Content uploaded by Lori Marino
Author content
All content in this area was uploaded by Lori Marino
Content may be subject to copyright.
1
In press. Anthrozoos.
Dolphin Assisted Therapy: More flawed data and more flawed conclusions
Lori Marino1 and Scott O. Lilienfeld2
1Neuroscience and Behavioral Biology Program, Emory University, Atlanta, GA
2Department of Psychology, Emory University, Atlanta, GA
Corresponding author:
Lori Marino
Neuroscience and Behavioral Biology Program
Emory University
1462 Clifton Road, Suite 304
Atlanta, GA 30322
Phone (404) 727-7582, Fax (404) 727-7471, lmarino@emory.edu
Abstract
2
Dolphin Assisted Therapy (DAT) is an increasingly popular choice of treatment for
illness and developmental disabilities by providing participants with the opportunity to
swim or interact with live captive dolphins. Two reviews of DAT (Marino & Lilienfeld,
1998) and Humphries (2003) concluded that there is no credible scientific evidence for
the effectiveness of this intervention. In this paper, we offer an update of the
methodological status of DAT by reviewing five peer-reviewed DAT studies published in
the last eight years. We found that all five studies were methodologically flawed and
plagued by several threats to both internal and construct validity. We conclude that
nearly a decade following our initial review, there remains no compelling evidence that
DAT is a legitimate therapy or that it affords any more than fleeting improvements in
mood.
Keywords: dolphin assisted therapy, DAT, swim with dolphin, validity
Dolphin Assisted Therapy (DAT) is an increasingly popular choice of treatment for
illness, disability, and psychopathology in children and adults (Whale and Dolphin
Conservation Society, 2006). It involves swimming and interaction with dolphins,
3
typically in captivity. DAT formally began in the 1970’s and over the years has grown
into a highly lucrative business with facilities all over the world, including the United
States, Mexico, Israel, Russia, Japan, China, and the Bahamas, to name only a few
countries. The claims made by these facilities have been subject to little or no scientific
scrutiny. Moreover, there has been no significant increase in the rate of peer-reviewed
papers on DAT from the 1970’s to the present. Yet DAT programs continue to
proliferate. As a consequence, DAT’s popularity greatly outstrips its meager research
base.
Eight years ago we published a review (Marino and Lilienfeld 1998) of the available
peer-reviewed DAT literature at the time, focusing on two papers by David Nathanson
and his colleagues (Nathanson et al. 1997; Nathanson 1998). These authors advanced
several extremely strong claims concerning the efficacy of DAT for treating severely
disabled children: (1) DAT significantly increases attention span, motivation, and
language skills; (2) DAT achieves these results more rapidly and more cost-effectively
than conventional therapies; and (3) DAT produces positive treatment effects that are
maintained over a long-term period (i.e., at least one year).
In our original paper (1998) we presented a methodological analysis of these two studies
and the claims derived from them by applying standard criteria for scientific validity from
four established sources (Cook and Campbell, 1979; Kazdin and Wilson, 1978; Kendall
and Norton-Ford, 1982; Shaughnessy and Zechmeister, 1994). We found no fewer than
eleven independent methodological weaknesses in both studies that seriously undermined
4
their scientific validity. These shortcomings included the absence of adequate comparison
or control groups, unreliable, subjective and potentially biased raters, and, analytic
methods that did not allow the reader to ascertain whether any children were harmed by
DAT. We concluded:
“...serious threats to validity and flawed data analytic procedures render the findings of
Nathanson and colleagues uninterpretable and their conclusions unwarranted and
premature... the current evidence for the efficacy of DAT can at best be described as
thoroughly unconvincing” (Marino andLilienfeld 1998, p. 199). At the time of our
review, these two studies were the only peer-reviewed investigations of the therapeutic
effects of DAT. Therefore, as of 1998 there was no credible scientific evidence for the
effectiveness of this intervention.
