Erin J. Shumlich; Department of Psychology, Western University, London, Ontario, Canada
Graham, J. Reid; Department of Psychology, Western University, London, Ontario, Canada; Department of Family Medicine, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada; Department of Paediatrics, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada; Children’s Health Research Institute, London, Ontario, Canada
Megan Hancock; Alberta Children’s Hospital, Calgary, Alberta, Canada
Peter N.S. Hoaken, Department of Family Medicine, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada

Background: Robust executive function (EF) deficits have been found in criminal groups and have been implicated as contributors to criminal behavior. A widely cited model of EF is made up of inhibition, shifting, and working memory. The current study compares these three EF components of two different criminal groups to one another and to a normative sample.
Methods: EF of 42 forensic psychiatric patients was assessed and compared with 77 correctional offenders. EF was determined using the Delis-Kaplan Executive Function System (D-KEFS).
Results: Forensic psychiatric patients display poorer performance on EF compared to correctional offenders. Overall, forensic psychiatric patients perform most poorly on measures of shifting. Furthermore, a large proportion of both forensic psychiatric patients (9.5–35.7%) and correctional offenders (5.2–27.3%) display clinically significant deficits in all components of EF compared to what would be expected in the normative population (2.5%).
Conclusions/Implications: This study provides evidence of heterogeneity of cognitive deficits among different criminal populations and pervasive EF deficits in forensic and correctional populations compared to a normative sample. Understanding the unique EF profiles of different criminal groups can better inform rehabilitation programs and risk and release decisions.

Criminal; executive function; inhibition; shifting; working memory

“Crime is incredibly costly for society, the victim, and the perpetrator… Understanding the unique factors that lead individuals to commit crime, with or without the influence of a severe mental disorder, is essential in order to effectively rehabilitate offenders and to inform risk and release decisions. Furthermore, distinguishing between forensic psychiatric patients and correctional offenders may offer insight about the factors, beyond mental illness, that lead individuals to commit crime. The relationship between antisocial behaviors and both cognitive function and intelligence has received considerable attention in the past decade. Specifically, higher-order cognitive functions-or executive functions (EF)-have been implicated in criminal behavior…The current research is the first of its kind to compare EF deficits in forensic psychiatric patients and correctional offenders…” (p.243).

“…the current study utilized one of the most widely-accepted models of EF, Miyake at al.’s (2000) three-factor model of EF…they determined that EF is made up of (a) inhibition, (b) shifting, and (c) working memory. Other commonly discussed EF domains include purposive action, goal setting, abstract reasoning, prioritizing actions and goals, etc.…the first objective for the current study was to examine EF differences between a forensic psychiatric population and a correctional population. One concern is the overlap between EF and intelligence. Thus, EF was compared between forensic psychiatric patients and correctional offenders controlling for intelligence. It is hypothesized that the presence of a mental disorder in addition to criminal behavior may contribute to more significant EF deficits in forensic psychiatric patients compared to correctional offenders…independent of intelligence” (p.244-246).

“…the second objective was to explore specific aspects of inhibition, shifting, and working memory that may differ between forensic psychiatric patients and correctional offenders…It is hypothesized that some, but not all, aspects of inhibition, shifting, and working memory will differ between forensic psychiatric patients and correctional offenders; however, these analyses are exploratory…the third objective was to compare EF of forensic psychiatric and correctional populations with a normative sample. It is hypothesized that both forensic psychiatric and correctional populations will have poorer EF than a normative population. Participants for the current study were 42 adult male forensic psychiatric patients and 77 male correctional offenders from a previous study…exclusion criteria for correctional offenders included the presence of a mental disorder” (p.246).

“Forensic psychiatric patients display more severe deficits than correctional offenders in some measures of inhibition, shifting, and working memory. Both forensic psychiatric patients and correctional offenders demonstrated a wide range of EF deficits compared to the normative population. Specifically, a significantly higher proportion of forensic psychiatric patients (9.5-35.7%) and correctional offenders (5.2-27.3%) performed 2 SD below the mean compared to what would be expected in the normative population (2.5%). This suggests that both criminal populations are characterized by executive dysfunction, which is consistent with previous research. Further, forensic psychiatric patients scored more poorly on verbal intelligence than correctional offenders, which may have implications for scores on executive functioning measures” (p.252).

