body. However, paradigm-shifting studies by Blalock and
Smith (1981) and by Livnat, Felton, Carlson, Bellinger, and Felton (1985)
demonstrated that endorphins are produced by the immune system as well as
by the CNS and that lymphocytes contain active surface receptors for
neurotransmitters. These studies, and many since them, indicate both the
anatomical and biochemical connections for a bidirectional communication
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network allowing for the physiological expression of emotions. Odendaal
(1999) took these findings further by showing that among both humans and
dogs, beneficial neurochemical changes occurred in beta endorphins, beta
phenylethylamine, prolactin, dopamine, and oxytocin after about 15 minutes
of a positive interaction.
Several investigators have demonstrated the beneficial effects of interac-
tion with animals on blood pressure of humans. For example, statistically
significant decreases in systolic and diastolic blood pressure have been
found when research participants petted a dog with which they felt a bond
(Baun, Bergstrom, Langston, & Thoma, 1984). Similar effects on blood
pressure have been reported while research participants completed mental
arithmetic tasks in the presence of their pet dogs but without physical contact
(Allen, Blascovich, Tomaka, & Kelsey, 1991). These effects have been
found to be primarily related to an individual’s perception of animals (corre-
spondingly positive or negative) (Friedmann, Locker, & Lockwood, 1993).
As with any intervention, timing is critical to its success. For example,
Friedmann, Katcher, Thomas, Lynch, and Messent (1983) found that intro-
ducing a dog at the beginning of an experiment produced a more beneficial
effect than if the dog was introduced during the middle of the experiment.
This finding suggests that introducing the dog at the beginning of stressful
experiences may help moderate the patient’s response. In fact, other investi-
gators who introduced the animal in midexperiment found no significant
responses in blood pressure or heart rate (Straatman, Hanson, Endenburg, &
Mol, 1997).
This type of blood pressure or stress reduction in response to human/
animal contact may underpin the classic finding that 1-year survival rate was
positively associated with pet ownership among patients discharged from a
coronary care unit irrespective of age (Friedmann, 1990; Friedmann,
Katcher, Lynch, & Thomas, 1980). This finding was subsequently repli-
cated in large scale (Friedmann & Thomas, 1995). Pet attachment has also
been associated with physiologic indicators of health among older adults.
For example, Anderson, Reid, and Jennings (1992) found pet ownership
associated with lower systolic blood pressure, triglyceride, and cholesterol
levels. However, Lago, Delaney, Miller, and Grill (1989) found that pet
ownership influenced health indirectly through improving morale. Pet own-
ership may be viewed at the far end of a continuum of human/pet interaction,
that is, the condition of maximal interaction and thus perhaps the most bene-
ficial level of interaction. However, in lesser interaction situations—in the
laboratory and in clinical settings via visitation programs—similar benefi-
cial responses have been reported. For example, greater relaxation response
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was reported among older adults who watched fish swimming in an aquar-
ium than among those who watched a videotape of fish swimming
(DeSchriver & Riddick, 1991), and systolic and diastolic blood pressure
decreases were demonstrated in response to a dog visitation group activity
program in nursing home residents (Neer, Dorn, & Grayson, 1987).
Psychological Responses to Human/Animal Interaction
Conversely, social stressors have been associated with negative physio-
logical responses such as immune suppression in humans and animals. For
example, premature separation of the mother-infant dyad among weaned
squirrel monkeys resulted in suppressed immune function (Coe, Lubach, &
Ershler, 1989). Similarly, anxiety and other psychosocial stresses among
laboratory animals resulted in low immunocompetence to cancer, infective
agents, and other disease processes ordinarily resisted by the body through
humoral and cellular immunity (Riley, 1981).
There is evidence documenting pets as sources of stress relief, comfort,
support, and unconditional love in a variety of age groups. For example,
Triebenbacher (1998) found that among primary school children younger
than Grade 5, the majority were very excited to see their pets when they
returned home from school and believed their pets commonly communi-
cated love to them. Among young women, the pet dog may have actually
been a substitute for human support in that those living only with a dog were
significantly more attached to the dog than those living with both a dog and
with people (Zasloff & Kidd, 1994). Among community-dwelling older
adults, pets were viewed as fun, dependent, and relaxing. Pets were viewed
like the participants’ own child irrespective of whether or not the elders had
children (Berryman, Howells, & Lloyd-Evans (1985).
