Abstract
Previous work has investigated the visual control of interceptive movement. However, not much research has addressed the non-interceptability of targets. What makes a target impossible to intercept is a largely unexamined question that we addressed in this study. To identify the boundary between interceptable and non-interceptable balls, we adopted a manual lateral interception paradigm. Participants were instructed to intercept balls that moved down a screen using a hand-held slider, which mapped proportionately onto an on-screen paddle. Ball departure positions, ball arrival positions and speeds were varied. The experimental paradigm comprised 20% of catch trials in the form of balls that were designed to be non-interceptable. Participants were administered randomized blocks of trials wherein their interception performance was observed. A successful interception implies that the end effector (here the on-screen paddle) covers the distance to the interception location in the time that the ball also needs to arrive there. Analyses indicated that both the distance to be covered, and the time available for this determined interceptability. Interestingly, for some of the participants an effect of how the ball approached the interception axis (i.e., an angle-of-approach effect) could also be seen. Previously, this angle-of-approach effect has been established in studies of the prospective control of interception and has been instrumental for identifying the information in such tasks. However, the same has not yet been observed in the process of distinguishing interceptable from non-interceptable balls. This shared effect thus links prospective control of action together with decision-making, in the form of the action boundary for the affordance of interceptability. We conclude that what makes balls interceptable or not may well be understood in terms of the same optical variables that are at play in the visual control of interception.