The effects of crowd gaze on visual search

Crowd gaze is a social visual cue that signals the direction of a crowd’s attention. This statistical ensemble cue has high social relevance, providing important information about the environment. Studies showed that our visual system can extract the global gaze direction from a crowd of faces. However, whether the human visual system utilizes the crowd gaze direction to guide behavior is not yet known. Here, we investigated this question in the context of visual search and tested the hypothesis that crowd gaze can enhance search performance. Participants located a target face among distractor faces. In Experiment 1 (n = 36), we manipulated the gaze coherence (the proportion of distractor faces looking at the target face; 0%, 50%, 100%) and the number of distractors (2, 4, 8). In Experiment 2 (n = 39), we repeated the task with inverted faces. In Experiment 3 (n = 38), we manipulated the validity of the gaze cue (valid: crowd gaze towards the true target; invalid: towards a pseudo-target; neutral: random gaze), with 8 distractors. Reaction time (RT) was measured to characterize the visual search performance. Overall, RT increased with the number of distractors, but the rate of increase was smaller for conditions with larger gaze coherence (Experiment 1). This suggests an improvement in search efficiency as a function of gaze coherence. This benefit from the crowd gaze disappeared when the faces were inverted (Experiment 2), indicating that low-level visual cues cannot explain the observed benefit in Experiment 1. Furthermore, invalid crowd gazes had a detrimental effect, leading to longer RT than when the cue was valid (Experiment 3). Together, the findings demonstrate the effect of crowd gaze in facilitating visual search. The results provide insights into how human observers can rely on a high social cue to guide their visual behavior.