School of Psychology, University of Birmingham, Birmingham B15 2TT, United Kingdom.
Department of Psychology, University of California San Diego, La Jolla, CA 92093.
Proc Natl Acad Sci U S A. 2021 Feb 23;118(8). doi: 10.1073/pnas.2017292118.
A typical police lineup contains a photo of one suspect (who is innocent in a target-absent lineup and guilty in a target-present lineup) plus photos of five or more fillers who are known to be innocent. To create a fair lineup in which the suspect does not stand out, two filler selection methods are commonly used. In the first, fillers are selected if they are similar in appearance to the suspect. In the second, fillers are selected if they possess facial features included in the witness's description of the culprit (e.g., "20-y-old white male"). The police sometimes use a combination of the two methods by selecting description-matched fillers whose appearance is also similar to that of the suspect in the lineup. Decades of research on which approach is better remains unsettled. Here, we tested a counterintuitive prediction made by a formal model based on signal detection theory: From a pool of acceptable description-matched photos, selecting fillers whose appearance is otherwise dissimilar to the suspect should increase the hit rate without affecting the false-alarm rate (increasing discriminability). In Experiment 1, we confirmed this prediction using a standard mock-crime paradigm. In Experiment 2, the effect on discriminability was reversed (as also predicted by the model) when fillers were matched on similarity to the perpetrator in both target-present and target-absent lineups. These findings suggest that signal-detection theory offers a useful theoretical framework for understanding eyewitness identification decisions made from a police lineup.
一个典型的警察列队包含一张嫌疑犯的照片（在没有目标的列队中是无辜的，在有目标的列队中是有罪的），加上五张或更多的填充者的照片，这些填充者已知是无辜的。为了创建一个公平的列队，使嫌疑犯不突出，通常使用两种填充者选择方法。在第一种方法中，如果填充者与嫌疑犯外貌相似，则选择他们。在第二种方法中，如果填充者具有证人对罪犯描述中包含的面部特征（例如，“20 岁白人男性”），则选择他们。警方有时会结合这两种方法，选择描述相符且外貌与列队中的嫌疑犯相似的填充者。几十年来，哪种方法更好的研究仍未解决。在这里，我们测试了一个基于信号检测理论的正式模型提出的反直觉预测：从可接受的描述相符的照片中选择与嫌疑犯外貌不同的填充者，应该会在不影响虚报率（提高辨别力）的情况下提高命中率。在实验 1 中，我们使用标准的模拟犯罪范式证实了这一预测。在实验 2 中，当填充者在有目标和无目标列队中都与犯罪者的相似性相匹配时，对辨别力的影响被反转（这也与模型预测一致）。这些发现表明，信号检测理论为理解从警察列队中做出的目击者识别决策提供了一个有用的理论框架。