Garrity, Stallones, Marx, and Johnson (1989) found that pet attachment
was related to decreased depression among older adults. Among research
participants with less social support, this finding was related to levels of
health. Bereaved elders with less social support had less depression if
attached to their pets. A similarly positive relationship was found between
pet ownership, attachment, and mental status in the elderly. Later, laboratory
investigation showed a strong relationship between pet interaction and
lower depression levels among college students as well (Folse, Minder,
Aycock, & Santana, 1994).
Among nursing home residents, visitation sessions with pets were found
to improve health self-concept, social competence and interest,
psychosocial functioning, life satisfaction, and personal neatness and mental
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function and to decrease depression (Francis, Turner, & Johnson, 1985).
Other investigators found that elderly nursing home residents in general
(Fick, 1993; Taylor, Maser, Yee, & Gonzalez, 1993; Winkler, Fairnie,
Gericevich, & Long, 1989) and those with dementia in particular (Kongable,
Buckwalter, & Stolley, 1989) increased their social interacting in response
to interactions with a dog.
Human/Animal Interaction as a Clinical Intervention
Animals have been entered into the therapeutic environment as interven-
tions in usually one of two ways. Visitation programs are the most common,
in which animals are brought to particular clinical settings for structured or
unstructured interaction. Residential programs in which an animal actually
lives permanently in a particular clinical setting have also been reported.
The most commonly studied sites for either type of animal intervention have
been long-term care settings. However, few studies have investigated
whether visitation programs are more beneficial than residential programs.
In the one study that sought to answer this question, no differences in the
social behavior of elderly residents of an Alzheimer’s Special Care Unit
were found between visitation and resident animal conditions (Kongable
et al., 1989).
Studies of residential pet programs have reported positive outcomes in
elderly residents and staff members. For example, Winkler et al. (1989)
found that both nursing staff members and elderly nursing home residents
responded to the presence of a resident dog by being more socially interac-
tive with each other. Similar findings had previously been reported by
Brickel (1979), who found that two resident cats in a long-term care hospital
ward stimulated patient interaction and appeared to be a source of comfort to
the older adults who interacted with the animals.
Pet visitation programs have been reported to be beneficial—commonly
among the long-term care population. The most commonly studied depend-
ent variable when pet visitation programs have been tested is increased
social interaction among elderly nursing home residents (Beyersdorfer &
Birkenhauer, 1990; Fick, 1993; Kongable et al., 1989; Taylor et al., 1993).
This variable is of considerable importance to this population as social isola-
tion is a major problem in the nursing home setting.
Although social interaction is of concern for nursing home residents,
there is a critical need for investigation of other variables among this popula-
tion. Given that social interaction in response to pet contact has been
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demonstrated and that older adults may be particularly responsive to this
interaction, replication of community-based studies demonstrating
increased physical activity and health and decreased depression and loneli-
ness need to be conducted in the nursing home setting. Another potentially
fruitful area of inquiry as yet unstudied among this population is the role of
prescribed pet interaction in promoting beneficial neurohormonal responses
that facilitate health. There is clearly a dearth of controlled experiments
demonstrating the effects of animal interventions on many biophysical and
psychosocial outcomes.
In addition, there is a lack of study comparing the use of different animals
in the intervention. Whereas some research has investigated effects of pres-
ence of cats (Brickel, 1979) and fish aquaria (N. Edwards, personal commu-
nication, September 29, 2001) on psychosocial and biophysical outcomes
among the elderly, little published empirical data exist. Although the Eden
Alternative nursing home model (one including pets, plants, and a “normal-
ized” environment) has been used in facilities for several years, few studies
have resulted.
Another area of inquiry in which little to no research exists is investiga-
tion into the effects of animal interventions on various other populations
such as cancer patients, children, and AIDS patients, to list a few. These pop-
ulations may present daunting challenges to the design and conduct of
research such as debilitating effects of disease treatment, logistics of where
treatment is given, fear of animals, or risk of infection, which will be dis-
cussed later in this article. However, these challenges can be met with rela-
tively uncomplicated measures if these are given adequate consideration in
developing the study.
ISSUES ASSOCIATED WITH CONDUCTING
ANIMAL INTERVENTION RESEARCH
Gaining Access to Clinical Settings
Once the overall study design is determined, and the most critical steps in
the protocol are developed for introducing and testing the animal interven-
tion, the need to gain access to an appropriate clinical site arises. Ideally, the
investigator has already begun informal dialogue with appropriate staff
members from the desired facility to introduce the study and elicit support.
