Visual analysis of changes of motion in reaction-time tasks

Subjects observed a random-dot pattern moving uniformly in the vertical direction (vector V-1). The motion vector abruptly changed to V-2, both in speed and direction simultaneously It was found that the time of simple reaction to such changes V-1 -> V-2 can be described by a function of a single variable, vertical bar w(V-1 - V-2C) + (1 - w)V-2N vertical bar 0 < w < 0.5, where V-2C and V-2N are the components of V-2 collinear with and normal to V-1. The choice-reaction time for changes in direction that are accompanied by changes in speed can be described by a function Solely of the absolute value of V-2N. Unlike the simple-reaction time, the choice-reaction time was independent of the initial speed of motion. The processes that may be engaged in simple and choice reactions to motion are discussed.