Judging veracity impairs eyewitnesses' memory of a perpetrator.

Witnesses to crimes sometimes perform cognitively demanding tasks while simultaneously observing a perpetrator. This division of attentional resources can cause witnesses to remember the perpetrator less accurately. We hypothesised that judging the veracity of a target individual can impair subsequent memory for his or her appearance and message. In Experiment 1, we demonstrated that the veracity judgement task is cognitively demanding by having participants perform a concurrent secondary task. In three additional experiments, we confirmed that witnesses who judged the veracity of a target remembered his or her appearance and message less accurately than witnesses who simply observed the target. We also extended this result by showing that suspicion amplified the memory impairment effect, apparently by inducing witnesses to allocate even more resources to the judgement task (Experiments 2a and b), and that witnesses' memory was less accurate when they used a cue within the message content rather than a nonverbal cue to judge veracity (Experiment 3). Contrary to our prediction, however, witnesses who monitored two cues versus one did not display worse memory performance.