Handedness patterns may point to brain differences
Approximately ninety percent of the population is right- handed. Two new studies, however, suggest
unusually high rates of non-right-handedness in psychopaths and sex offenders.
An increase in non-right-handedness among offenders could indicate that disruptions in brain
development, leading to either left-hemisphere dysfunction or decreased asymmetry between the two
brain hemispheres, are common in these individuals. This would be consistent with earlier research
suggesting that psychopaths show abnormal patterns of brain asymmetry
(see related article, Crime Times, 1999, Vol. 5, No. 4, Page 3).
In one of the new studies, A. F. Bogaert analyzed a database of more than 8,000 men compiled by
the Kinsey Institute, and found that criminals in general and sex offenders in particular showed a
significantly higher rate of left-handedness or ambidexterity than did non-offenders. While there was
some evidence that handedness was linked to poor school performance in the criminal group, Bogaert
says, "education was unrelated to the handedness/pedophilia relationship." However, the effects of
handedness were small, and Bogaert cautions that "non-right-handedness should not be used as a
marker of criminality."
In a separate study, A. R. Mayer and D. S. Kosson investigated the hand preferences of 420 adult
male inmates in a county jail. "Psychopaths reported reduced right-hand dominance," they report, "which
cannot be accounted for by differences in age, intelligence, or race." They conclude that their data
suggest "anomalous cerebral asymmetry" in psychopathic offenders.
"Handedness, criminality, and sexual offending," A. F. Bogaert, Neuropsychologia, Vol.
39, No. 5, 2001, pp. 465-469. Address: A. F. Bogaert, Community Health Sciences, Brock
University, L2S 3A1, St. Catharine's, Canada.
** and **
"Handedness and psychopathy," A. R. Mayer and D. S. Kosson, Neuropsychiatry, Neuropsychology,
and Behavioral Neurology, Vol. 13, No. 4, October 2000, pp. 233-238. Address: A. R. Mayer,
Finch University of Health Sciences, Chicago Medical School, North Chicago, IL 60064.