Shifted visual feedback of the hand affects reachability judgments in interception

Estimating whether an object is reachable is important if one intends to interact with the object. If an object is moving, it will be reachable only within a certain time-window. In such situations, motion of the object relative to the body has to be taken into account to judge the moment at which the target becomes reachable. We know that judgments of reachability are influenced by displaced visual feedback about the position of the hand when objects are static. Here we examine whether displaced feedback of the hand also influences reachability judgments when reachability is temporally constrained because the object is moving. The task for the subjects was to intercept a virtual cube with their unseen index finger as soon as the cube was considered to be reachable. Subjects received visual feedback about the position of their index finger, but this feedback was shifted in depth by 5 cm, either away from or closer to their body. The region that was judged to be reachable was larger when feedback of the hand was shifted away from the body than when the feedback was shifted closer to the body. This effect was correlated with the spatial error committed at the interception point. We conclude that all judgments about the surrounding space are adjusted in relation to the shifted visual feedback of the hand.