THE SOCIOBIOLOGY OF SOCIOPATHY: AN INTEGRATED EVOLUTIONARY MODEL
Department of Psychology
College of St. Benedict
St. Joseph, MN 56374
sociobiology, sociopathy, psychopathy, antisocial personality, evolution, criminal behavior, game theory, emotion, moral development, facultative strategies
Sociopaths are "outstanding" members of society in two senses: politically, they command attention because of the inordinate amount of crime they commit, and psychologically, they elicit fascination because most of us cannot fathom the cold, detached way they repeatedly harm and manipulate others. Proximate explanations from behavior genetics, child development, personality theory, learning theory, and social psychology describe a complex interaction of genetic and physiological risk factors with demographic and micro-environmental variables that predispose a portion of the population to chronic antisocial behavior. Recent evolutionary and game theoretic models have tried to present an ultimate explanation of sociopathy as the expression of a frequency-dependent life history strategy which is selected, in dynamic equilibrium, in response to certain varying environmental circumstances. This target article tries to integrate the proximate, developmental models with the ultimate, evolutionary ones. Two developmentally different etiologies of sociopathy emerge from two different evolutionary mechanisms. Social strategies for minimizing the incidence of sociopathic behavior in modern society should consider the two different etiologies and the factors which contribute to them.
Sociopaths, who comprise only 3-4% of the male population and less than 1% of the female population (Strauss & Lahey 1984, Davison and Neale 1994, Robins, Tipp & Przybeck 1991), are thought to account for approximately 20% of the United States' prison population (Hare 1993) and between 33% and 80% of the population of chronic criminal offenders (Mednick, Kirkegaard-Sorensen, Hutchings, Knop, Rosenberg & Schulsinger 1977, Hare 1980, Harpending & Sobus 1987). Furthermore, whereas the "typical" U.S. burglar is estimated to have committed a median five crimes per year before being apprehended, chronic offenders- those most likely to be sociopaths- report committing upward of fifty crimes per annum and sometimes as many as two or three hundred (Blumstein & Cohen 1987). Collectively, these individuals are thought to account for over 50% of all crimes in the U.S. (Loeber 1982; Mednick, Gabrielli & Hutchings 1987, Hare 1993).
Whether criminal or not, sociopaths typically exhibit what is generally considered to be irresponsible and unreliable behavior; their attributes include egocentrism, an inability to form lasting personal commitments and a marked degree of impulsivity. Underlying a superficial veneer of sociability and charm, sociopaths are characterized by a deficit of the social emotions (love, shame, guilt, empathy, and remorse). On the other hand, they are not intellectually handicapped, and are often able to deceive and manipulate others through elaborate scams and ruses including fraud, bigamy, embezzlement, and other crimes which rely on the trust and cooperation of others. The sociopath is "aware of the discrepancy between his behavior and societal expectations, but he seems to be neither guided by the possibility of such a discrepancy, nor disturbed by its occurrence" (Widom 1976a, p 614). This cold- hearted and selfish approach to human interaction at one time garnered for sociopathy the moniker "moral insanity" (McCord 1983, Davison & Neale 1990).
Sociopaths are also sometimes known as psychopaths or antisocial personalities. Unfortunately, the literature reflects varied uses of these three terms (Hare 1970, Feldman 1977, McCord 1983, Wolf 1987, Eysenck 1987). Some authors use one or another term as a categorical label, as in psychiatric diagnosis or in defining distinct personality "types"; an example is the "antisocial personality" disorder described in the Diagnostic and Statistical Manual of the American Psychiatric Association (1987). Other authors use the terms to refer to individuals who exhibit, to a large degree, a set of behaviors or personality attributes which are found in a continuous, normal distribution among the population at large; an example of such usage is "sociopathy" as defined by high scores on all three scales of the Eysenck Personality Questionnaire- extraversion, neuroticism, and psychoticism (Eysenck 1977, 1987).
Other authors make a distinction between "simple" and "hostile" (Allen, Lindner, Goldman & Dinitz 1971), or "primary" and "secondary" psychopaths or sociopaths (Fagan & Lira 1980), reserving the term "simple" or "primary" for those individuals characterized by a complete lack of the social emotions; individuals who exhibit antisocial behavior in the absence of this emotional deficit are called "hostile" or "secondary" psychopaths or sociopaths, or even "pseudopsychopaths" (McCord 1983). Other authors also make a typological distinction, using the term "psychopath" to refer to anti-social individuals who are of relatively high intelligence and middle to upper socio-economic status and who express their aberrant behavior in impressive and sometimes socially skilled behavior which may or may not be criminal, such as insider trading on the stock market (e.g. Bartol 1984). These authors reserve the term "sociopath" for those antisocial persons who have relatively low intelligence and social skills or who come from the lower socio- economic stratum and express their antisocial nature in the repeated commission of violent crime or crimes of property.
I will begin by using the single term "sociopath" inclusively. However, by the end of the paper I hope to convince the reader that the distinction between primary and secondary sociopaths is an important one because there are two different etiological paths to sociopathy, with differing implications for prevention and treatment.
My basic premise is that sociopaths are designed for the successful execution of social deception and that they are the product of evolutionary pressures which, through a complex interaction of environmental and genetic factors, lead some individuals to pursue a life history strategy of manipulative and predatory social interactions. On the basis of game theoretic models this strategy is to be expected in the population at relatively low frequencies in a demographic pattern consistent with what we see in contemporary societies. It is also expected to appear preferentially under certain social, environmental, and developmental circumstances which I hope to delineate.
In an effort to present an integrated model, I will use a variety of arguments and data from the literature in sociobiology, game theory, behavior genetics, child psychology, personality theory, learning theory, and social psychology. I will argue that: (1) there is a genetic predisposition underlying sociopathy which is normally distributed in the population; (2) as the result of selection to fill a small, frequency-dependent, evolutionary niche, a small, fixed percentage of individuals- those at the extreme of this continuum- will be deemed "morally insane" in any culture; (3) a variable percentage of individuals who are less extreme on the continuum will sometimes, in response to environmental conditions during their early development, pursue a life-history strategy that is similar to that of their "morally insane" colleagues; and (4) a subclinical manifestation of this underlying genetic continuum is evident in many of us, becoming apparent only at those times when immediate environmental circumstances make an antisocial strategy more profitable than a prosocial one.