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Beware the Dodo Bird: The Dangers of Overgeneralization


Address correspondence to Dianne L. Chambless, Department of Psychology, Room 207, Davie Hall, Cameron Avenue, UNC-CH, Chapel Hill, NC 27599–3270. E-mail:


Luborsky et al.'s conclusion that there are no meaningful differences in the efficacy of various psychothera-pies should be reconsidered for the following reasons: (a) errors in data analysis, (b) exclusion of research on many types of clients (e.g., children and adolescents), (c) faulty generalization to comparisons between therapies that have never been made, and (d) erroneous assumption that the average difference between all sorts of treatments for all sorts of problems can be assumed to represent the difference between any two types of treatment for a given problem. Concern for clients' welfare demands that psychologists be very wary of accepting the Dodo bird verdict.