Optical Information to Guide the Head and Handle Movements While Playing Kendama

This study focuses on the perceptual skills used when playing kendama, a toy with a ball, string, and handle. It examines the visual information required for guiding the head and handle movements during the “swing-in” catching maneuver and determines whether information-based strategies such as canceling the rate of change of α (the optical depression angle from the horizon) or cot α (optical acceleration), using tau coupling, or a combination thereof, could be applied to this empirical task. The regressions of both α and cot α with time are found to be highly linear and increase when the skill level increases. For expert players, the k values for the tau coupling based on the center of the ball are clearly lower than those for the tau coupling based on the hole in the ball compared with skilled players. These results suggest that, with increasing skill level, kendama players tend to utilize α or cot α for regulating the observation point and use the sight of the hole as the tau coupling information for controlling the handle.