However, as this is not always possible, it now becomes necessary for open
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discussions with key staff and management personnel who can help the
investigator negotiate the formal and informal channels of approval to con-
duct the study.
Some challenges to gaining access include the complexity of negotiating
corporate structures to seek approval for the project and the fact that the
desired facilities may be located in a city some distance from the investiga-
tor. Additionally, the current health care environment of buy-outs and man-
agement changes may make it especially difficult to maintain communica-
tion and smooth flow of the study from design through implementation.
However, even one champion of the project—someone who is enthusiastic
about the project, not just tolerant of it—within the facility may be the deter-
mining factor in its acceptance.
One example was in developing and implementing our “Hand and Paw
Study,” a randomized clinical trial in which cancer patients undergoing radi-
ation therapy were assigned to either have dog visits, friendly human visits,
or quiet reading sessions, three times weekly for 4 weeks. There was already
strong interest among the nursing staff in conducting research to test the ben-
efits of animal visitation to cancer patients (Johnson & Meadows, 2000b).
Members of the nursing staff had coordinated an evening dog visitation pro-
gram on the inpatient unit for several years but were not able to plan, fund,
and implement a study. This program paved the way for the study in the out-
patient radiation therapy unit because animals were already in the building
and staff members and patients viewed the inpatient program very
positively.
Thus, for our study, we contacted the medical director to describe the pro-
ject and elicit his support. We conducted a brief meeting with the nursing,
secretarial, and radiation therapy staff to describe the study and answer
questions. The fact that our study protocols caused no extra work for staff
members of this department greatly facilitated their support. Resistance
among members of the staff may be encountered, as there is commonly the
stigma associated with animals as dirty or dangerous. The best way to allay
the concerns of the staff and administration is by presenting evidence that
animals do not pose significant risks of infection or injury for patients.
If we had not had this early entrée into the facility, we would have begun
by talking with a clinical nurse specialist, or nurse manager for the clinical
units that we were interested in, or the director of nursing or vice president of
nursing services. In identifying a potential facility, there may be the greatest
likelihood of gaining entry into one that already has animal visitation pro-
grams in place. For facilities where this is not the case, it may be necessary to
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give the early contact persons descriptions of animal visitation programs
ongoing in other facilities.
In another one of our descriptive studies, we needed to identify dog own-
ers and non–dog owners to interview as we sought to identify whether pet
ownership and attachment were related to health, function, and social sup-
port. To locate dog owners, we needed to elicit the assistance of staff mem-
bers in a very busy veterinary clinic, so we approached the veterinarian in
charge, who was enthusiastic about the project (Johnson & Meadows, 2001).
He described the study to the staff and asked for volunteers to help identify
potential participants to invite to become involved in the project. His com-
mitment to the research enabled him to communicate enthusiasm for the
study to the staff. This was instrumental in their willingness to support our
project. Generating support for the project within the facility often takes
place simultaneously with the Institutional Review Board (IRB) approval
process.
Institutional Review Board Approval
Because IRB approval by the facility in which the research is to be con-
ducted is commonly needed in addition to the university IRB approval,
investigators must prepare the necessary materials for review. These may be
significantly different in length and content than those required by a univer-
sity. Particular issues may be raised, such as the ethical issue of withdrawing
the animal from patients at the close of the study when bonding may have
resulted. This issue may be addressed in several ways. For example, the
facility may want to adopt a visitation program with the animal, or the proto-
col may allow for the patient and the animal handler to arrange for visits to
continue with the patient after the study.
Another process that may be necessary is for the project to be reviewed
by the animal care committee of the university to ascertain that the animals
being used are treated humanely—issues such as what the risks are to the
animal during participation in the study and what plans have been made to
address these. This additional process may result in further delays in starting
the project.
Intervention research involving animal visitation may also be subjected
to additional review because of infection control concerns. The investigators
must be prepared with the latest data regarding zoonosis—transmission of
infectious organisms from animals to humans. This question will inevitably
arise. It is of such significance that we devote a subsequent section of this
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article to its discussion. It also has critical implications for recruiting partici-
pants, some of whom may be concerned about contracting an illness from
the animals used in the study.
