In the first part of the talk, I will present experiments (Ahn, Proctor, & Flanagan, 2009, Cognitive Science) examining mental health clinicians’ beliefs about biological, psychological, and environmental bases of the DSM-IV-TR mental disorders, and the consequences of those causal beliefs for judging treatment effectiveness. Studies 1 and 2 found a large negative correlation between clinicians’ beliefs about biological bases and environmental / psychological bases. Study 3 further found that clinicians believe medication to be more effective for biologically-based mental disorders and psychotherapy to be more effective for psychosocially-based mental disorders. These results demonstrate that mental health clinicians make strong distinctions between psychological and biological phenomena.

In the second part of the talk, I will present studies examining the clinical utility of the Five Factor Model (FFM) of Personality, an assessment and classification system under consideration for integration into the forthcoming DSM-V. We investigated whether practicing clinicians (Rottman, Ahn, Sanislow, & Kim, 2009, American Journal of Psychiatry) and experts in personality pathology (Rottman, Kim, Ahn, & Sanislow, under review) were able to translate FFM patient descriptions into the corresponding diagnostic categories used in the DSM-IV. The results showed that both practicing clinicians and experts had considerable difficulty disambiguating the meaning of the dimensions to determine correct diagnoses. They also judged the utility of the FFM in devising treatment plans or making prognoses to be lower than the DSM. Implications for categorization and causal reasoning research will be discussed.