Stimulus characteristics that can enhance or decrease aggression: Associations with prior positive or negative reinforcements for aggression

To establish an analogue of the “weapons effect,” male university subjects were required to use a distinctive apparatus in delivering noxious sounds to a peer in an adjoining room, and then were either (a) positively reinforced, or (b) negatively reinforced, or (c) not given any reaction by the experimenter, for what they had done. Immediately after this, each person had to administer other noise blasts to someone else in a different manner, but with the previous noise machines (the fist “weapon”) being either present or not present. The initial “weapon's” presence augmented the effects of the prior reinforcement; the second victim was attacked most strongly after the men had been positively reinforced and the earlier “weapon” was nearby, whereas he received the fewest blasts if the subjects had been negatively reinforced and the earlier noise machine was present. Other evidence indicates (1) that the aggressive cue, the “weapon,” had not affected the subjects' aggressive intentions, (2) the results are not due simply to differences in moods or general arousal, and (3) the subjects were not aware of the hypothesis regarding the interaction of reinforcement and cue presence.     

Longitudinal predictors of weapon involvement in middle adolescence: Evidence from the UK Millennium Cohort Study

This study uses longitudinal data from the UK Millennium Cohort Study (N = 13,277) to examine the childhood and early adolescence factors that predict weapon involvement in middle adolescence, which in this study is exemplified by having carried or used a weapon. It finds that childhood experiences of low family income and domestic abuse between parents predict weapon involvement at age 17 years. Other predictors include childhood externalizing problems and self-harm in early adolescence. Further early adolescent behaviors and experiences that predict weapon involvement are own substance use, peer substance use, school exclusion, and high levels of electronic gaming. These findings provide concrete areas for targeting risk factors both in childhood and the early adolescent period, with an indication that early intervention and prevention are likely to reduce the need for later action.     

The weapon focus effect is weaker with Black versus White male perpetrators

We compared the influence of a weapon’s presence on eyewitnesses’ memory for a White versus a Black male perpetrator. Prior data indicate that unusual objects in visual scenes attract attention and that a weapon’s effect depends on how unusual it seems within the context in which it appears. Therefore, given the stereotype linking Black men and weapons, we predicted a weaker weapon focus effect with the Black perpetrator. The results of Experiment 1 supported this hypothesis using White and Black witnesses. Moreover, in Experiment 2 the weapon focus effect became nonsignificant when the Black perpetrator wore a style of clothing that is strongly associated with Black men. We propose that observing an armed Black perpetrator automatically activates a stereotype linking Black men with weapons and crime, which in turn reduces the perceived unusualness of the weapon and thus its ability to attract attention.     

Eyewitness Memory for Typical and Atypical Weapons in Cognitive Context

The present research addressed eyewitness memory for weapons, specifically for a modern semi‐automatic pistol and an antique flintlock, in order to address the influence of weapon novelty on recall for the given weapon. Additionally, the effect of explanatory backstory was examined in the same context; respondents were given prior information, which was either consistent or inconsistent with the presence of the flintlock in the scene, in order to gauge the influence of appropriate or inappropriate explanatory cognitive context. Finally, the effects of these variables on line‐up identification of the ‘suspect’ holding the given weapon were addressed. The results showed that weapon type did not influence recall accuracy for given weapons, although explanatory backstory did have a significant effect here, as initially predicted. Both weapon type and explanatory backstory produced significant effects on weapon recall errors, with the exotic weapon and the more prosaic backstory producing larger numbers of mistakes. Neither of these variables was associated with significant differences in line‐up performance. These results indicate the importance of prior cognitive context, as well as the physical appearance of weapons, in a full understanding of eyewitness processing of scenes involving firearms. Copyright © 2013 John Wiley & Sons, Ltd.     

Weapon Bias: Split-Second Decisions and Unintended Stereotyping

ABSTRACT— Race stereotypes can lead people to claim to see a weapon where there is none. Split-second decisions magnify the bias by limiting people's ability to control responses. Such a bias could have important consequences for decision making by police officers and other authorities interacting with racial minorities. The bias requires no intentional racial animus, occurring even for those who are actively trying to avoid it. This research thus raises difficult questions about intent and responsibility for racially biased errors.     

Choice of Weapon or Weapon of Choice? Examining the Interactions between Victim Characteristics in Single‐victim Male Sexual Homicide Offenders

As most studies report that the majority of sexual homicide offenders (SHOs) prefer to kill with their own hands, research has largely neglected to examine the choice of weapon by these offenders. The US Supplementary Homicide Reports show that although a large number of SHOs murder their victim using personal weapons (e.g. bare hands and manual or ligature strangulation), the majority use an alternative weapon (e.g. edged weapons, contact weapons, and firearms). The present study hypothesises that the choice of weapon is in part influenced by victim characteristics. To identify specific combinations and interactions between victim characteristics and the choice of a personal or edged weapon during the commission of a sexual homicide, a combination of exhaustive chi‐square automatic interaction detector and conjunctive analysis is used on a sample of 2,472 single‐victim male SHOs from a 36‐year period of Supplementary Homicide Report data (1976–2011). Findings show that SHOs choose their weapon according to some victim characteristics. Implications of the findings are discussed in light of police suspect prioritisation. Copyright © 2014 John Wiley & Sons, Ltd.     

The influence of alcohol and weapon presence on eyewitness memory and confidence

In this quasi-experimental field study, bar drinkers (0.00–0.23% blood alcohol content) viewed a photographic sequence in which a male took a laptop from a helpdesk assistant, either on loan or at gunpoint. Following a brief retention period, participants answered 20 multiple-choice questions about the male, his actions, and details of the scene, then attempted to identify him from a simultaneous target-present or target-absent line-up. Alcohol was associated with a reduction in correct identifications and an increase in false identifications. Surprisingly, the presence of a weapon in the scene enhanced identification accuracy, though wider scene memory was not influenced by alcohol or the weapon. Findings offer some support for the view that alcohol restricts face encoding, perhaps through the narrowing of attention to salient external features (e.g., hair). We also suggest that curiosity about mock-crime perpetrators may produce weapon focus reversals, although the factors that might elicit such curiosity remain unclear.     

Understanding the weapon focus effect: The role of threat,unusualness, exposure duration,and scene complexity

We examined the role of exposure duration and scene complexity on the weapon focus effect (WFE). Memory for the mock crime was affected more by a weapon than an unusual but nonthreatening object. Threat reduced correct identifications when the event was short but not long; duration of the event did not interact with unusualness. Additionally, we found a WFE for target‐absent lineup decisions, but only for the accomplice lineup, not the object‐wielding perpetrator's lineup. We discuss the implications of these results for illuminating the mechanisms that elicit the WFE.