Popout Effect in Eyewitness Identification

The “popout” effect refers to the subjective experience of witnesses who report virtually immediate or apparently automatic recognition of the perpetrator of a crime from a photo array or lineup. Researchers have detected this experience among witnesses by asking them to endorse one of several statements about the decision strategy they used when making their decision about a simultaneous lineup. In some (though not all) studies, witnesses who were accurate more frequently endorsed statements such as “I just recognized him, I cannot say why” and “His face just popped out at me” (automatic processing) than did inaccurate witnesses. The latter more often endorsed items such as “I compared the faces with one other to narrow the choices” and “I first eliminated the ones that were definitely not him, then chose among the rest” (deliberative processing). The popout effect has been of interest to eyewitness researchers and is relevant to the criminal justice system because such subjective reports could potentially be used as an indication of whether or not an identification decision is likely to have been accurate.

Evidence for the popout effect comes almost exclusively from examination of the relationship between identification accuracy and the characteristics of the subjective reports described above. While eyewitness researchers might well consider popout to be intuitively plausible, the reliance on retrospective reports to validate the effect is problematic. Indeed, it has been suggested that the demands associated with providing such retrospective reports might lead witnesses who have a very strong memorial image of the offender (and hence find it relatively easy to detect a match or an absence of a match in a lineup) to endorse items suggesting the occurrence of popout regardless of the actual characteristics of their search or decision processes.

Moreover, the view that reports of popout most likely imply an accurate identification is challenged by the finding that witnesses who misidentified a very similar looking but innocent foil from a simultaneous lineup were as likely to report popout as witnesses who accurately identified the perpetrator. This again points to the unreliability of subjective reports of the decision process as indicators of identification accuracy. Moreover, researchers have also shown that witnesses may be more likely to endorse the statement that the perpetrators’ face “popped out” at them and that they “just recognized him, I don’t know why” if they had been told that they picked the suspect from the lineup (when the perpetrator was in fact not present in the lineup), even though such feedback following the identification cannot have affected the actual decision process. There may be other factors that influence the extent to which popout is reported retrospectively, such as the typicality (in comparison with the broader population) of the face, the size of the array, and the location of the target in the array.

Despite these problems with validating the popout phenomenon, it is at least not inconsistent with data from studies in which the time taken to make the identification decision, identification response latency, has been examined. These studies show that accurate identification responses are, on average, significantly faster than inaccurate responses. Furthermore, there is at least some evidence that participants who endorsed more items suggestive of automatic processing tended to be those who made faster identifications, whereas those who endorsed more deliberative processing items tended to be slower.

The popout effect has been distinguished from another type of decision process, an absolute decision strategy, on the ground that an absolute decision strategy does not predict shorter decision latencies whereas popout does. The reason for shorter decision latencies when popout occurs is that the examination of the lineup may cease after the face has popped out of the array. In contrast, an absolute decision strategy is characterized by witnesses comparing the members of the lineup with their memory of the perpetrator, with this occurring for each member of a simultaneous lineup array. Other behavioral data, such as eye movement recordings, have not, as yet, been investigated to provide converging evidence for the popout effect, but they could help validate the effect. If popout occurs, it would be expected that witnesses would engage in very little scanning of the members of the lineup, fixating quickly on the lineup member that pops out. This eye movement pattern should differ from both an absolute judgment strategy, where each lineup member should be fixated but overt comparisons between lineup members should not be detected, and a relative judgment strategy, where eye movements should indicate comparisons between the various lineup members.

It is worth noting that basic research in the area of visual search points to a phenomenon that appears to parallel the popout experience attributed to some witnesses when viewing a photo array. The popout effect in the visual search paradigm appears to derive from an early, “preattentive” registration of the key features of a stimulus during parallel processing of the full stimulus array, with this leading to rapid termination of the search of the stimulus array.

In sum, the popout effect has been argued to occur on the basis of witnesses’ subjective reports of the decision strategy used to make an identification decision and the time taken to make the decision. It is important because it could potentially be helpful in distinguishing accurate from inaccurate identification decisions. However, the reliance on retrospective reports to demonstrate the phenomenon is problematic, with future research needing to be directed at identifying behavioral measures of popout.

References:

  1. Brewer, N., Gordon, M., & Bond, N. (2000). Effect of photoarray exposure duration on eyewitness identification accuracy and processing strategy. Psychology, Crime & Law, 6, 21-32.
  2. Dunning, D., & Stern, L. B. (1994). Distinguishing accurate from inaccurate eyewitness identifications via inquiries about decision processes. Journal of Personality and Social Psychology, 67, 818-835.
  3. Ross, D. F., Rapus Benton, T., McDonnell, S., Metzger, R., & Silver, C. (2007). When accurate and inaccurate eyewitnesses look the same: A limitation of the “pop-out” effect and the 10- to 12-second rule. Applied Cognitive Psychology, 21(5), 677-690.
  4. Weber, N., Brewer, N., Wells, G. L., Semmler, C., & Keast, A. (2004). Eyewitness identification accuracy and response latency: The unruly 10-12 second rule. Journal ofExperimental Psychology: Applied, 10, 139-147.
  5. Wells, G. L., Olson, E. A., & Charman, S. D. (2003). Distorted retrospective eyewitness reports as functions of feedback and delay. Journal of Experimental Psychology: Applied, 9, 42-52.

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