Gender Differences

If intellectual abilities are important in the etiology of violence, we might ask whether sex differences can be explained by differences in particular intellectual functions. Campbell (2006) looked at research on sex differences in EFs and found that “In general, sex differences appear to be absent, weak or inconsistent on EF tests” (p. 250). However, sex differences in verbal ability have been discussed for some time. Bennett et al. (2005), among others, emphasize verbal abilities as a potential key to understanding gender differences in crime and violence. They list a series of findings consistent with this assessment. Males perform less well than females on tests of verbal ability, especially speech production. Males frequently experience developmental lags in left hemisphere

Table 4.3 Summary of Study-Level Findings Related to Measures of Executive Functions and Violent vs. Nonviolent Offending

Summary of STUDY Results

Independent Variable Category

Number of Studies (k)

s

O

©

Ж

Memory

Violent Nonviolent Violent vs. Nonviolent

  • 11
  • 2
  • 10
  • 2
  • 0
  • 0
  • 3
  • 2
  • 2
  • 1
  • 0
  • 1
  • 4 0
  • 5
  • 1
  • 0
  • 2

Planning

Violent Nonviolent Violent vs. Nonviolent

  • 8
  • 1
  • 6
  • 1
  • 0
  • 1
  • 0
  • 0
  • 0
  • 0
  • 0
  • 0
  • 5
  • 1
  • 1
  • 2
  • 0
  • 4

Problem Solving

Violent Nonviolent Violent vs. Nonviolent

  • 6
  • 2
  • 10
  • 1
  • 0
  • 1
  • 1
  • 1
  • 1
  • 0
  • 1
  • 1
  • 2
  • 0
  • 2
  • 2
  • 0
  • 5

Attention

Violent Nonviolent Violent vs. Nonviolent

  • 10
  • 1
  • 4
  • 3
  • 0
  • 0
  • 1
  • 0
  • 1
  • 0
  • 0
  • 0
  • 6
  • 1
  • 2
  • 0
  • 0
  • 1

Cognitive Control (Cognitive Impulsivity)

Violent Nonviolent Violent vs. Nonviolent

  • 17
  • 3
  • 7
  • 3
  • 2
  • 0
  • 2
  • 1
  • 1
  • 0
  • 0
  • 1
  • 8
  • 0
  • 3
  • 4
  • 0
  • 2

Other Cognitive Tests

Violent Nonviolent Violent vs. Nonviolent

  • 10
  • 2
  • 10
  • 0
  • 0
  • 0
  • 1
  • 2
  • 3
  • 0
  • 0
  • 0
  • 5
  • 0
  • 2
  • 4 0
  • 5

Other Measures of Executive Functions

Violent Nonviolent Violent vs. Nonviolent

  • 19
  • 3
  • 16
  • 4
  • 1
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 9
  • 0
  • 9
  • 4
  • 0
  • 3

Щ Findings are ambiguous

О Findings are in the opposite direction of the attachment hypothesis (not necessarily statistically significant)

© Relationship is reported as “null” or coefficient = 0

• Findings are in the expected direction of the attachment hypothesis but are not statistically significant

X Findings are in the expected direction of the attachment hypothesis and are statistically significant

Table 4.4 Summary of Comparison-Level Findings Related to Measures of Executive Functions and Violent vs. Nonviolent Offending

Summary of COMPARISONS

Independent Variable Category

Number of Comparisons

О

©

X

Memory

Violent Nonviolent Violent vs. Nonviolent

  • 25
  • 4
  • 43
  • 8
  • 4
  • 8
  • 3
  • 0
  • 5
  • 7
  • 0
  • 19
  • 7
  • 0
  • 12

Planning

Violent Nonviolent Violent vs. Nonviolent

  • 15
  • 1
  • 8
  • 2
  • 0
  • 0
  • 0
  • 0
  • 1
  • 8
  • 1
  • 1
  • 5 0
  • 6

Problem Solving

Violent Nonviolent Violent vs. Nonviolent

  • 23
  • 10
  • 17
  • 5
  • 6 3
  • 0
  • 4
  • 2
  • 13
  • 0
  • 5
  • 5
  • 0
  • 7

Attention

Violent Nonviolent Violent vs. Nonviolent

  • 23
  • 3
  • 16
  • 7
  • 1
  • 5
  • 0
  • 0
  • 0
  • 13
  • 2
  • 4
  • 3
  • 0
  • 7

Cognitive Impulsivity

Violent Nonviolent Violent vs. Nonviolent

  • 89
  • 14
  • 24
  • 24
  • 7
  • 6
  • 3
  • 2
  • 1
  • 31
  • 5
  • 9
  • 31
  • 0
  • 8

Other Cognitive Tests

Violent Nonviolent Violent vs. Nonviolent

  • 32
  • 3
  • 20
  • 7 3
  • 8
  • 2
  • 0
  • 0
  • 8
  • 0
  • 2
  • 15
  • 0
  • 10

Other Measures of Executive Functions

Violent Nonviolent Violent vs. Nonviolent

  • 107
  • 15
  • 62
  • 22
  • 8
  • 13
  • 3
  • 3
  • 6
  • 51
  • 4
  • 26
  • 31
  • 0
  • 17

О Findings are in the opposite direction of the attachment hypothesis (not necessarily statistically significant)

© Relationship is reported as “null” or coefficient = 0

• Findings are in the expected direction of the attachment hypothesis but are not statistically significant

X Findings are in the expected direction of the attachment hypothesis and are statistically significant maturation, which may account for early lags in language development compared to females. Girls develop language skills faster than boys do and are better at encoding of nonverbal expressions. Unfortunately, in the studies we reviewed, males were not compared to females, so the answer to this question cannot be found here.

There is a subset of studies where the association between intelligence/EF and offending behavior was tested with girls, or disaggregated by sex. Such studies might tell us whether the intelligence-violence association holds for females as well as males. There were many studies of males, and fewer of females. In studies of overall intelligence and violence among females, there were an equal number of studies reporting a preponderance of findings in the right direction to the number in the wrong direction (k = 2). Even for verbal ability, the findings were very mixed. Only 3 out of 8 were in the expected direction, with 3 studies in the opposite direction, where violent females actually had higher verbal ability. In one of the ambiguous studies, the authors reported significant negative correlations between verbal ability and violence among females, but when they ran multivariate models, these associations were no longer statistically significant. There were very few studies examining the association between executive functioning and violence for females. Koda (1999) and Andrew (1982) report that violent females had higher scores on memory, attention, and cognitive control than comparison subjects; Raaijmakers et al. (2008) found the same for “other” measures of EF. Raaijmakers et al. (2008) found that memory and cognitive control were negatively associated with physical aggression for girls, but the relationships were not statistically significant. Yeomans (1996) found that violent female offenders had lower scores on memory, problem solving, cognitive control, EF, and other cognitive measures than nonviolent offenders. Thus, for females, the association between intelligence and EFs and violence is not nearly as clear as is the association for males. There is too little research comparing males to females to determine whether sex differences are due to differences in verbal ability.

 
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