Revealing the speed of implied motion signals associated with viewing other people's gaze.

Recent evidence has shown that exposure to static images depicting an agent actively gazing at an object leads to a motion adaptation effect in the direction of the gaze, suggesting that the attention of others is encoded as an implied agent-to-object motion. We examined whether this motion signal is associated with a specific speed by presenting the same static image used in previous studies, followed by test probes with differing speeds of dot motion. A peak significant motion adaptation effect was found for dot motion with a speed of 1.4° s-1. The effect disappeared when the agent was blindfolded. Moreover, adaptation to real motion at 1.4° s-1 was strongest when the test probe speed closely matched the adapting stimulus, suggesting similar underlying mechanisms. These findings strongly suggest that people encode others' gaze as an implied motion linking agents to attended objects, and that this internally generated motion signal travels at a specific 'speed'.