Zoonotic Concerns
One of the most significant impediments to researching the beneficial
effects of animal-assisted activity/therapy is the considerable resistance of
many health care professionals to allowing animals in facilities such as hos-
pitals, long-term care facilities, and hospice centers, especially around
immunocompromised patients. It seems that this resistance often stems
more from a fear of starting zoonotic epidemics than from the possibilities of
bites, scratches, accidents (e.g., falls), or allergies. Hines (1996) pointed out
that there is little empirical work to show that the concerns about zoonoses
are valid. The risks to people are minimal and are outweighed by the benefits
when published guidelines are adhered to (Centers for Disease Control and
Prevention Healthcare Infection Control Practices Advisory Committee,
2001; Duncan, 2000; Greene, 1998; Marcus & Marcus, 1998; Weber &
Rutala, 1999). This resistance has been labeled as dated, irrational, exagger-
ated, unsubstantiated, political, and poorly thought out (Hines, 1996; Khan
and Farrag, 2000; Owen, 2001; Serpell, 1986). Authors have noted one is far
more likely to be infected with the flu or a cold virus or other lethal or debili-
tating disease(s) by another human than by an animal (Anonymous, 1992;
Serpell, 1986).
When the incidence of animal-related problems in animal-assisted activity/
therapy programs has been studied, they have been found to be almost non-
existent (Jorgenson, 1997; Lerner-Durjava, 1994). One 12-month study of
284 nursing homes evaluating the effects of live-in pets concluded that for
every 100,000 person hours of exposure there was 1 pet-related incident and
506 non–pet-related incidents (Stryler-Gordon, Beall, & Anderson, 1985).
Resistance to animal-assisted activity/therapy is reminiscent of the objec-
tions two centuries ago when Edward Jenner began injecting people with
cowpox virus to protect against smallpox. The “reason” cited was concern
about transforming people into semibovine humans (Serpell, 1986). A more
current, parallel concern was the belief that allowing children to visit inten-
sive care units would result in higher infection rates.
In animal-assisted interventions, rigorous screening and training of dogs
and their handlers is part of the protocol. When animals are vaccinated,
bathed regularly, screened for enteric pathogens, and treated for internal and
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external parasites on a monthly basis with commercially available and safe
products, the list of zoonotic conditions is reduced to a minimum.
Recruiting the Sample
Although highly desirable, it may be nearly impossible to recruit a com-
pletely random sample to conduct this type of research. For example, if for
the purpose of the study design, it is necessary to randomly recruit equal
numbers of pet owners and non–pet owners, it may be very difficult to iden-
tify this a priori from the same source. There may be unanticipated labor
costs and delays in conducting the study if it is necessary to identify who
among the potential sample are the pet owners or non–pet owners. However,
it is possible and may be desirable to randomly select and invite to become
involved potential participants from each category. Although this process
may make the sample less biased, it may also be costly in terms of researcher
or staff time to find the lists of potential participants.
A convenience sample may be more reasonable. In one of our studies, we
recruited pet owners from veterinary medical clinics, and non–pet owners
from community and church-related groups. Whereas for intervention stud-
ies being conducted in one particular clinical site it may only be necessary to
determine pet ownership status as a demographic variable, generalizability
of the findings may be compromised if the resultant sample comprises only
pet owners or non–pet owners.
Another issue in sampling is the need for greater diversity. The majority
of research conducted to date in this field has not systematically attempted to
study diverse groups. Thus, diverse ethnic representation in samples studied
has been extremely limited. Particularly in studies of ethnic older adults,
recruitment may be difficult due to fear from the lingering effects of prior
experiences in which animals—particularly dogs—were historically associ-
ated with racial brutality. Selecting an animal other than a dog for the inter-
vention is one way to avoid this problem. Perhaps the most innovative and
inclusive approach would be to offer participants choices between types of
animals for their intervention experience. This will make the study a bit
more complex—particularly in experimental designs—in terms of standard-
izing the intervention.
Although the desired sample size should be derived through power analy-
sis, practicality may loom as the investigator encounters potential partici-
pants who decline to participate. Common reasons include pet aversion,
allergies, or preferences. The same stigma that may be encountered among
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facility staff members may also be encountered among prospective partici-
pants; namely, that animals are dirty, potentially dangerous, or belong only
outside.
In estimating the numbers of potential participants available from a par-
ticular facility, it is wise to keep in mind that the actual sample accrued may
be considerably smaller than originally thought possible, leading to the need
for multiple sites. For example, in one of our studies, some potential partici-
pants declined involvement because there was a one-in-three chance (one
experimental/pet group and two non-pet control groups) of receiving the
animal intervention.
