The quantitative use of velocity information in fast interception.

We ask whether a target's velocity is considered when planning a fast interceptive action. Human volunteers hit targets that could move at different velocities from across a tilted screen (the hand starting 40 cm away from the screen). We examined how the direction in which the hand initially moved depended on the target's velocity, using various analyses. For slow targets, the initial movement direction was appropriate for the target's velocity. This is evidence that velocity information was used quantitatively in directing the hand. A model analysis showed though that velocity information is probably not used to predict the future target position. For targets moving at a velocity above average, or above 12 cm/s, the initial movement direction did not depend on the target's velocity. Similar behaviour is also known from pursuit eye movements. Copyright 2004 Springer-Verlag