Searching for a face in the crowd: Pitfalls and unexplored possibilities.

Finding a face in a crowd is a real-world analog to visual search, but extending the visual search method to such complex social stimuli is rife with potential pitfalls. We need look no further than the well-cited notion that angry faces "pop out" of crowds to find evidence that stimulus confounds can lead to incorrect inferences. Indeed, long before the recent replication crisis in social psychology, stimulus confounds led to repeated demonstrations of spurious effects that were misattributed to adaptive cognitive design. We will first discuss how researchers refuted these errors with systematic "face in the crowd" experiments. We will then contend that these more careful studies revealed something that may actually be adaptive, but at the level of the signal: Happy facial expressions seem designed to be detected efficiently. We will close by suggesting that participant-level manipulations can be leveraged to reveal strategic shifts in performance in the visual search for complex stimuli such as faces. Because stimulus-level effects are held constant across such manipulations, the technique affords strong inferences about the psychological underpinnings of searching for a face in the crowd.