To counteract this potential problem, it will be helpful to carefully set the
selection criteria to control the potentially confounding variables of pet
ownership, preference, aversion, and allergies and to recruit only those who
are receptive to pets and are not allergic to the animal to be used in the inter-
vention. It may also be advisable to allocate a longer time span to recruit-
ment, use more than one recruitment site, or both. Adding recruitment sites
will likely involve more investigator/research assistant time spent in prepar-
ing additional IRB materials, conducting meetings to orient facility staff
members to the study, and traveling between sites to recruit and later to con-
duct the study. These constraints need to be factored into the study budget.
Depending on the sources of the animals and their handlers, there may also
be additional costs incurred for reimbursement or purchase of extra
equipment.
Another factor affecting recruitment and retention is the length of time
that the intervention and data collection takes. The best approach to prevent-
ing this problem is careful design of the study protocol and judicial selection
of study instruments to minimize participant burden.
Selecting Study Instruments
Intervention studies using animals may be, by nature, labor intensive for
the participant and for the investigator/research assistant. This is particularly
true if longitudinal designs with multiple data collection points are used. For
example, if participants are to receive several animal visits and to complete
instruments or undergo invasive data collection procedures at the close of
each visit, the importance of minimizing participant burden cannot be over-
emphasized. Nearly all participants in animal intervention studies, by virtue
of the fact that they are older adults or children and are hospitalized, institu-
tionalized, or in the process of receiving multiple painful or exhausting treat-
ments, may be negatively affected by overzealous batteries of instruments.
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Thus caution is warranted to prevent an exhaustion factor in data collection
not to mention problems with participant attrition.
With that caution in mind, to date the data collection instruments that
have been used in research involving animals run the full range of paper and
pencil questionnaires and rating scales. These seem to be as effective as with
studies in other areas of inquiry. However, in one of our studies where we are
non-invasively assessing stress among dogs that visit cancer patients, we are
using a behavior observation protocol to identify deviations from the dogs’
usual behavior. We consulted with a veterinarian who is board certified in
animal behavior who advised us regarding the behavioral indicators of stress
in dogs.
Observation of human behavior may be particularly appropriate for stud-
ies involving animals. Because human/animal interaction often involves
expression of emotions in ways different than in human-to-human interac-
tion, observation may be very helpful in lending context to what participants
report about their interactions with the animal. Because animals are per-
ceived by humans as nonjudgmental and unconditionally loving, partici-
pants may be more willing to express certain emotions or to tell particular
stories to an animal than to a human. For example, in one of our studies, a
large, burly man relayed to a small visiting dachshund, while stroking her,
the entire journey with cancer from his first symptom through diagnosis,
treatment, and hospice care. Without observation, we would have missed
this important context for describing the numeric study findings.
Implementing the Study
Before a complete research program is initiated, it is of great importance
to test the practicalities of animal-assisted interventions with a pilot study.
Even if the interaction with an animal and collection of specimens are done
within the framework of a particular clinical setting with only one patient, a
researcher could learn much from the pilot to prepare for the full research
project. In this way, certain pitfalls could be avoided or adaptations could be
made to the protocol to overcome particular obstacles. It also helps for the
personnel involved to set routines for the procedures; routines should not be
burdensome to the facility staff.
Keeping facility staff efforts to a minimum continues to be a central fac-
tor in determining the success of the project. Thus, study budgets need to
take into account that in today’s health care environment with chronic short
staffing and economic challenges, facility staff members should not be
counted on for significant work in the day-to-day operation of the study.
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Continuity of study staff workers is the best way to ensure that study proto-
cols are followed, potential participants are not missed, and study sampling
design integrity is maintained.
Contamination across the study groups is a common problem in this type
of intervention study. For example, participants in the experimental group
may describe the funny antics of their animal visitor with participants in the
control group, thus possibly confounding the study. Alternatively, staff
members or family members may talk with participants in the control group
about the presence of the animal or the responses of patients to the animal.
The investigator may control contamination by randomly assigning partici-
pants to the study groups and thoroughly orienting staff members to the
study. Then, careful scheduling of the intervention where possible (e.g., on
different clinical units) may help to prevent participants in the control group
from seeing or hearing about the animal visitor(s).
Several complications may arise during the study implementation phase.
