Eye-Head Coordination During Rapid Gaze Shifts in Soccer Scanning
The visual exploratory behavior involving rapid gaze shifts that supports cognitive processes is called scanning. Scanning in soccer is a foundational behavior that enables players to explore their environment, supporting rapid and accurate decision-making. However, since most previous studies have focused on head movements, the coordination structure of gaze shifts, including the ocular contribution, is insufficiently understood. This study aimed to determine the coordinated roles of the eye and head during scanning. Twenty male collegiate soccer players performed a passing task paired with video-based situational judgments while eye and head movements were recorded by a 200 Hz sampling rate using an eye tracker system with a built-in gyroscope. We detected eye and head velocities and amplitudes during rapid gaze shifts. As a result, peak eye velocity was significantly higher than peak head velocity (d = 4.09, p < .001). The cross-correlation (CC) between gaze and eye velocities (0.98) was significantly greater than that between gaze and head velocities (0.90). These results indicate that gaze shifts were driven primarily by eye movements rather than head movements. Furthermore, eye and head velocities were negatively correlated (r = -.60, p = .005), whereas their velocity-control profiles (mean velocity normalized by amplitude) were positively correlated (r = .90, p < .001), indicating individual strategy-dependent allocation of effort while preserving control capability of eye and head movements. Our findings provide a characterization of the eye-head coordination structure of gaze shifts in soccer scanning, suggesting the need for comprehensive assessments beyond head-motion metrics alone.