A more recent and similar critical review of DAT was published five years later by
Humphries (2003). In her excellent analysis of the peer-reviewed DAT literature,
Humphries evaluated six DAT studies and found that all six lacked experimental controls
and neglected to control adequately for major threats to validity and alternative
explanations for the results. She concluded that:
“...the available research evidence, as examined in this synthesis, does not
conclusively support the claims that DAT is effective for improving the behaviors
of young children with disabilities. More specifically, the results of the synthesis
do not support the notion that using interactions with dolphins is any more
effective than other reinforcers for improving child learning or social-emotional
development.” (Humphries, 2003, p. 6)
5
Finally, Brensing, Linke, and Todt (2003) evaluated the claim that DAT works through
healing by ultrasound. The authors conducted an observational study of the behavior of
dolphins in two DAT programs to determine if their behavior was consistent with the
hypothesis that they were echolocating on human participants (and thus ostensibly
providing “healing energy” through ultrasound). Brensing et al. concluded that the
dolphins’ behavior was not consistent with this hypothesis and therefore did not meet the
minimal requirements for common ultrasound therapies. Therefore, there is no scientific
evidence that echolocation can heal, nor that dolphins echolocate on humans in a manner
even minimally consistent with that claim.
In this paper, we update the DAT literature by reviewing the five peer-reviewed DAT
studies published since 1998. We focus on peer-reviewed papers because these articles
presumably represent the “best” evidence for the efficacy of DAT. We argue that an
updated analysis of DAT is warranted given the increasing popularity of this activity.
Humphries (2003) reviewed peer-reviewed studies that ranged from 1989 to 1999, two of
which had already been evaluated by Marino and Lilienfeld (1998). Brensing, Linke, and
Todt (2003) based their conclusions on data taken from their studies of DAT at two
facilities and did not provide a methodological evaluation of the peer-reviewed literature.
In the present article, we pick up where our 1998 paper left off by evaluating the
methodological validity of the five peer-reviewed DAT studies that have been published
since then.
Method
6
We examined a total of five papers describing studies using DAT. These are Antonioli
and Reveley (2005), Iikura et al. (2001), Lukina (1999), Servais (1999), and Webb and
Drummond (2001). The authors of four of the studies reported improved behavioral
outcomes for subjects receiving DAT. The lone exception was Servais (1999), who
reported positive outcomes in only one of the two experimental groups in her study.
Beyond the ambiguous results reported by Servais (1999), we found no other published
studies in which negative findings were noted.
We searched for peer-reviewed studies on DAT in several ways. First, we submitted the
search terms ‘dolphin assisted therapy’ and ‘dolphin therapy’, to the GOOGLE Scholar
search engine. Second, we used these same terms to search GOOGLE for the websites of
DAT facilities and searched any bibliographies listed on these websites. Third, we used
these terms in a search of the Current Contents database. Fourth, we conducted a
comprehensive search of all papers on DAT from 1999 to the present in the following
peer-review journals: Anthrozoos, Society and Animals, Applied Animal Behaviour
Science, and Zoo Biology. Fifth, we reviewed the reference sections of articles identified
through the above means for further relevant studies.
As in our 1998 paper, we assessed the validity of each study according to the
standard criteria put forth by four sources: Cook and Campbell (1979), Shadish, Cook,
and Campbell (2002), Kendall and Norton-Ford (1982), and Shaughnessy and
Zechmeister (1994). These sources describe a set of threats to experimental validity that
should be avoided in experimental research. The presence of even one major threat to
7
validity can render a study’s findings difficult, or in some cases even impossible, to
interpret.
Table 1 displays several important threats to validity, their definition, and whether they
are present in each of the five studies. Most of these threats relate to either internal
validity, i.e. the methodological soundness of the study, or to construct validity, i.e., the
soundness of the measures as indicators of the constructs examined by the investigators.
In the interest of space, we limit ourselves here to the most serious threats to validity.
Results
Table 1 shows that each of the five studies we examined violated several
important criteria for validity. Moreover, because of inadequate experimental control,
two threats to construct validity, i.e., nonspecific effects and construct confounding,
plagued all of these studies. Because these threats to validity are so ubiquitous in the
DAT literature, we discuss them in depth in separate sections and follow with more
specific points concerning each of the individual studies.
Nonspecific effects
Nonspecific effects are improvements from influences that are not specific to the
intended treatment, and that are shared by a wide variety of other treatments. They are
generic effects of the treatment rather than the result of the intended therapeutic
ingredient(s). Two relevant subcategories of nonspecific effects are placebo effects and
novelty effects. The placebo effect is the well-documented but little understood
improvement that derives from subjects’ expectation of improvement. Novelty effects
are the general energizing and uplifting effects of a new, exciting experience. Because of
8
its nature, DAT is particularly prone to these two nonspecific effects. Furthermore, many
nonspecific effects are notoriously transient. Therefore, any study of DAT must
incorporate rigorous procedures for minimizing these nonspecific effects and, in
particular, must include ways to assess longer-term effects of the treatment.
