Psychopathy across cultures: North America and Scotland compared.

Differences in the prevalence and presentation of psychopathic personality disorder between North America and Scotland were evaluated. R. D. Hare's (1991) Psychopathy Checklist--Revised ratings obtained from a sample of 2,067 North American male prisoners and forensic patients were compared with ratings obtained from 246 Scottish male prisoners. Item response theory methods were used to examine differences in the performance of items and to equate the scale across settings. The items had equal relevance to the description of psychopathic personality disorder in both settings; however, the Scottish prisoners had to have higher levels of the underlying latent trait before certain characteristics became apparent. The prevalence of the disorder appears to be lower in Scotland. Explanations for the observed differences in terms of enculturation, socialization, and migration are explored.