Presence of a human catcher affects performance in a ball-throwing task.

Target characteristics can influence motor performance in goal-directed tasks by affecting cognitive and affective processes. This study investigated whether motor performance in a ball-throwing task differed when the target was held by a person, compared with when the target was a physical mark. Eighteen healthy adults without baseball experience participated. Each participant threw 15 fastballs across three blocks, each with a different target condition. In the Mark condition, the target was a visible mark on the net. In the Humanoid condition, the same mark was placed on a humanoid board. In the Catcher condition, the mark was held by a person. Mean ball speed, absolute error of arrival positions, pupil diameter, and subjective ease of throwing were compared across conditions. Mean ball speed and absolute error were significantly lower in the Catcher condition than in the other two conditions. Conversely, pupil diameter and subjective ease were significantly higher in the Catcher condition. These results indicate that when the target is held by a person, participants prioritized accuracy over speed. Increased pupil diameter in the pre-movement state suggests heightened arousal in the Catcher condition, which was associated with improved accuracy. Subjective ease also increased in this condition. These findings suggest that an implicit social or safety-related goal of allowing the person to catch the ball, such as safety and harm-avoidance considerations for the catcher, led participants to focus more on precise throws, contributing to the understanding of how cognitive and affective processes influence motor control.