The Dodo Bird Verdict Is Alive and Well—Mostly
Version of Record online: 11 MAY 2006
Clinical Psychology: Science and Practice
Volume 9, Issue 1, pages 2–12, March 2002
How to Cite
Luborsky, L., Rosenthal, R., Diguer, L., Andrusyna, T. P., Berman, J. S., Levitt, J. T., Seligman, D. A. and Krause, E. D. (2002), The Dodo Bird Verdict Is Alive and Well—Mostly. Clinical Psychology: Science and Practice, 9: 2–12. doi: 10.1093/clipsy.9.1.2
- Issue online: 11 MAY 2006
- Version of Record online: 11 MAY 2006
- Received August 22, 2000; revised January 17, 2001; accepted January 30, 2001.
- comparisons of active psychotherapies;
- psychotherapy outcomes;
- correction for researcher's treatment allegiances;
- empirically validated treatments;
- Dodo bird verdict
We examined 17 meta-analyses of comparisons of active treatments with each other, in contrast to the more usual comparisons of active treatments with controls. These meta-analyses yielded a mean uncorrected absolute effect size for Cohen's d of .20, which is small and non-significant (an equivalent Pearson's r would be. 10). The smallness of this effect size confirms Rosenzweig's supposition in 1936 about the likely results of such comparisons. In the present sample, when such differences were corrected for the therapeutic allegiance of the researchers involved in comparing the different psychotherapies, these differences tend to become even further reduced in size and significance, as shown previously by Luborsky, Diguer, Seligman, et al. (1999).