DAT is vulnerable to placebo effects in part because DAT is typically marketed to
participants and their family members as highly efficacious and in part because the nature
of the treatment is evident to participants. Moreover, none of the studies we reviewed
used a control that eliminates or substantially minimizes this effect by eliminating cues to
treatment condition. DAT is vulnerable to novelty effects because of the obviously new
and exciting experience of swimming with and interacting with a large, intelligent,
charismatic animal. The proper control for novelty would be exposure of the control
group to another novel attractive animal, while keeping all else equal. In this way, both
groups would have similar reason to believe that they had received the relevant treatment,
and both would be subject to the excitement of interacting with an exotic animal. At the
very least, DAT should be compared with other animal assisted therapies in addition to a
no-treatment control group. If one found differential effects of dolphins versus other large
charismatic animals, it would be important to seek possible specific therapeutic
ingredients inherent in DAT. In contrast, if both dolphin and other animal groups
improved equally, this would suggest a generic characteristic of DAT as an example of a
temporary “feel-good effect” (activating effect) received from any animal therapies – and
indeed any therapies involving exciting and novel features.
Construct Confounding
9
Construct confounding occurs when there is a failure to take into account the fact that the
experimental procedure may involve more than one active (effective) ingredient. In
DAT, the experimental treatment typically consists of a complex assortment of
ingredients in addition to interacting with a dolphin per se, such as swimming in water,
being near water, being outside, and receiving attention from human professionals.
Moreover, the dolphin itself is a complex stimulus that can be deconstructed into various
potentially therapeutic components, such as the size and touch of the animal and the
opportunity for interaction with the animal. Because none of the DAT studies we
examined adequately controlled for these possibilities, they are all subject to construct
confounding. In the psychotherapy literature, construct confounding is typically
decomposed by means of dismantling studies (Kazdin, 1994), which separate the
potential effects of different treatment ingredients by creating different experimental
conditions containing these effects. And although we are not suggesting there is one
single ideal control for DAT, no DAT study has included an adequate subset of the many
control groups that would be required for even a minimally effective dismantling
strategy.
Antonioli and Reveley (2005)
Antonioli and Reveley (2005) conducted a single blind randomized controlled experiment
to determine if swimming and interacting with dolphins at a captive facility in Honduras
lowered scores on depression and anxiety scales. The total sample consisted of 30 men
and women (prior to subject drop outs) with mild to moderate depression scores on the
ICD-10 (i.e., the International Classification of Diseases, 10th edition) who also scored at
10
least 11 on the modified Hamilton rating scale for depression at baseline after four weeks
without medications. The experimental group (the animal care program) consisted of 13
subjects who played with, swam with, and “took care of” dolphins while in the water with
them. The control group (the outdoor nature program) consisted of 12 subjects who
swam and snorkeled in the barrier reef and experienced a similar degree of individualized
human contact as those in the experimental group but in the absence of dolphins. Both
programs ran simultaneously from Monday to Friday for one hour a day for two weeks.
The authors conducted pre-treatment and post-treatment ratings of depression with the
Hamilton Rating Scale and the Beck Depression Inventory, and measured anxiety with
the Zung Self Rating Anxiety Scale.
Antonioli et al. found a significantly greater improvement in depression scores in the
experimental group than in the control group. They also found no differences in the
anxiety scores (although the authors argued the lack of statistical significance could be
due to the fact that only a subset of the sample was clinically anxious prior to treatment).
Antonioli et al. concluded that DAT is more effective than “water” therapy for treating
mild to moderate depression. However, this conclusion is compromised by several
shortcomings.
First, the authors acknowledged that a limitation of their study is that the participants
were not blind to treatment. Therefore, demand characteristics might have influenced
participants’ responses. The authors, did, to some extent, guard against potential demand
characteristics by emphasizing to subjects that they were taking part in a research study
11
rather than a clinical intervention and should therefore not expect any improvement.
Still, it is not known whether subjects may have discerned the true nature of the study
despite this information.
The second major shortcoming is that the control condition did not account for the
potential effects of interacting with any charismatic animal, in this case, a dolphin. The
experimental group swam with dolphins, whereas the control group did not interact with
any other analogous animal. Participants in the control group swam along a coral reef and
interacted with the experimental personnel. However, there was apparently no
introduction of other large mobile animals, such as fish, that could have served as a
salient stimulus control for the dolphin. Therefore, because of the lack of an appropriate
control group, participant outcomes could have been due to nonspecific effects, including
placebo and novelty effects. Therefore, the authors’ inference that the dolphin was the
effective therapeutic ingredient is premature. The third potential threat to validity in this
study is informant bias. Because the authors’ relied on self-report measures of
depression, the subjects, who were not blind to treatment, could have selectively recalled
the amount of their improvement as a consequence of expectations, hopes, and even
effort justification (i.e., the psychological need to justify to oneself the time, expense, and
energy invested in the treatment).
