Vol. 10, No. 2, 2004 Page 1
Psychopaths are callous, glib, superficial, and impulsive; lack empathy for others; and display no guilt or remorse for their harmful acts. One reason for these traits, research suggests, is that psychopaths have difficulty understanding emotions. However, a new study indicates that psychopaths are impaired not just in the emotional realm, but more broadly, in understanding abstract information in general.
Kent Kiehl, Robert Hare, and colleagues studied eight male criminal psychopaths, all inmates of a maximum-security prison in Canada, comparing them to eight non-criminal, non-psychopathic controls. The researchers controlled for a wide range of factors including age, parental socioeconomic status, education level, and IQ.
The subjects participated in a test in which they viewed concrete words (such as "table"), abstract words (such as "justice"), and pseudo- words. All words were selected to be emotionally neutral to eliminate emotional response as a factor. Subjects viewed word groups containing either concrete words and similar-looking pseudo-words, or abstract words and similar-looking pseudo-words. They were instructed to raise one hand each time a real word appeared, and to raise the other hand if a pseudo-word appeared. During the tests, the researchers investigated brain changes in the participants using functional magnetic resonance imaging (fMRI).
Psychopathic subjects, Kiehl et al. say, "performed more poorly, manifested as slower reaction times, than control participants, when processing abstract word stimuli." This is consistent, they say, with studies showing that psychopaths have trouble processing abstract words, performing abstract categorization tasks, understanding metaphors, and processing emotionally weighted words and speech.
In particular, the psychopaths showed clear deficits in activating one brain area, the right anterior superior temporal gyrus, when processing abstract stimuli. This region failed to differentiate normally between abstract and concrete stimuli.
The researchers say, "These data support the hypothesis that there is an abnormality in the function of the right anterior superior temporal gyrus in psychopathy."
"Perhaps," the researchers say, "psychopathic individuals have difficulty engaging in cognitive functions that involve material that has no concrete realization in the external world. We might speculate that complex social emotions such as love, empathy, guilt and remorse may be a form of more abstract functioning. Thus, difficulties in processing and integrating these conceptually abstract representations to regulate or modulate behavior would be [seen] in these individuals."
"Temporal lobe abnormalities in semantic processing by criminal psychopaths as revealed by functional magnetic resonance imaging," Kent A. Kiehl, Andra M. Smith, Adrianna Mendrek, Bruce B. Forster, Robert D. Hare, and Peter F. Liddle, Psychiatry Research: Neuroimaging, Vol. 130, 2004, 27-42. Address: Kent A. Kiehl, kent.kiehl@yale.edu.