Quantifying the cognitive trajectories of extrapolated movements.

Subjects' extrapolations of a piecewise constant-velocity trajectory and a constant-acceleration trajectory were mapped out over a sequence of trials that required only a button-press response. Without any performance feedback, subjects' extrapolations of both trajectories approximated an acceleration segment followed by a constant-velocity segment. With performance feedback, subjects' extrapolations of the constant-acceleration trajectory approached optimal performance. Subsequent withdrawal of the feedback shifted the entire extrapolated trajectory. These feedback-related changes in the extrapolated trajectory can be interpreted as changes in two parameters of a cognitive representation of the movement pattern.