Fourth, the authors acknowledged that they did not perform a follow-up study of the post-
treatment ratings. Therefore, the only justifiable conclusion they can draw is that there
was a difference between the experimental and control groups immediately following
12
treatment (and even that conclusion is suspect given the flaws discussed above). It is not
known whether this difference existed even one day after the post-treatment assessment
and, moreover, whether any subjects deteriorated. This lack of follow-up assessment is a
major shortcoming, as it renders the results susceptible to novelty or short-term activating
effects.
Related to this point, the authors touted the benefits of DAT over conventional drug
therapy or psychotherapy by claiming that depression is relieved after only two weeks of
dolphin therapy but requires at least four weeks to improve with mainstream therapies.
The authors neglected to point out, however, that the conventional treatments often exert
long-term effects. In contrast, the authors provided no evidence that dolphin treatment
produces any effects beyond the immediate aftermath of the treatment.
Finally, Shadish, Cook, and Campbell (2002) refer to a threat to construct validity known
as “resentful demoralization”, which may occur when members of a control group
become aware that they are receiving a less desirable treatment or no treatment, thereby
becoming disappointed and resentful. These negative emotions can then affect their
responses. Resentful demoralization may be responsible for negative control group
outcomes that falsely produce the appearance that the treatment was effective. Antonioli
and Reveley appeared to be aware of this possibility and attempted to mitigate it by
allowing the control group to swim with dolphins at the conclusion of the treatment.
However, because the control group was allowed to swim with the dolphins only after the
13
final evaluation, the possibility of resentful demoralization was not adequately
eliminated.
Iikura et al. (2001)
Iikura et al. (2001) sought to determine whether the presence of dolphins enhanced the
effectiveness of seawater therapy for atopic dermatitis. Thirty six patients with atopic
dermatitis were subjected to seawater therapy (bathing in seawater at a beach) with
dolphins present for six days, and 27 received the seawater treatment without dolphins for
six days. No other details were offered about the seawater therapy, the condition of the
patients, the nature of exposure to the dolphins, or any other methodological components
of the study. Yet the authors concluded that all parameters of the atopic dermatitis
improved in both groups and, more important, that the dolphin group experienced “less
stress and pain” during the seawater therapy than the non-dolphin group. Furthermore,
the authors claimed that the “patients also enjoyed swimming with the dolphins.” They
concluded that dolphins were “very useful as a pain reliever during therapy...” (p. 390).
It is difficult to evaluate the methodology and conclusions of Iikura et al. given the
marked paucity of information in the paper regarding how the study was conducted.
Moreover, the authors’ conclusions are vague and subjective. In the absence of
appropriate methodology, it can only be concluded that the Iikura et al. study is wholly
uninterpretable and offers no credible support for the efficacy of DAT. Therefore, as far
as can be determined, most of the potential threats to validity described in Table 1 apply
to Iikura et al.
14
Lukina (1999)
Lukina (1999) employed a single-group pretest-posttest design to determine the effects of
DAT on “psychoneurological” functioning in healthy children and those with various
diseases. The subjects were 57 healthy children, 30 with “infantile neurosis,” 25 with
mental retardation and autism, and 35 with other unspecified diseases. All of the children
swam with and interacted with captive dolphins for 10-15 minute periods over 5 – 10
sessions. Although Lukina indicated that a number of psychological tasks were presented
to the children during these sessions, she did not describe them. Likewise, although she
stated that her outcome measures included many tests and observations, none were
described in sufficient detail. Therefore, most of the threats to validity in Table 1 cannot
be ruled out.
Lukina (1999) reported that the variability of cardiac rhythms in all groups increased after
the dolphin exposure and claimed that “this confirms the redistribution of the
psychoemotional dominants in the course of contacts with the dolphin, a fact that opens
possibilities for rehabilitation measures and psychotherapy.” (p. 678) but it is unclear
what the author meant by “psychoemotional dominants” or how they are related to
cardiac rhythms. Furthermore, the author claimed that after the dolphin sessions, parents
and facility workers noted the emergence of “new-individual personal qualities,” such as
kindness and self-control. Nevertheless, these observations were subjective and
unquantified. Also, Lukina claimed that many disease symptoms in the “infantile
neurosis” group, such as depression, night phobias, hysteria, and enuresis, diminished and
that all the children responded “positively” to the dolphin sessions. Nevertheless, she
offers no data or description of the assessment instruments to support these purported
15
outcomes. Finally, because psychotherapy was a part of the system of treatment, it is
possible that any improvement in the subjects was due to interventions other than the
dolphin component per se, thereby making multiple interference intervention a potential
threat to validity.
