Bringing about desirable collisions (making interceptions) and avoiding unwanted collisions are critically important sensorimotor skills, which appear to require us to estimate the time remaining before collision occurs (time-to-collision). Until recently the theoretical approach to understanding time-to-collision estimation has been dominated by the tau-hypothesis, which has its origins in J.J. Gibson’s ecological approach to perception. The hypothesis proposes that a quantity (tau), present in the visual stimulus, provides the necessary time-to-collision information. Empirical results and formal analyses have now accumulated to (...) demonstrate conclusively that the tau-hypothesis is false. This article describes an alternative approach that is based on recent data showing that the information used in judging time-to-collision is task- and situation-dependent, is of many different origins (of which tau is just one) and is influenced by the information-processing constraints of the nervous system. (shrink)

The λ model suggests that detailed kinematics arise from changes in control variables and need not be explicitly planned. However, we have shown that when moving a grasped object, grip force is precisely modulated in phase with acceleration-dependent inertial load. This suggests that the motor system can predict detailed kinematics. This prediction may be based on a forward model of the dynamics of the loaded limb.