Crime and Personality

Eysenck argues that conformity to social rules is normally secured by a system of aversions acquired through associative conditioning in early childhood. When a child pilfers and is punished, the act becomes paired with anxiety; this conditioned response generalizes, creating what is commonly called conscience . The mechanism is powerful precisely because it is irrational: ordinary people avoid crime not from fear of apprehension—detection rates are too low for that to be rational—but from the resurgence of anxiety that accompanied similar actions in the past . Criminality results when this conditioning process fails, either because the individual is constitutionally unresponsive to conditioning or because socialization arrangements were inadequate .

Eysenck links conditionability to his two major personality dimensions. Extraverts condition poorly, and neurotics condition poorly; the most criminal personality therefore has the highest extraversion-neuroticism score . The reasoning is physiological: extraverts have lower cortical arousal and therefore require stronger or more frequent reinforcement to form conditioned associations. Since socialization proceeds by partial reinforcement—irregular pairing of misdeed and sanction—extraverts are disadvantaged in acquiring the anxiety responses that constitute conscience . Eysenck acknowledged one exception: individuals reared by criminal parents may show high introversion scores because they have been conditioned to antisocial rather than prosocial values .

The book reviews twin studies, adoption studies, and cross-cultural comparisons. Eysenck argued that identical twins show higher concordance for criminality than fraternal twins, and that adopted children's criminality correlates more with biological than adoptive parents . He also compared criminals in Western and Communist countries, claiming that offenders behind the Iron Curtain showed the same personality characteristics as those in the West—an argument designed to refute purely political or environmental explanations . A contemporary reviewer noted that Eysenck's conclusion 'that criminality is inherited requires more evidence than he presents,' and that more recent studies did not reach the same conclusion .

A review in The Eugenics Review identified several weaknesses. Eysenck equated conditioning with socialization, but the terms are not interchangeable; the theory struggles to explain white-collar crime, which is practiced by highly socialized individuals . The book's data relied heavily on imprisoned offenders, who represent a small and unrepresentative fraction of all criminals—fewer than 20 percent of those convicted are imprisoned . The theory also cannot explain the 8:1 male-to-female crime ratio, since introversion-extraversion is normally distributed in both sexes . A reviewer in Crime & Delinquency noted that Eysenck's genetic conclusions rested on 'dated studies' and that his later environmental attributions introduced inconsistency .

Crime and Personality was first published in 1964 by Routledge & Kegan Paul in London, and by Houghton Mifflin in Boston . The original edition ran 204 pages. A third edition, 'completely revised and brought up to date,' was published in 1977 by Routledge & Kegan Paul, running 222 pages . Although the major theory linking personality and crime was retained, many details changed in conformity with research at the time . The book was reissued in Routledge's 'Psychology Revivals' series in 2013 . A German translation, Kriminalität und Persönlichkeit, appeared in 1977 .

A 2006 article in the journal History of the Human Sciences noted that even those who vehemently rejected Eysenck's theory acknowledged Crime and Personality as 'the most highly articulated and influential biological explanation of crime of its time' . Yet the same article observed that Eysenck's name was 'fading from criminological memory—and none too soon, in the opinion of critics who continue to anathematize him as a self-serving showman, charlatan, and dangerous right-wing conservative' . A 1989 analysis from the Office of Justice Programs described Eysenck as 'a pioneer in modern biological criminology' whose theories were criticized on theoretical, philosophical, and ethical grounds, with some labeling him racist and fascist .