Lester Luborsky

Lester Luborsky is a psychotherapy reasearcher.

Following an extensive meta-analyses of psychotherapy outcome studies Luborsky (2002) showed that the effect size that can be attributed to specific therapy techniques is only 0.2. Therefore, all therapies are to considered equal and "all must have prizes".

This finding has been taken to support Saul Rosenzweig (1936) who coined the phrase the "Dodo bird verdict", and has been extensively referred to in subsequent literature as a consequence of the 'common factor' theory. This is the theory that the specific techniques that are applied in different types and schools of psychotherapy serve a very limited purpose (such as a shared myth to believe in), and that most of the positive effect that is gained from psychotherapy is due to factors that the schools have in common, namely the therapeutic effect of having a relationship with a therapist who is warm, respectful and friendly.