Approximate information sources and perceptual variables in interceptive timing.

D. N. Lee suggested that people time actions that involve the interception of a moving target using the information provided by the optic variable tau (τ). Using τ to time interceptions involves approximations that lead to errors in timing not reflected in human performance. Thus, it is to be expected that other perceptual information is used instead of or in addition to τ. Two additional variables are theoretically important: the instantaneous angle between the target and interception point and the target's rate of change of direction. Data suggest that these 2 variables are used in addition to τ. The data also demonstrate that when only the moving target is visible subjects do not rely on τ information alone to time interceptions