Wechsler performance IQ greater than Verbal IQ index in a forensic sample: a reconsideration.

Abstract

Explored the relationships of the Performance IQ (PIQ) greater than Verbal IQ (VIQ) to type of crime, ethnicity, and reading disability in a corrections sample of 70 adult males incarcerated on felony charges. The PIQ greater than VIQ sign was not related to Full Scale IQ or to violent vs. nonviolent crime, per se. The PIQ greater than VIQ sign showed a trend toward association with Ethnicity (black vs. white) and was related significantly to reading disability, with the reading disabled inmates more likely to show the sign, and to type of crime, with perpetrators of sex crimes most likely (87%) to show the sign and those incarcerated for murder or attempted murder least likely (33%) to show it. The difference in the proportion of inmates who showed the sign in these two classes of violent crimes (murder and sex crimes) was significant, and further analysis showed that with murder excluded, PIQ greater than VIQ occurred significantly more frequently in those accused of violent crimes than for nonviolent crimes. The latter findings suggested that differences between studies in the relationship of PIQ greater than VIQ and violence may be the result of differences in the proportion of murderers in the violent samples. Additional analyses indicated that the significant relationships between PIQ greater than VIQ and both type of crime and reading disability were most likely independent of ethnicity and each other.