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Psychopathology (alternatively psychopathy, or sociopathy), is a group of traits typically associated with impulsiveness, aggressive or anti-social behavior, and a characteristic lack of emotion. According to Cleckley (1941, pg.90):
- It is impossible for [the psychopath] to take even a slight interest in the tragedy or joy or the striving of humanity as presented in serious literature or art. He is also indifferent to all these matters in life itself. Beauty and ugliness, except in a very superficial sense, goodness, evil, love, horror, and humour have no actual meaning, no power to move him.
This emotional "color-blindness" is also coupled with a social presense often described as "charming" or "seductive". Psychopaths are adept manipulators, able and willing to "manage impressions" (to use Hare's term) to their own ends. To illustrate, Hare describes one man in a research study at the prison he was employed in at the time. The man was administered a personality test, the Minnesota Multiphasic Personality Inventory (MMPI), used to diagnose the disorder, on three seperate occasions. In each case, he was able to fool the test, and the clinical psychologist administering it, that he was, respectively, psychotic, normal, and mildly disturbed. It later came to light that he had deceived the doctors to first be transfered to a mental health facility, secondly, to be transfered back to the general prison facility, and the final time, to secure a supply of Valium (Hare, 1993). While this example may be amusing and relatively harmless, many psychopaths, like the infamious serial killer Ted Bundy, employed their "talents" towards more nefarious ends.
With this in mind, Mealey (1995) proposed a frequency-dependent evolutionary model of psychopathy. Unlike altruists, who reciprocate cooperative behaviors, psychopaths exploit it, feigning cooperation and subsequently defecting. According to Mealey, this is one way in which men with lower status, little resources and little prospect for attaining either, can compete with others in a traditional hierarchy (to understand the importance of this, see human mating strategies and sexual preferences). The disorder would be cued in the presense of certain environmental triggers, including the absense of a father, low socio-economic status, and a large number of siblings.
However, the phenotype can only be maintained at certain levels. When there are too many psychopaths in the population, costs to cooperators would be sufficently high to presumably warrent the evolution of counter-strategies. Additionally, psychopaths would also have to worry about frequent contact with other psychopaths. On the other hand, levels too low could never be maintained in the population.
Mealey's hypothesis, while intriguing, still has a long way to go. Some tentative support has been provided by Willerman et al (1992), who found that psychopathy is moderatly heritable, but its still unclear if the levels required to be maintained in a population are high enough, and the absense of studies outside Western populations is a serious deficiency.