Are the Mentally Retarded and Learning Disordered Overrepresented Among Sex Offenders and Paraphilics?

Abstract

A sample of 2,286 male sex offenders and paraphilics and 241 nonsex offenders was evaluated for the prevalence of mental retardation and learning disorders, using the full Wechsler IQ scales. The sex offenders were generally of average intelligence, and the mentally retarded were not overrepresented among them, but the learning disordered were. There were no differences among sex offenders and controls in overall IQ or in the percentage of mentally retarded or learning-disordered cases, suggesting that the learning difficulties are not peculiar to sex offenders. There was a bias in referral source, with more mentally retarded, borderline-retarded, and/or learning-disordered cases being referred by the Children's Aid Society, prisons, and the Crown, suggesting that referral source may play a significant role in evaluating intelligence and mental retardation among sex offenders; but the overrepresentation of learning disorders among criminals appears to be a significant phenomenon, regardless of referral source.

The Neuropsychology of Sex Offenders

“…Several typologies have been proposed to distinguish subgroups(e.g., Marshall, Laws, & Barbaree, 1990; Prentky, Knight, Rosenberg, & Lee, 1989). Surprisingly, neuropsychological studies have tended to ignore these typologies and to group subtypes of sex offenders and/or subtypes of cognitive measures (merging together pedophilic child molesters and rapists of adults, for instance, or using composite scores of neuropsychological batteries; e.g., Flor-Henry, 1987; Langevin & Curnoe, 2008a; Langevin, Wortzman, Wright, & Handy, 1988; Spinella, White, Frank, & Schiraldi, 2006; Young, Justice, & Edberg, 2010). This approach has yielded the classic neurobiological hypothesis of sexual deviance, which attributes a prominent role to fronto-temporal anomalies, especially in the left hemisphere (e.g., Flor-Henry, 1987; Gillespie & McKenzie, 2000; Lang, 1993; O’Carroll, 1989).…”

The relationship between lower intelligence, crime and custodial outcomes: a brief literary review of a vulnerable group

“…This is also the case with the different forms and categories of below average functioning (e.g. cognitive deficits, impairment, borderline) and it is noted that this issue is particularly complex given that individuals of average intelligence can still have specific learning deficits (Langevin & Curnoe, 2008).…”

“…It may also not be as strong as once thought (Herrero et al, 2010;Langevin & Curnoe, 2008). One of the primary difficulties in resolving this issue is that intelligence is now accepted to involve a range of different cognitive processes, not least performance and verbal intelligence.…”

“…cognitively impaired group) in the prison population compared to the general population (Ho, 1996). Researchers have suggested that this is because this group are more likely to be careless in avoiding detection due to their cognitive impairments (Langevin & Curnoe, 2008). Researchers have also suggested that the appropriate identification of lower IQ offenders is usually ignored during the initial stages such as police interviews (Noble & Conley, 1992).…”

Psychiatric and Forensic Differences Between Men Charged with Sex Offences and Men Charged with Other Offences

“…As expected, in forensic NGRI populations, the prevalence is much higher than in individuals convicted of sexual offences sent for a forensic assessment. Also, a significant proportion of individuals convicted of sexual offences are of borderline or lower intelligence; however, some claim that people with intellectual disabilities are not overrepresented among people suspected of sexual offences (13).…”