In this chapter, we report our own systematic review. We divide studies into categories: full scale IQ scores, measures of verbal ability, performance intelligence, deviation scores (PIQ—VIQ), executive functioning, and myriad cognitive abilities. We also separate studies of the following categories of executive functioning: memory, planning, problem solving, attention, and cognitive control (a.k.a. cognitive impulsivity).Tests that were difficult to categorize into one particular skill, such as those that combine executive skills, and tests of set switching or maintenance, tests that were not used often, such as visual organization and reaction time, were combined into an additional category of “other" measures of executive function. In addition, there were studies which used tests of higher cognitive abilities that seemed to combine skills, and these were put into a general “other cognitive abilities” category. These included strategy scores, the Stockings of Cambridge test, and the WAIS comprehension subtest.
A search of the Criminal Justice Abstracts and PsycINFO databases was conducted. We combined search terms related to potential independent variables with a list of outcome terms when narrowing the search was necessary. In Criminal Justice Abstracts, the outcome terms were: aggression, delinquency, crime, violence, violent, property, theft, status, nonviolent, and non-violent. In PsychInfo, the outcome terms were aggression, delinquency, crime, violence, violent, property, theft, status, aggression, conduct disorder, conduct problems, externalizing, behavioral problems, antisocial, and nonviolent.
For the independent variables, we used a set of initial search terms that were broad-attempting to capture educational, intellectual, executive, and learning measures. We later added more specific terms, such as test names, which turned up in our original set of returns. The final set of search terms was: education, educational, attainment, academic, school, grades, intelligence, intellectual, verbal, Wechsler, IQ, PIQ, WAIS, Stanford-Binet, PIQ, deviation score, language, learning disability, dyslexia, minimal brain dysfunction, cognitive, executive, neuropsychological, memory, planning, problem solving, cognitive, language, reading, SILS abstraction, continuous performance, CPT, Digit Symbol, NEPSY visual, planning, Porteus, Tower, mazes, cognitive control, dichotic listening, go-no-go (and go no go), attention shifting, time estimation, response inhibition, distracta- bility, color word, CWIT, failure to maintain set, cognitive switching, set switching, Stroop, response control, digit span, visual retention, A not B, conditional association, number randomization, self-ordered pointing, block design, Trail Making, TMT, design fluency, sorting test, perceptual organization, picture completion, picture arrangement, visual organization, visual perception, Paced Auditory Serial
Addition Test, paired associates, CAT-ASVAB, Stockings of Cambridge, perfect solutions, excess moves, WISC comprehension, object assembly, ALTUC, and Booklet Category.
In this chapter, we included all studies of intellectual ability and measures and their association with physical aggression/violence, or with nonviolent- only offending (mainly theft and other property crime; not including drug-only offending). The master list was culled for “tier 1” items which we deemed had the highest likelihood of reporting associations between intelligence or education factors and violence. We categorized approximately 30 publications as tier 1 items. We also evaluated a long list of “tier 2” items (approximately 380), the titles of which are ambiguously related to our focus, suggesting either that they are studies of risk factors for violence (and we cannot tell if they measure intellectual abilities), or studies of education or intelligence and “crime” or delinquency (where we cannot tell if they measure violence). A few other studies were also evaluated as we became aware of them, most commonly as we were reading and coding for other chapters. Because electronic searches are incomplete, and our “sampling” is directed toward obtaining every published study, we included items that we discovered in reference lists as well. Over 100 studies and almost 900 comparisons were added to our full table.