For example, in one of our studies, scheduling outpatients’ dog visits
became burdensome for the handler who brought the dog to the study site
(Johnson & Meadows, 2000b). Conflicts arose with her work schedule so
that we needed to make alternative arrangements to take the dog home after
it completed its visits.
Logistical problems may also arise in getting the animal(s) to multiple
study sites. It may be necessary to use more than one visitor animal and more
than one handler, depending on the sample size and the timing of the animal
visits. However, this may pose a threat to the internal validity of the study
because the intervention may not be consistent across participants in the
experimental group.
Animal handlers are critical to the success of this type of intervention
research. They frequently devote a great deal of time, energy, and resources
to the project, particularly when the sample is large. Study protocols for the
animals requiring extra animal grooming, immunizations, and parasite treat-
ments are common and result in added expense for the handlers. Compensa-
tion, or at minimum, honoraria should be included in the study budget. Most
handlers are extremely dedicated and willing to undertake the extra commit-
ment. However, it is important not to take advantage of them so that they
become overly burdened during the study and are unable to continue
participating.
Selecting the type of animal to be used in the study may be based on sev-
eral factors. Although dogs are most commonly used in intervention studies,
there are disadvantages to this. Depending on the clinical setting and the tar-
get population, dogs—even very calm ones—may be more interactive than
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is desired. In a situation where less interaction is needed, for example with
highly agitated or unpredictable patients, it may be more appropriate to
introduce an aquarium. Investigators have successfully used self-contained,
self-cleaning aquaria with patients who have Alzheimer’s disease (N. Edwards,
personal communication, September 29, 2001). A decrease in blood pres-
sure has been recorded during positive interaction with birds and while look-
ing at fish in an aquarium, and it may be deduced that humans might experi-
ence the same benefits as during positive human/dog interaction. Such
extrapolation should, however, still be confirmed through research.
Although cats have been used very little in this type of research, they may
be very appropriate depending on the aims of the study and the clinical envi-
ronment in which it takes place. They may be less receptive to visitation pro-
grams because traveling is sometimes frightening to them. However, well-
socialized cats with few fears would be good candidates for this type of
research.
If dogs are used for the intervention, their selection as facilitators is criti-
cal. Clinical settings could be a threatening environment to dogs that behave
well in other environments. Dogs should be exposed beforehand to the clini-
cal situation where they have to operate to provide them the opportunity for
habituation to unfamiliar stimuli.
Behavioral characteristics that are not conducive to successful interaction
are dogs that are too excited (quick jerky movements, jumping up, running
around, panic, excessive licking, excessive tail wagging); dogs that are too
noisy (barking or whining); dogs that show any sign of aggression including
growling; dogs that show too much interest in their environment (or the
other dogs) instead of the patient; and generally disobedient dogs. Predict-
able (consistent) behavior by the dogs will contribute to the validity of the
experiment. It is much easier to achieve such behavior with docile than with
lively dogs. The Delta Society has delineated protocols for training dogs and
handlers for participation in animal-assisted interventions and for imple-
mentation of programs in clinical settings (URL: www.deltasociety.org).
In conducting animal intervention research, the investigators must be
prepared that some participants and some animals (e.g., dogs) will not
match. For these situations, it may be important to have more than one
“intervention dog” available so that it is possible to use a dog that the partici-
pant prefers. The other alternative is to use another species, such as cats,
birds, or fish.
If dogs are used, it is necessary to show a patient how to interact posi-
tively with a dog. Such interaction may be only to watch, hear, and smell the
dog; it may be talking to the dog; it may be stroking and touching the dog, or
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it may include all of the above. In the case of touching and stroking, during
the initial contact, dogs prefer to be touched on the lower side of the body
rather than from the top. It is especially important for patients to avoid
touching the head from above or from the front during the first contact. An
ideal pattern of touch would have the patient’s hand moving from the lower
parts of the body to the back and then to the shoulder, neck, and head area.
Most dogs like to have their ears gently massaged if there is no ear infection
present. Standardization of the interaction will further contribute to a consis-
tent intervention for measuring/experimental purposes. This type of instruc-
tion should be part of any animal interaction that humans have during
studies.
It is also critical that any animals used should pass a health check (includ-
ing monitoring vaccination dates) by a veterinarian before patients interact
with them. Hygiene procedures should be in place as part of the study proto-
col with regard to animal management (especially to allow for normal elimi-
nation behavior) in clinical settings. The protocol should specify that a han-
dler must be present during the duration of the intervention to ensure total
control of the animal at all times. All patients’ concerns should be attended
to—for example, research interventions must take place in areas away from
patients who are allergic to particular animals.
