Developmental trajectories of head and eye cue integration in gaze perception.

Gaze perception is a foundational social skill. Here, we investigated how head and eye cue integration in gaze perception changes across development. Across five experiments involving 195 Japanese children (ages 4-16) and 126 adults (ages 18-58), we tested eye gaze perception using both Wollaston illusion images, where eye regions remain identical across head orientations, and Normal images with naturally varying eye regions. We found that the attractive influence of head orientation, whereby perceived gaze is biased toward the head direction, decreased from early childhood to adolescence. Notably, children aged 10-16 years did not show the attractive effect of head orientation characteristic of the Wollaston illusion. Adults consistently showed the illusion as expected. These findings highlight adolescence as a critical transitional period. A follow-up experiment with 7-9-year-old children showed that perceived gaze direction was more strongly biased toward head orientation in smaller images where iris and pupil positional details are less clearly visible, suggesting that the influence of head orientation is flexibly modulated by the clarity of eye region as well as age. The findings provide new insights into the dynamic development of social cue integration and perceptual decision-making across childhood, adolescence, and adulthood.