In addition to these flaws, the pivotal weakness of the Lukina study is the absence of a
control group consisting of children who did not swim with dolphins. Therefore, the
study does not meet the minimal criteria for basic experimental design. This flaw alone
renders the Lukina study difficult to interpret even without the myriad other threats to
validity. Although sophisticated single-subject designs for drawing causal conclusions
exist (Shadish, Cook, and Campbell, 2002), simple A-B (pretest-posttest) designs are
typically extremely limited in internal validity.
Servais (1999)
The design of this study included two experiments, lasting 16 and 14 months,
respectively. The first included three groups of 3 autistic children each. The dolphin
group was taught a cognitive task while interacting with a dolphin and trainer at dockside.
The two control groups were a classroom group and a computer group in which the same
cognitive task was taught in their respective settings. The second experiment included a
dolphin group and a classroom group. Servais did not report the actual age of the
participants but indicated that the developmental ages were 1 – 3 years. All sessions were
held on an individual basis and lasted 15-20 minutes. The dolphin and computer groups
were given 10-35 “habituation sessions” to familiarize themselves with the new setting
16
and were required to master some simple behaviors before moving on to the next phase of
the study. All groups received pre-tests followed by 10-15 “learning sessions” in which
other cognitive tasks were given, and then post-tests.
It is not clear whether the pre-tests and the post-tests were the same across or within
groups. Therefore, instrumentation effects (the effects of changing dependent measures at
different times in the study) might be present. Besides post-test performance, the other
outcome measure was a rating of attention based on videotaped observations by the
author. Because the author was the only person to code behavioral outcomes, it is
possible that experimenter expectancy effects influenced the findings.
Servais (1999) found that the first dolphin group learned the tasks better than the other
groups, but reported no other differences between groups. In particular, the second
dolphin group did not perform better than the control group. Servais concluded that the
positive results were due to the emotional interaction between the experimenters and
children and that better-designed studies may “make the ‘animal effect’ disappear” (p.
14).
Despite Servais’ appropriate cautions about her findings and the effects of DAT, it is
worth noting several threats to validity. In addition to experimenter expectancy effects
and potential instrumentation effects, demand characteristics are impossible to rule out.
Moreover, the authors’ conclusion that the dolphin may not have been as important for
improvement as other components of the treatment point saliently to the possibility that
17
other aspects of the treatment procedure (such as swimming outdoors) besides the
dolphin interaction were responsible for the reported effects.
Webb and Drummond (2001)
Webb and Drummond (2001) investigated the psychological effects of swimming with
dolphins at a marine park in Australia. Subjects consisted of a wide age range of male and
female teenagers and adults without known or, at least, measured clinical pathology. The
subjects were paying participants and had been on a waiting list for up to six months. In
the well-being study, the experimental group consisted of 74 females and 25 males who
swam with four dolphins in groups of four for 25-30 minutes. The control group
consisted of 14 females and 15 males who swam at a beach adjacent to the marina in the
absence of dolphins. Both groups self-reported their feelings of well-being pre-treatment
and post-treatment. In the anxiety study, self-reported anxiety ratings were obtained from
12 females and 7 males who swam at a beach resort for 20-30 minutes in the presence of
wild dolphins (the experimental group). The control group consisted of 13 females and 8
males who swam at the same beach after the dolphins left.
In the well-being study, subjects completed a self-report questionnaire designed to
examine their perceived levels of well-being immediately before and after their swim.
Psychological well-being was defined as how “positive” each participant felt at the
moment. Physiological well-being was defined as how energetic each participant felt.
The participants reported these feelings on a scale of 1 to 100 for each questionnaire item.
In the anxiety study, subjects completed the “state” component of the State-Trait Anxiety
Inventory immediately before and after their swim.
18
Webb and Drummond found that, in the well-being study, the experimental group rated
their well-being significantly higher than the control group prior to the treatment. This
finding was presumably due to the positive anticipation of swimming with dolphins in the
experimental group. The well-being ratings of both groups increased post-treatment, but
ratings were significantly higher for the experimental group than the control group.
