Intelligence and criminal behavior in a total birth cohort: An examination of functional form, dimensions of intelligence, and the nature of offending

Intelligence has been found to predict a wide range of criminal and antisocial behaviors, including violent and chronic offending. The results from this literature have shown that individuals with lower intelligence levels (typically measured as IQ) tend to be more likely to engage in criminal behavior. Despite the pervasiveness of this basic finding, many aspects of the IQ-offending relationship remain unclear, such as the functional form of the association. Some perspectives expect a discrete or curvilinear association, while others assume a more incremental or linear pattern. The current study contributes to this literature by examining the functional form of the IQ-offending association in a total birth cohort of Finnish males born in 1987. Criminal offending was measured with nine different indicators from official records and intelligence was measured using three subscales (verbal, mathematical, and spatial reasoning) as well as a composite measure. The results show consistent evidence of mostly linear patterns, with some indication of curvilinear associations at the very lowest and the very highest ranges of intellectual ability. We discuss the implications of these findings for future research.