If you happen not to be a psychiatrist or a psychologist, you might reasonably imagine that mental health professionals have written many other books on this crucial and intriguing question: Can zeitgeist have an enduring negative effect on the individual psyche? But the startling fact is that most of the relevant scholarly writings by psychopathologists are quite new (post-2001), and discussions for nonprofessionals are rare. Over the past 40 years or so, psychology has attempted to divvy up the causes of pathological conditions between two now-famous categories, “nature” (as transmitted genetically) and “nurture” (environmental influences). For various psychopathologies, including paranoid schizophrenia, and also normal “personality traits” (introversion/extraversion, conservatism/liberalism, rigidity/adaptability, and several dozen more), research has yielded remarkably consistent results, indicating that these differences among human beings are accounted for by genetic and environmental factors in more or less equal measure, with genetics sometimes edging out environment by a point or two (51 versus 49 percent, in some instances). This research has been indispensable to our growing appreciation of the role of genetics both in normal personality and in the mental illnesses.

Contrastingly, our conception of environmental influences has been biased and narrow. We have tended to think of “nurture” only in the familial sense: In mental health research, “environment” tends to mean child-rearing factors, which is to say the personalities and actions of parents and, to a lesser degree, siblings. That an individual’s personality or mental illness might be affected by environmental factors outside the home has been largely overlooked. Take the study of sociopathy, which is another profound form of psychopathology—this one characterized not by delusions but by the complete absence of conscience. Research indicates that the factors involved in sociopathy, like those in many other mental illnesses, are about 50 percent genetic and 50 percent environmental. But researchers have been perplexed because they have been unable to find specific child-rearing variables that would consistently account for the environment’s half in cultivating sociopaths. I maintain (in my book The Sociopath Next Door) that this half consists primarily of larger societal factors, and this idea would seem to be supported by the fact that the incidence of diagnosed sociopathy is significantly lower in certain East Asian countries (most notably Taiwan and Japan) than in North America. It seems likely that, in the United States especially, any genetic predisposition to sociopathy will be nurtured and shaped by a single-mindedly competitive and individualistic culture that regards “winning” and domination as the ultimate goods.