Shoot or pass? Humans can prepare to move for different purposes in parallel

Just as Rubin's vase can appear to be a vase or two faces, multiple perceptual states can be present on a single time axis. However, it is difficult to understand how this theoretical concept can be applied to physical movements that eventually converge to a single state. We focused on the change in motion from shooting to passing during a jump shot in basketball and examined how far the shooter can respond to the change when the purpose, which was initially uncertain, is suddenly clarified. The timing of the visual stimuli presentation, which signifies the change in purpose to a pass, was strictly controlled, and 10 basketball players performed jump shots with the possibility of the purpose being changed to a pass. The shots maintained a high success rate regardless of the time at which the visual stimuli were turned on; furthermore, the success rate of the pass did not reach 0% until just before the ball was released (at least approximately 50 ms ago). These experimental results show that shooters can prepare to shoot and pass in parallel rather than in series. In a further validation experiment on kinematics during a possible change in purpose, strategies were observed in which individuals paused the elbow joint angle in mid-air and delayed the timing of the ball release. This is an example of how humans prepare to make multiple movements with different purposes in parallel, which can be transferred to either pattern if the movement is analogous to common motions.