Attention-shifting impairment seen in violent offenders

Violent offenders show significant deficits in attentional "set-shifting" when compared to normal or mentally disabled controls, according to a new study by A. H. Bergvall and colleagues.

The researchers say the violent offenders were not impaired on tasks measuring working memory and planning. However, they showed marked impairment on a task requiring them to focus their attention on one visual dimension (e.g., shapes as opposed to lines), then switch their attention to a newly-relevant dimension, and then switch their attention back to the first relevant stimulus. On this task, Bergvall et al. say, "the violent offenders committed on average three times as many errors as the controls," performing worse than either normal or mentally retarded controls.

"At the heart of the deficit," they say, "is the loss of inhibitory cognitive control, expressed as an impairment of shifting attention from one perceptual dimension to another and as a blunted ability to alter behavior in response to fluctuations in the emotional significance of stimuli." They speculate that this defect may stem from impairment of prefrontal cortex functions, which are strongly implicated in criminal behavior.

The researchers note that many of the subjects in the violent offender group had childhood histories of problems related to hyperactivity, poor attention, and/or aggression-conditions that today would be diagnosed as attention deficit hyperactivity disorder, developmental coordination disorder, or conduct disorder. "Because these developmental conditions can persist into adulthood, constitute risk factors for adult criminality, and entail executive dysfunction," they say, "it is quite possible that the cognitive deficits we note in the present study constitute adult forms of these developmental psychopathologies."

"A deficit in attentional set-shifting of violent offenders," A. H. Bergvall, H. Wessely, A. Forsman, and S. Hansen, Psychological Medicine, Vol. 31, August 2001, 1095-1105. Address: S. Hansen, Department of Psychology, Göteborg University, Box 500, SE 405 30 Göteborg, Sweden.