Learning to throw to maximum distances: do changes in release angle and speed reflect affordances for throwing?

Area of Science:

• Human motor control
• Perceptual-motor skill acquisition
• Biomechanics of throwing

Background:

• Skilled throwers can select object weight for maximum distance throws, suggesting a perceptual mechanism (Bingham et al., 1989).
• Unskilled throwers initially lack this perception but acquire it with throwing practice (Zhu & Bingham, submitted).
• The affordance relates object size and weight, but its direct impact on throwing mechanics during learning was unclear.

Purpose of the Study:

• To investigate how object size and weight influence throwing performance as skill is acquired.
• To test the hypothesis that the perceived affordance for maximum distance throwing is directly reflected in throwing mechanics.
• To explore alternative explanations for the relationship between perception and action in throwing.

Main Methods:

• Three groups of unskilled adults practiced throwing for one month.
• Each group used objects with either constant size, constant weight, or constant density.
• Kinematic variables (release angle, speed) and throwing distance were analyzed.

Main Results:

• Throwing distance and consistency of release angle and speed improved with practice.
• Mean release speeds changed, decreasing as object weight increased, following a power law (Cross, 2004).
• Object size did not significantly affect throwing performance.
• The perceived affordance was not directly evident in the throwing mechanics.

Conclusions:

• The direct perception-action hypothesis regarding throwing affordances was not supported.
• Object weight influences throwing speed, but this relationship does not directly mirror the perceived affordance for maximum distance.
• An alternative account for learning to perceive and utilize throwing affordances is proposed.