The time it takes to make judgments of velocity.

Abstract

Reaction times were measured in an absolute judgment experiment involving either the location of a point on a screen, or the direction of a moving point, or its velocity. Stimuli were chosen to be almost perfectly detectable and discriminable when presented pairwise to avoid confusions at the sensory coding level. Typical results associated with absolute judgment tasks were observed, as to the amount of information transmission and anchoring effects. More in particular, latencies appear to be a direct function of the number N of alternatives. For N constant, responses are much slower for velocity than for both location and direction. This difference itself is a direct function of N, and, presumably, drops to zero for N = 1, i.e., when stimulus uncertainty vanishes. These observations support the idea that the difference should not be attributed to some velocity-specific integration of space and time but to some performance decision strategies in evaluation of magnitude.