“Forensic psychiatric patients performed more poorly than correctional offenders on two CWIT [Color-Word Interference Test] tasks that measure inhibition…and a higher number of forensic psychiatric patients had clinically significant impairment on these measures compared to correctional offenders…Alternatively, correctional offenders had significantly lower scores than forensic psychiatric patients on 1 out of 9 measures of inhibition…Despite this, the proportions of both populations in the clinically significant range are not significantly different than would be expected in the general population, suggesting that these populations do not display clinical deficits overall in this measure” (p.252-253).

“Overall, forensic psychiatric patients had lower scores than correctional offenders on 2 out of 3 shifting measures…these results consistently show that forensic psychiatric patients are more deficit in shifting than correctional offenders…As with inhibition, the presence of severe mental disorders characteristic of forensic psychiatric populations…likely contribute to the more pervasive deficits in shifting in forensic psychiatric patients. A higher proportion of forensic psychiatric patients and correctional offenders displayed clinically significant deficits compared to the normative population in all three measures of cognitive shifting…Inability to shift relates to ruminative thinking…and could result in the escalation of violent and aggressive behavior due to the inability to shift from appropriate behavior to appropriate behavior…At the very least, the results of the current study provide a basis for future research looking at the role of shifting in criminal behavior” (p.253).

“Forensic psychiatric patients had significantly lower scores overall than correctional offenders on 3 out of 8 working memory measures…In addition to criminal behavior, the presence of a mental disorder and medication should be considered in future research as potentially contributing to working memory deficits…Our results are consistent with previous research suggesting that individuals with both a criminal history…and mental disorder…perform more poorly on measures of working memory (e.g., card sorting tasks). Interestingly, the proportion of both offender populations in the clinical range on the TT [Tower Test]-Achievement Score was not significantly different from the normed population…However, these results should be interpreted with caution since there is evidence to suggest that different tower tests tap into different components of EF…In terms of verbal fluency measures of working memory, forensic psychiatric patients were clinically impaired in 3 out of 6 measures and correctional offenders were clinically impaired in 5 out of 6 measures of verbal fluency. Impaired verbal fluency is a robust risk factor of criminal behavior…and may predict recidivism” (p.253-254).

“…First, the goal of the forensic psychiatric system is to rehabilitate and reintegrate offenders back into society, thus, it may be particularly important to treat EF difficulties. By understanding the unique EF factors associated with criminal behavior, there is the potential to develop rehabilitation programs that specifically target the functional needs of offenders based on the criminal group to which they belong…the need for rehabilitation programs that target offenders’ specific needs cannot be understated…EF could also be utilized in risk assessments. Predicting the likelihood that someone will engage in future criminal behavior is essential…The current research provides fodder for future investigation into the role of executive dysfunction in violence and aggression which may have implications in risk and release decisions” (p.254-255).

“The current study provides avenues for future research. The role of verbal intelligence in executive functioning differences should be explored in future research. The current research explored only cognitive tasks or the ‘cold’ aspects of executive functions…Likely, affective and motivational components of executive function influence criminal behavior, particularly related to violent, aggressive and antisocial behavior, and psychopathy…Therefore, future research should look at hot and cold executive function differences in various criminal subgroups. Future research should use a control group to compare these criminal groups with a matched non-offender group. Additionally, future research should compare the forensic psychiatric population with the civil psychiatric population in order to determine unique executive dysfunction in individuals with mental disorders who commit crime. Given the evidence to suggest that EF can be improved…future research should determine the impact of EF rehabilitation programs that specifically target offenders’ unique needs” (p.255-256).

“…Working memory has been implicated in the development and maintenance of schizophrenia…Furthermore, antipsychotic medication may negatively influence working memory…which may contribute to forensic psychiatric patients’ poorer performance on some working memory measures. Alternatively, there is some evidence to suggest that newer generations of antipsychotic medication may actually improve working memory…or have no effect on working memory…which may account for similar scores on the majority of working memory tasks…” (p.254).