However, the authors found, following an analysis of covariance, that the pre-treatment
difference between the groups accounted for the differences that persisted after
swimming. Therefore, there was no significant effect of swimming with dolphins on
well-being. In the anxiety study, there were no significant pre-treatment differences in
anxiety between the experimental and control groups. The authors found a significant
decrease in self-reported anxiety in the experimental group, but not in the control group.
From these results, Webb and Drummond concluded that anticipation of a new and
exciting experience, and swimming itself, increase well-being. In addition, they
concluded that swimming specifically with dolphins may lower anxiety.
Because, of the two studies, only the anxiety study revealed significant differences
between the experimental and control groups, we focus on the anxiety study here.
However, all of the threats to validity in the anxiety study also apply to the well-being
study. In the anxiety study, subjects swam in the ocean during a visit by wild dolphins.
Prior to swimming with the dolphins, the subjects were told that dolphins appeared at the
site on a daily basis. Therefore, the subjects were led to anticipate a swim with dolphins
as they waited on the beach along with members of the public who were also hoping for a
19
dolphin encounter. The control group swam in the same area after the dolphins left and
did not expect to see dolphins because they were swimming after the period when
dolphins usually arrived.
Nevertheless, there are several problems with comparisons of the experimental and
control groups. The authors stated that they did not limit the number of swimmers who
swam with the dolphins. It is possible and even likely that there were more swimmers in
the water during the experimental condition than during the control condition. The
authors acknowledged that there was no limit on the number of people allowed in the
water while the dolphins were present. Given that they reported groups of people waiting
on the beach to swim with the dolphins, it seems plausible, if not likely, that there were
more people in the water accompanying the experimental group than the control group.
Moreover, there was no apparent effort to make the experimental and control group
comparable on that dimension. Therefore, decreased anxiety in the experimental
condition could have been attributable to interacting with more people.
In addition, if all the subjects were swimming together during the dolphin encounter, then
it is likely that they experienced the emotional contagion of positive feelings and
excitement that accompany seeing dolphins. This implies that the “therapeutic agent” in
this condition may have been the experience of swimming with other happy and excited
people. The reported effects may have had nothing to do with dolphins per se. Because
the authors did not control for this confounding factor (or, at least did not offer evidence
that they did), we cannot conclude that the significant decrease in anxiety in the
20
experimental group was due to the presence of the dolphins. Moreover, the authors
offered no information concerning how participants interacted with the wild dolphins or
even if any interacted directly with a dolphin. Because this information was not
provided, there is no means of determining to what “treatment” the experimental group
was actually exposed.
As in Antonioli and Reveley (2005), subjects were not blind to condition and were asked
to self-report on their anxiety level. Consequently, it is not possible to rule out either
demand characteristics or informant bias. Informant bias based on effort justification may
have played a significant role because the subjects were visitors to a local marine park
who paid to participate in a dolphin swim experience; moreover, some waited six months
for the opportunity. If the subjects in the experimental group were those who waited
longer for their opportunity to participate than those in the control group, then bias due to
effort justification becomes possible.
Conclusions and Summary
In summary, the abundance of serious threats to validity in the five studies we examined
renders each of their conclusions questionable at best, and entirely unwarranted at worst.
All of the studies are vulnerable to nonspecific effects, including placebo and novelty
effects, and construct confounding. In addition, each of the studies contained several
other methodological weaknesses that render the conclusions doubtful.
21
However, these five studies varied considerably in methodological rigor. Of the studies
reviewed, Antonioli and Reveley (2005) is the most methodologically rigorous, as it
includes controls for more potential confounds than the other studies. This study
implemented a number of commendable methodological features, including randomized
assignment of subjects to conditions, pre- and post-treatment blind raters of outcomes,
procedures to minimize demand characteristics, the use of standard validated assessment
instruments (the Hamilton Depression Rating Scale, the Beck Depression Inventory, and
the Zung Self-Rating Anxiety Scale), and the application of appropriate statistical tests.
In this respect, Antonioli and Reveley’s study is clearly methodologically superior to
Nathanson et al. (1997) and Nathanson (1998). However, even the laudable attempts of
Antonioli and Reveley do not eliminate the presence of important validity threats, such as
resentful demoralization and informant bias, nor the ever-present problems of nonspecific
effects and construct confounding. Therefore, Antonioli and Reveley (2005) falls short of
providing a valid test of DAT efficacy and stands as an important reminder of how far the
DAT literature must progress to meet minimal standards of methodological quality. .