The experiences of the animal prior to coming to the study site may influ-
ence its behavior to the point that patients who interact earlier in the inter-
vention day may have a different experience with the animal than those who
interact later. Ideally, the animal’s usual routine should be maintained for at
least an hour before coming to the study site, so that external stressors are
minimized.
When physiological parameters are to be studied, taking baseline values
for every participant at about the same time of the day takes into consider-
ation the circadian cycle, and it individualizes the measurements. Such
activities should also fall within the routine care program of the clinical set-
ting. Physiological measurements following the intervention should be
taken the same day as the baseline, and if the measurements are taken over a
number of days, baseline values should be taken before every follow-up
intervention. Patients should be settled down (5-10 minutes) with the ani-
mal, before baseline values are taken, and specimens should be collected
with a minimum of physical stress to the patient.
A problem that might arise is maturation effects over time as well as
effects of other therapeutic interventions that may run concurrently with the
animal intervention. If animals are used over a period of time, a graph of
daily progress should be drawn that could record any unexpected negative or
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positive reactions in relation to the baseline levels assessed prior to the ther-
apy. Deviations might indicate unacceptable external influences on the animal-
assisted intervention.
To study physiological changes in patients, it is important to evaluate
such changes in relation to healthy persons. Based on such a program of
research (Odendaal, 1999; Odendaal & Lehmann, 2000) that was aimed at
determining physiological parameters of both humans and dogs during posi-
tive interaction, there are several additional precautions that must be taken.
For example, parameters for neurochemical changes to consider could be
increases of beta-phenylethylamine, dopamine, beta-endorphin, oxytocin,
and prolactin in blood plasma as well as an increase of the precursor of sero-
tonin in urine (all of which are associated with positive interaction or affilia-
tion behavior) and a decrease of cortisol in blood plasma (an indication of
decreased stress). It is recommended to use a profile of neurochemical
changes because of the interplay of these neurochemicals during positive
interaction. If a behavioral pattern is associated with more than one
neurochemical change, then the effects should be studied accordingly. If it is
not possible to determine a comprehensive profile because of practical or
financial limitations, then phenylethylamine and oxytocin may be the most
indicative parameters. The former indicates an immediate affiliation and the
latter a long-term affiliation, which is associated with bonding (attachment
or longer-term ownership).
A decrease of at least 5% in blood pressure from the baseline could be a
sufficient indicator of neurochemical changes and thus provide the optimum
time to collect specimens for analyzing neurochemicals. Desired physiolog-
ical effects could be achieved after an average period of 15 minutes of posi-
tive interaction with an animal. Therapy sessions thus need not be very long.
There is a threshold for the benefits of positive interaction in humans as well
as animals, and one should not exceed such a period during a single session.
It is important to specify what movement during the interaction will be
expected from and allowed by the patient (e.g., if an automatic blood pres-
sure apparatus is attached to the patient, only the free arm should be used to
touch the animal).
It is recommended to also observe and record the patient’s overt behavior
during the intervention because there should be a correlation between such
behavior and physiological parameters. This information may provide
important cues in cases when the detection of neurochemical changes is
impossible.
Comparison is recommended of laboratory findings from ill patients in
clinical research with results that were achieved by studying physiological
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parameters of healthy persons. Such a comparison might contribute to the
establishment of possible neurochemical profiles that are specific for certain
disease conditions.
FORGING AHEAD
There are many critical questions that are as yet unanswered in animal-
assisted intervention research. For example, we do not yet know the entire
range of patient populations for whom this intervention may be beneficial.
The “dosage” factor of the most beneficial timing, frequency, length, and
content of the animal intervention is unknown. Yet to be determined are the
differential effects of human interaction with various species and their appli-
cability to particular clinical situations. Finally, there has been no investiga-
tion of the effect of selecting the preferred animal to interact with, and eth-
nicity has not been explored in relation to health benefits of human/pet
interaction.
Finally, better designed experiments are needed to enhance the credibil-
ity of animal-assisted interventions so that reimbursement for them can
begin, and more patients who could potentially be benefited can receive
them. This may be very important given the need to expand our intervention
repertoires to be able to address the increasingly complex health problems of
an aging world.
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