Forgetting the once-seen face: estimating the strength of an eyewitness's memory representation.

The fidelity of an eyewitness's memory representation is an issue of paramount forensic concern. Psychological science has been unable to offer more than vague generalities concerning the relation of retention interval to memory trace strength for the once-seen face. A meta-analysis of 53 facial memory studies produced a highly reliable association (r=.18, d=0.37) between longer retention intervals and positive forgetting of once-seen faces, an effect equally strong for both face recognition and eyewitness identification studies. W. A. Wickelgren's (1974, 1975, 1977) theory of recognition memory provided statistically satisfactory fits to 11 different empirical forgetting functions. Applied to the results of field studies of eyewitness memory, the theory yields predictions relevant to fact finders' evaluations of eyewitness credibility. A plausible upper limit for witness initial memory strength corresponds to a probability of .67 of being correct on a fair six-person lineup. Furthermore, not only can the percentage of remaining memory strength be determined for any retention interval, but this strength estimate can be translated into an estimated probability of being correct on a fair lineup of a specified size.

Mugshot exposure effects: Retroactive interference, mugshot commitment, source confusion, and unconscious transference.

More than 25 years of research has accumulated concerning the possible biasing effects of mugshot exposure to eyewitnesses. Two separate metaanalyses were conducted on 32 independent tests of the hypothesis that prior mugshot exposure decreases witness accuracy at a subsequent lineup. Mugshot exposure both significantly decreased proportion correct and increased the false alarm rate, the effect being greater on false alarms. A mugshot commitment effect, arising from the identification of someone in a mugshot, was a substantial moderator of both these effects. Simple retroactive interference, where the target person is not included among mugshots and no one in a mugshot is present in the subsequent lineup, did not significantly impair target identification. A third metaanalysis was conducted on 19 independent tests of the hypothesis that failure of memory for facial source or context results in transference errors. The effect size was more than twice as large for "transference" studies involving mugshot exposure in proximate temporal context with the target than for "bystander" studies with no subsequent mugshot exposure.

A meta-analytic review of the effects of high stress on eyewitness memory.

In the past 30 years researchers have examined the impact of heightened stress on the fidelity of eyewitness memory. Meta-analyses were conducted on 27 independent tests of the effects of heightened stress on eyewitness identification of the perpetrator or target person and separately on 36 tests of eyewitness recall of details associated with the crime. There was considerable support for the hypothesis that high levels of stress negatively impact both types of eyewitness memory. Meta-analytic Z-scores, whether unweighted or weighted by sample size, ranged from -5.40 to -6.44 (high stress condition-low stress condition). The overall effect sizes were -.31 for both proportion of correct identifications and accuracy of eyewitness recall. Effect sizes were notably larger for target-present than for target-absent lineups, for eyewitness identification studies than for face recognition studies and for eyewitness studies employing a staged crime than for eyewitness studies employing other means to induce stress.