Of the remaining four studies, none come close to the methodological quality of
Antonioli and Reveley. Most of these studies are plagued by potential experimenter
expectancy effects that could have been eliminated by the inclusion of raters blind to
experimental condition. In addition, these studies were bedeviled by a host of other
threats to validity (e.g. history, maturation, testing, regression) as well as a paucity of
reported information concerning basic methods and procedures. Moreover, none of the
studies included a follow-up assessment of the reported short-term improvements.
22
Most problematic are construct confounding and nonspecific effects (including placebo
and novelty effects), both of which appear to be ubiquitous in the DAT literature. None of
the five studies incorporated adequate controls for these two validity threats.
Minimization or elimination of construct confounding would require that both the
experimental group and the control group be exposed to the same or at least highly
similar procedures and stimuli with only the key ingredient – the dolphin per se – as the
differential treatment component between groups.
Placebo effects can be minimized or controlled by a blind study in which participants are
not afforded any information that would provide them with clues regarding their
assignment to treatment condition. Novelty effects can be controlled for by exposure of
the control group to another novel attractive animal (e.g., a horse, dog, or another aquatic
mammal) while keeping as many other variables as possible equal. Therefore, before
concluding that DAT possesses specific efficacy that could not be attained with a variety
of alternative treatment conditions, authors must offer sufficient evidence that the same
results would not be achieved with another large, charismatic attractive animal used in
the same procedures. If the proper tests were conducted and the control and treatment
groups were found to improve equally, one would need to conclude that there is nothing
special or necessary about the dolphin per se in DAT. If the DAT group improved
significantly more than the control group, then perhaps DAT could be considered a
potentially therapeutically interesting intervention, although pragmatic issues of
accessibility, expense, and risk would remain. So far, however, no studies have met this
23
challenge and compared DAT with an appropriate control group - one exposed to
identical procedures using a similar animal - within the same study.
Given that dolphins are highly attractive and interesting animals to most people, the
likelihood of novelty effects raises particularly troubling concerns regarding the DAT
literature. Most worrisome is the conspicuous absence of evidence for long-term
improvement from DAT. Despite DAT’s extensive promotion to the general public, the
evidence that it produces enduring improvements in the core symptoms of any
psychological disorder is nil. Occam’s razor suggests that it is probably most
parsimonious to interpret improvements from DAT as a temporary “feel good effect” of a
highly positive and exciting experience. From this perspective, there is little reason to
believe that DAT is a legitimate therapy or that it constitutes much more than
entertainment.
The surprising paucity of scientific evidence for the long-term effects of DAT raises
profoundly troubling ethical questions regarding its widespread use and promotion. There
is abundant evidence for injuries sustained by participants in DAT programs ((Frohoff
and Packard, 1995; Samuels and Spradlin, 1995; Webster, Neil, and Madden, 1998).
Moreover, interactions between dolphins and humans carry a significant risk of infections
and parasitism for both humans and dolphins (Geraci and Ridgway, 1991). Therefore,
DAT poses important ethical questions from the standpoint of human and captive dolphin
welfare. At the very least, we believe that DAT practitioners should be required to inform
parents and, when relevant, participants, of the absence of evidence for DAT’s enduring
24
effects on psychological symptoms. Only then can consumers of DAT make adequately
informed decisions regarding the costs and benefits of this unsubstantiated intervention.
References
Antonioli, C. and Reveley, M. A. 2005. Randomized controlled trial of animal facilitated
therapy with dolphins in the treatment of depression. British Medical Journal 331: 1231
1234.
Brensing, K., Linke, K. and Todt, D. 2003. Can dolphins heal by ultrasound. Journal of
Theoretical Biology 225: 99-105.
Cook, T. D. and Campbell, D. T. 1979. Quasi-experimentation: Design and analysis
issues for field settings. Boston, Massachusetts: Houghton Mifflin.
Frohoff, T. G. and Packard, J. M. 1995. "Interactions between humans and free-ranging
and captive bottlenose dolphins." Anthrozoös 8:44-54.
25
Geraci, J. R. and Ridgway, S. H. 1991. On disease transmission between cetaceans and
humans. Marine Mammal Science, 7: 191-194.
Humphries, T. L. 2003. Effectiveness of dolphin-assisted therapy as a behavioral
intervention for young children with disabilities. Bridges: Practice-Based Research
Synthesis 1: 1-9.
