Studies show that psychopaths' brains respond in abnormal ways to facial emotion
Converging lines of evidence suggest that psychopathy involves impairment of the amygdala, which plays a central role in processing emotions. In particular, studies hint that in psychopaths, this brain structure reacts abnormally to vocal or facial expressions of emotion-a finding supported by two new studies.
The first study, by Quinton Deeley and colleagues, compared psychopathic men to normal males. Deeley and colleagues asked six men diagnosed as psychopathic, and nine men who served as controls, to view images of faces exhibiting happiness, fear, or a neutral expression while undergoing functional magnetic resonance imaging (fMRI). All of the psychopaths were repeat criminal offenders, with records including attempted murder, manslaughter, rape, and other forms of violent assault.
The researchers asked participants to identify whether the faces they viewed were male or female, but the experiment actually focused on how the men responded to the emotional content of the pictures. The researchers found that:
"In healthy people, visual cortical activation in response to fearful faces is boosted by feedback modulation from the amygdala," the researchers say. "Hence, reduced rather than increased visual cortical response to fearful faces compared with neutral faces in psychopathy may reflect differences in amygdala function in people with this disorder.
- In normal males, as expected, both happy and fearful faces provoked a greater response than neutral faces in brain areas known to be involved in facial analysis (the fusiform and extrastriate cortices).
- These areas were less active in psychopaths than in controls when the men viewed happy faces, but the psychopaths' response, while diminished, showed a normal pattern.
- Psychopaths, however, reacted very differently from controls when looking at fearful faces. While normal males showed a greater response to fearful faces than neutral ones, psychopaths actually exhibited less reaction in the fusiform gyrus.
This would support suggestions that amygdala dysfunction underpins selective deficits in processing facial expressions of distress in adults with psychopathy and children with psychopathic traits, including recognition of fearful and sad faces, and reduced autonomic responsiveness to distress cues."
In most people, a fearful response from another person is aversive-in other words, it acts much like a "punishment"-and this natural response conditions us not to harm others. "Failure to recognize and emotionally respond to facial and other signals of distress," Deeley and colleagues say, "may underlie failure to inhibit behavior that engenders distress in others during social interaction or, more generally, may underlie the lack of emotional empathy observed in this population."
In a related study, Mairead Dolan and Rachael Fullam compared 49 male criminals with antisocial personality disorder to 49 non-criminal men matched for IQ. The researchers measured the subjects' ability to recognize facial expressions, and found that the antisocial group showed deficits in recognizing sad and happy emotions, even when photos expressed the emotions vividly. The deficits did not stem from impulsive responding, because the antisocial group took longer to recognize all of the tested emotions (anger, disgust, fear, happiness, sadness, and surprise) than did control subjects.
Moreover, the researchers found that within the antisocial group, those with the highest scores for psychopathy were significantly worse at recognizing sadness than antisocial subjects who did not meet the definition of psychopathy. (While the two disorders are similar, less than 20% of people with antisocial personality disorder meet the criteria for psychopathy.) However, the psychopaths did not have difficulty recognizing happy faces.
The researchers say their findings suggest that due to amygdala deficits, antisocial individuals (and psychopaths in particular) fail to associate expressions of sadness and fear with their actions, leading to poor socialization.
"Facial emotion processing in criminal psychopathy," Q. Deeley, E. Daley, S. Surguladze, N. Tunstall, G. Mezey, D. Beer, A. Ambikapathy, D. Robertson, V. Giampietro, M. J. Brammer, A. Clarke, J. Dowsett, T. Fahy, M. L. Phillips, and D. G. Murphy, British Journal of Psychiatry, Vol. 189, 2006, 533-39. Address: Declan Murphy, D.Murphy@iop.kcl.ac.uk.
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"Face affect recognition deficits in personality-disordered offenders: association with psychopathy," Mairead Dolan and Rachael Fullam, Psychological Medicine, Vol. 36, 2006, 1563-69. Address: firstname.lastname@example.org.