Verbal Ability and Violence
As we described in Chapter 2, low verbal intelligence has been emphasized in the literature on antisocial behavior and the mechanisms by which verbal ability is thought to affect antisocial behavior have also been discussed extensively. Because communication is an important part of social interaction, deficits in this area would be expected to disrupt the development and maintenance of normal social relationships.
Associations between verbal abilities, aggression, and violence have been found in people of all ages, from children as young as 19 months up through adolescents and adults (Dionne et al., 2003). Some authors characterize verbal abilities as one of the “most well-established neurocognitive impairments associated with conduct behavior problems” (Barker et al., 2007, p. 593) and those who have interviewed violent offenders have remarked that verbal skills are severely limited (e.g., Stein, 2007). The findings have been consistent across many studies. Giancola, Mezzich, and Tarter (1998) found that language skills were significantly, negatively related to all forms of antisocial behavior, controlling for age and socioeconomic status (SES), in their sample of young girls. In the Children in the Community study, verbal IQ scores were lowest among those on the persistent aggressive offense trajectory (Cohen et al., 2002). Dionne et al. (2003) found a significant correlation in their study of 19-month-old twins and Seguin et al. (2009) found it, controlling for other neurcognitive abilities. In the Cambridge study, low verbal ability predicted frequent involvement in group fights in boyhood (but not adult violence) (Farrington, 2003). Low verbal IQ was most common among violent offenders (45%)-much more common, even, than it was among frequent nonviolent offenders (29%) (Farrington, 1991).
There are some important exceptions and caveats, which require further scrutiny. These exceptions include a study by Raine, Yaralian, Reynolds, Venables, and Mednick (2002) who found that spatial but not verbal deficits predicted persistent offending. While Farrington (2003) reported some associations between verbal IQ and violence but concluded that low verbal intelligence at ages 8-10 was not among the best predictors of persistent offending in the Cambridge Study of Delinquent Development. The association was also absent in the Philadelphia portion of the Collaborative Perinatal Project, where verbal IQ was not associated with early onset offending, controlling for factors such as gender, low birth weight and family adversity (Gibson, Piquero, & Tibbetts, 2001). It was also not significant in a study by Bellair and McNulty (2005), who looked at the association between verbal ability and serious violence, using Add Health data.