Iikura, Y, Sakamoto, Y., Imai, T., Akai, L., Matsuoka, T., Sugihara, K., Utumi, M. and
Tomikawa, M. 2001. Dolphin-assisted seawater therapy for severe atopic dermatitis: an
immunological and psychological study. Archives of Allergy and Immunology 124: 389
390.
Kazdin, A. E. 1994. Methodology, design, and evaluation in psychotherapy research. In
Handbook of Psychotherapy and Behavior Change (4th ed.), 19–71, ed. A. E. Bergin and
S. L. Garfield. New York: Wiley.
Kazdin, A. E. and Wilson, G. T. 1978. Evaluation of behavior therapy: Issues, evidence
and research strategies. Cambridge, Massachusetts: Ballinger.
Kendall, P.C. and Norton-Ford, J.D. 1982. Therapy outcome research methods. In
Handbook of Research Methods in Clinical Psychology, 429-460, ed. P.C. Kendall and
J. N. Butcher, New York: John Wiley and Sons.
Lukina, L.N. 1999. Influence of dolphin-assisted therapy sessions on the functional state
26
of children with psychoneurological symptoms of diseases. Human Physiology 25: 676
679.
Marino, L. and Lilienfeld, S. O. 1998. Dolphin-assisted therapy: flawed data, flawed
Conclusions. Anthrozoos 11: 194-200.
Nathanson, D.E. 1998. Long-term effectiveness of dolphin-assisted therapy for children
with severe disabilities. Anthrozoos, 11: 22-32.
Nathanson, D.E., de Castro, D., Friend, H., and McMahon, M. 1997. Effectiveness of
short-term dolphin-assisted therapy for children with severe disabilities. Anthrozoos, 10:
90-100.
Samuels, A. and Spradlin, T. 1995. Quantitative behavioral study of bottlenose dolphins
in swim-with-the-dolphin programs in the United States. Marine Mammal Science11:
520-544.Servais, V. 1999. Some comments on context embodiment in zootherapy: the
case of the autodolfijn project. Anthrozoos 12: 5-15.
Shadish, W.R., Cook, T.D. and Campbell, D.T. 2002. Experimental and quasi
experimental designs for generalized causal inference. Boston: Houghton: Mifflin.
Shaughnessy, J. J. and Zechmeister, E. B. 1994. Research Methods in Psychology. New
York: McGraw-Hill.
27
Webb, N. L. and Drummond, P. D. 2001. The effect of swimming with dolphins on
human well-being and anxiety. Anthrozoos 14: 81-85.
Webster, L. S., Neil, D. T., and Madden, C. A. 1998. "Dolphin-initiated inter- and intra-
specific contact and aggression during provisioning at Tangalooma." Special Topic
report, Department of Geographical Sciences and Planning and School of Marine
Science, The University of Queensland.
Whale and Dolphin Conservation Society. 2006. Dolphin therapy in the headlines.
http://www.wdcs.org.au
Table 1. Major Threats to Validity in each of the five studies
Validity threat Definition Antonioli Iikura Webb and
and Reveley et al. Lukina Servais Drummond
(2005) (2001) (1999) (1999) (2001)___
Construct Validity
Nonspecific Effects (Improvement from
effects not specific to the intended treatment)
Placebo Improvement from X X X X X
expectation of
improvement
Novelty Effects of energy, X X X X X
excitement, and
enthusiasm not
specific to the
intended treatment
Construct Failure to take into X X X X X
Confounding account the fact that
the procedure may
include more than
one active ingredient
Resentful Participants aware X
Demoralization of not receiving the
active treatment may
be resentful and
respond more
negatively than the
treatment group
Demand Tendency of X X X
Characteristics participants to alter
their responses in
accord with their
suspicions about the
research hypothesis
Experimenter Tendency for X X X
Expectancy experimenter to
Effects unintentionally bias
the results in
accordance with
the hypothesis
Internal Validity
History Occurrence of X X
potentially therapeutic
events other than the
intended treatment
during the course
of the study
Testing Improvements due X X
to testing itself (e.g.,
practice effects)
Regression Tendency of X X
extreme scores to
become less
extreme on
re-testing
Instrumentation Changes in the X X
dependent measure
at different times in
the study
Multiple Administration of X X
Intervention treatments other
Interference than the intended
treatment during
the course of the
study
Maturation Changes over X X
time due to natural
developmental
effects
Informant bias Tendency of X X
informants to
selectively recall
improvement in
accord with their
hopes and
expectations
(retrospective
bias) or unintentional
distortion of
improvement due
to effort justification
