The psychophysics of dynamic gaze-following saccades during search.

The ability to quickly and precisely follow another person's gaze reflects critical evolutionary mechanisms underlying social interactions, such as attention modulation and the prediction of others' future actions. Recent studies show that observers use another person's gaze direction and peripheral scene information to make anticipatory saccades toward the gaze goal. However, it remains unclear how these eye movements are influenced by complex features of natural scenes, such as a foveal gazer, multiple peripheral gaze goals, and the relative distance between gazer and goal. We presented dynamic stimuli (videos) of real-world scenes with or without a gazer shifting their head to gaze at other individuals (gaze goals). Participants were instructed to search for a specific target individual in the videos while their eye movements were recorded. We measured the accuracy of the first saccade in locating the gaze goal. First, we found that the absence of a foveal gazer significantly increased saccade error, but only when the goal was at least approximately 9 degrees of visual angle from the initial fixation. First saccade amplitude and onset latency were higher in the gazer-present condition. Second, when there were multiple potential gaze goals in the periphery, the first saccade was directed to the individual closer to the initial fixation (gazer) location. Finally, the presence of multiple peripheral gaze goals shortened saccade latencies and increased the frequency of anticipatory saccades made before the gazer completed their head movement. These findings extend our understanding of gaze following in complex, naturalistic scenes and inform theories of attention and real-world decision-making.