ABSTRACT 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 and 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: DAT, dolphin-assisted therapy, dolphins, therapy, validity

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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, typically in captivity. DAT formally began in the 1970s 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 1970s 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 (Kazdin and Wilson 1978; Cook and Campbell 1979; Kendall and Norton-Ford 1982; Shaughnessy and Zechmeister 1994). We found no fewer than eleven independent methodological weaknesses in both studies that seriously undermined 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...