The weapon focus effect is the tendency for witnesses who observe an armed criminal to direct their attention toward the weapon so that they fail to encode and remember information about the perpetrator’s physical appearance as accurately as they would have if no weapon had been visible. This effect can have important consequences for the investigation of a crime, as the police often rely on witnesses’ descriptions of a perpetrator as they attempt to identify a suspect.
In lab experiments investigating weapon focus, researchers typically expose participant-witnesses to slide sequences, videos, or live enactments in which a target person holds a weapon (in the experimental condition) or a neutral object (in the control condition), although sometimes in the control condition the target is empty-handed. Several kinds of weapons have produced the effect, including a handgun, carving knife, switchblade knife, meat cleaver, liquor bottle, and syringe. Usually witnesses’ performance in a condition with a completely visible weapon is compared with performance in a condition with no weapon, but in some studies researchers have manipulated the amount of exposure time or the degree of visibility.
The primary dependent variable, witnesses’ memory of the target’s appearance, has been measured using two different methods. First, witnesses may attempt to describe the target’s physical features (e.g., height, hair color) and clothing by responding to open-ended or multiple-choice questions. Many studies have demonstrated that a weapon’s presence impairs the accuracy of witnesses’ descriptions. A second method is to ask witnesses to identify the target in a lineup. The weapon’s influence on this less sensitive measure is weaker, with a few experiments reporting null results.
Although memory of the target’s appearance is the main interest in most studies, a weapon’s presence can harm the ability to remember other aspects of the target as well. For example, witnesses exposed to a weapon may find it more difficult than controls to recall the semantic content of verbal statements made by the target.
If witnesses in the experimental condition focus on the weapon to a greater extent than controls focus on the neutral object, one might expect this difference to be revealed by eye movements and by memory for the object. Consistent with these expectations, researchers found that witnesses made more frequent and longer eye fixations on an object held by a target in a slide sequence if that object was a gun rather than a non-weapon. Additionally, although only a few studies have investigated memory for the object, those that do exist generally indicate that witnesses can identify and describe a weapon better than a neutral object.
Some researchers have used field studies rather than lab experiments to explore the weapon focus effect, usually by interviewing witnesses to actual crimes or examining police reports. Some, though not all, of these investigations have yielded null results. Perhaps these findings are at odds with those obtained in lab experiments because field studies are more realistic. Alternatively, the discrepancy could be attributed to field researchers’ difficulty in surmounting daunting methodological obstacles. For example, determining the accuracy of witnesses’ reports is problematic because there is often no complete, objective record of the scene they observed. Also, researchers must struggle to eliminate potential confounds with the weapon’s presence, such as exposure time, retention interval, the witness’s vantage point, the perpetrator’s behavior, and differences in police response (e.g., the police might question witnesses to crimes involving weapons more thoroughly than witnesses to weaponless crimes). Nevertheless, field studies are a valuable complement to lab research, and they offer the possibility of greater ecological validity.
Two different explanations for the weapon focus effect have been discussed in the literature. The first interprets it as a consequence of the psychological arousal or anxiety that the sight of a weapon is supposed to create. The idea is that as a witness’s anxiety rises to a point above the optimal level, attentional capacity shrinks so that the witness focuses mostly on central cues (e.g., the weapon, because it is the source of the anxiety) at the expense of peripheral cues (e.g., the perpetrator’s clothing and facial features). This hypothesis is contradicted by several findings: Memory of the target is not affected by (a) the level of threat that the armed target directs toward another person, (b) the degree of threat associated with the object held by the target, or (c) having a confederate holding a syringe threaten the witnesses by telling them that they would receive an injection as part of the experiment. Moreover, the weapon focus effect occurs even when witnesses rate their anxiety as low.
An alternative explanation proposes that weapons seem unusual or unexpected within many contexts. Furthermore, it is known that unusual objects within visual scenes attract attention. Consistent with this account, research has shown that an unusual object, such as a stalk of celery or a toy Pillsbury doughboy, can have the same impact on memory of the target as a weapon.
One prediction that follows from the unusualness explanation is that a weapon should fail to elicit the typical weapon focus effect if it appears within a context in which weapons would be expected. For example, a gun held by a target at a shooting range would not be out of place. A test of this prediction revealed that, as hypothesized, a weapon focus effect did not occur in that setting.
An interesting question with both theoretical and practical implications concerns the mechanism by which weapons attract attention. Specifically, do weapons capture attention automatically? If so, witnesses would have relatively little awareness of and control over their attentional focus. However, if the answer is no, potential witnesses (e.g., bank tellers and convenience-store workers) could perhaps receive training that educates them about the weapon focus effect and teaches them to watch the perpetrator rather than the weapon as a crime unfolds. Recent data suggest that educated witnesses can overcome the weapon focus effect, which implies that weapons probably do not capture attention automatically.
References:
- Loftus, E. F., Loftus, G. R., & Messo, J. (1987). Some facts about “weapon focus.” Law and Human Behavior, 11(1), 55-62.
- Pickel, K. L. (1999). The influence of context on the “weapon focus” effect. Law and Human Behavior, 23(3), 299-311.
- Steblay, N. M. (1992). A meta-analytic review of the weapon focus effect. Law and Human Behavior, 16(4), 413-124.
Return to the overview of Eyewitness Memory in Forensic Psychology.