Determinants of Face Recognition: The Role of Target Prevalence and Similarity.

Studies of facial identity processing typically assess perception (via matching) and/or memory (via recognition), with experimental designs differing with respect to one important aspect: Target Prevalence. Some designs include "target absent" (TA) among "target present" (TP) trials. In visual search tasks, TA trials shift an observer's decisional criterion towards a stricter one, increasing misses. However, decisional biases will differ between individuals and across an individual's decisions as well. In this way, excluding TA trials ensures comparable levels of expectation and thus a more controlled decisional bias both within and between observers by not considering correct rejections and false alarms. However, TA trials may occur, e.g., in police line-ups, where it is important to consider observers' face recognition ability net of the potential biases introduced by TA and TP trials. And, while these have been investigated in numerous other stimulus domains, their effects have not yet been extended to face recognition. We therefore sought to fill this void by testing different versions of the previously established Models Memory Test, which measures old/new recognition of experimentally learned facial identities. Our study found significant expectation effects, driven by target prevalence that persist even given prevalence changes. This implies that face recognition - even measured with naturalistic changes - is influenced by prior perceptual decisions.