PIQ > VIQ Intelligence Discrepancy

A note in an early manual of intelligence testing, to the effect that criminals are characterized by a high score on performance intelligence (PIQ) relative to verbal intelligence (VIQ), has apparently led to research on what is called the PIQ > VIQ discrepancy (Walsh, 1991). Walsh (1991) believed that the weight of the evidence was definitely supportive at the time of his writing and made the case that nonsupportive studies had low sample sizes, used data on less serious delinquents, and employed techniques that reduced statistical power. In his sample, Walsh found that 35.5% of his delinquent sample had PIQ > VIQ, when this proportion in a general population sample was 16%. In many reviews, authors emphasize deviation scores (e.g., Moffitt, 1997). Reviewers have concluded that serious delinquents differ from other children in that their PIQ is generally higher than their VIQ. In the studies Moffitt (1997) reviewed, delinquents’ PIQs were higher than their VIQs. Because language functions take place mainly in the left hemisphere of the cerebral cortex, the findings have been interpreted as evidence of dysfunction there. Thus, we will also scrutinize the literature on this topic to see if the PIQ > VIQ discrepancy is an important predictor of violent vs. nonviolent offending.

 
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