The relationship between intellectual ability and the treatment needs of offenders in a therapeutic community prison

Abstract

This study explores the relationship between intellectual ability (IA) and the treatment needs of male offenders in a therapeutic community prison. A sample of 1627 offenders with varying levels of IA as measured using the Raven's Progressive Matrices (RPM; Raven, 1958) were compared on psychometric measures assessing offence-related treatment needs. A multivariate analysis of variance (MANOVA) revealed that offenders with a lower level of IA had significantly higher scores on particular scales of the Hostility and Direction of Hostility Questionnaire (HDHQ; Caine, Foulds, & Hope, 1967), the Psychological Inventory of Criminal Thinking Styles (PICTS; Walters, 1995) and the Blame Attribution Inventory (BAI; Gudjonsson, 1984), and a multivariate analysis of covariance (MANCOVA) found that these differences persisted even after controlling for social desirability. Findings suggest that offenders with a lower level of IA may require adapted treatment interventions that target differences in treatment need.

Keywords:

• intellectual ability
• criminal thinking
• offender interventions
• male offenders

Notes

1. Pitman and Ireland (2003) referred to ID rather than IA.

2. It is important to make this point because although a number of findings relating to ID offenders are likely to apply to offenders with very low IA, IA and ID are not synonymous. We do, however, discuss research involving ‘ID’ populations because offenders are often selected on the basis of a low score on an intelligence test rather than meeting the criteria for ID. The British Psychological Society, American Psychological Association, American Association for Intellectual and Development Disabilities and World Health Organisation require three criteria to be met in order for an individual to be classified as having an intellectual disability: (i) an IQ or standard score two deviations below the mean; (ii) significant deficits in adaptive behaviour and (iii) onset of a disability during childhood (Lindsay & Taylor, 2008).

3. All applicants to Grendon are vetted to ensure that they have at least 18 months of their sentence left to serve, and prisoners sign a contract to indicate their motivation to stay in treatment for at least this period of time.

4. There was a significant difference between the RPM grades on these two scales at the p < .05 level, although when a Bonferroni correction was applied to reduce the likelihood of a Type-I error, this difference was no longer significant.