Left-hemisphere activation and deficient response modulation in psychopaths.

Psychopathic offenders have difficulty processing contextual or secondary cues once they have initiated goal-directed behavior or allocated attention to a primary task. To test the hypothesis that this deficit in response modulation is specific to conditions in which psychopaths' left-hemisphere resources are engaged, we administered a serial recall task to 21 incarcerated psychopaths and 21 control subjects. Subjects were instructed to memorize eight words that were presented one at a time, each in one of the four corners of the visual display. Subjects' primary task was to recall the words in serial order. Then, without forewarning, they were asked to recall the words' locations. As predicted, psychopaths performed as well as control subjects in recalling words from the left and right spatial fields, but recalled significantly fewer locations from the right spatial field. Thus, psychopaths' deficient response modulation was specific to conditions in which their left-hemisphere resources were actively engaged.