Lesleigh Pullman and colleagues recently set out to assess the hypothesis that psychopathy might not be a mental disorder, but rather an effective life strategy. To do so, they analyzed a surprising sign of mental disorders: handedness.
Psychopathy is characterized by emotional and interpersonal deficits such as callousness, grandiosity, and a lack of empathy and remorse. It sometimes involves deviant behavior like aggression and violence.
The meta-analysis of more than 1,800 people failed to link psychopathy with handedness. This supports the hypothesis that psychopathy is an adaptive life strategy passed down through genes thanks to evolution, and not a mental disorder resulting from neurodevelopmental perturbations.
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Taken alone, however, these findings are not especially convincing, for a few reasons. First, the data did show some patterns suggesting that people higher in psychopathy may be more likely to be non-right-handed. But, the sample size may have been too small to detect real differences.
Moreover, psychopaths had about the same rates of non-right-handedness as incarcerated inmates and mental health patients. But if psychopathy is never a mental disorder, we would expect psychopaths to have lower rates of non-right-handedness than these groups (since these groups probably have more mental health disorders, and thus higher rates of non-right-handedness, than the general population).
