Control strategies when intercepting slowly moving targets

In 3 experiments, the authors investigated and described how individuals co ntrol manual interceptive movements to slowly moving targets. Participants (N = 8 in each experiment) used a computer mouse and a graphics tablet asse mbly to manually intercept targets moving across a computer screen toward a marked target zone. They moved the cursor so that it would arrive in the t arget zone simultaneously with the target. In Experiment 1, there was a ran ge of target velocities, including some very slow targets. In Experiment 2, there were 2 movement distance conditions. Participants moved the cursor e ither the same distance as the target or twice as far. For both experiments , hand speed was found to be related to target speed, even for the very slo wly moving targets and when the target-to-cursor distance ratios were alter ed, suggesting that participants may have used a strategy similar to tracki ng. To test that notion, in Experiment 3, the authors added a tracking task in which the participants tracked the target cursor into the target zone. Longer time was spent planning the interception movements; however, there w as a longer lime in deceleration for the tracking movements, suggesting tha t more visually guided trajectory updates were made in that condition. Thus , although participants scaled their interception movements to the cursor s peed, they were using a different strategy than they used in tracking. It i s proposed that during target interception, anticipatory mechanisms are use d rather than the visual feedback mechanism used when tracking and when poi nting to stationary targets.