Weapon-Focus Effect

Laboratory studies find reduced identification accuracy when a weapon is present, and eye-tracking shows fixation on it. Whether the cause is arousal or simply that a weapon is an unexpected object in the scene is unresolved, and the distinction matters for whether the effect generalises to witnesses who expected the weapon.

In practice

• A witness who describes the knife in detail and the hand holding it vaguely is exhibiting the pattern.
• An investigator weighting a confident facial identification from an armed robbery is weighting the weakest condition.

Possible explanations

Explanations divide between arousal, in which threat narrows attention onto its source, and unusualness, in which any unexpected object in the scene draws fixation. Eye-tracking supports attentional capture without settling which property causes it.

In its favour

Laboratory studies find reduced identification accuracy when a weapon is present, and the fixation pattern is directly observable rather than inferred.

Against it

Meta-analytic effects are modest, the mechanism remains disputed, and effects in real crimes appear smaller than in the laboratory, where the scene is brief and stripped of context.

Standing

Meta-analytic effects are modest and the mechanism is disputed between attentional capture by threat and by unusualness. Effects in real crimes appear smaller than in the laboratory.

Subject

Psychology & Behavior

Essay

A century and a half of measuring the mind