A systematic survey of face stimuli used in psychological research 2000-2020

For decades, psychology has relied on highly standardized images to understand how people respond to faces. Many of these stimuli are rigorously generated and supported by excellent normative data; as such, they have played an important role in the development of face science. However, there is now clear evidence that testing with ambient images (i.e., naturalistic images "in the wild") and including expressions that are spontaneous can lead to new and important insights. To precisely quantify the extent to which our current knowledge base has relied on standardized and posed stimuli, we systematically surveyed the face stimuli used in 12 key journals in this field across 2000-2020 (N = 3374 articles). Although a small number of posed expression databases continue to dominate the literature, the use of spontaneous expressions seems to be increasing. However, there has been no increase in the use of ambient or dynamic stimuli over time. The vast majority of articles have used highly standardized and nonmoving pictures of faces. An emerging trend is that virtual faces are being used as stand-ins for human faces in research. Overall, the results of the present survey highlight that there has been a significant imbalance in favor of standardized face stimuli. We argue that psychology would benefit from a more balanced approach because ambient and spontaneous stimuli have much to offer. We advocate a cognitive ethological approach that involves studying face processing in natural settings as well as the lab, incorporating more stimuli from "the wild".