MULTIPLE INFORMATION-SOURCES IN INTERCEPTIVE TIMING

This study was designed to explore the limitations of tau (tau) as an explanatory construct for the timing of interceptive action. This was achieved by examining the effects of en environmental structure and bi nocular vision on the timing of the grasp in a simple one-handed catch . In two experiments, subjects were required to catch luminous balls o f different diameters (4, 6, 8 and 10 cm) in a completely darkened roo m. In the first experiment the influence of the presence vs, absence o f an environmental background structure (both under monocular viewing) was tested, and in the second experiment the influence of monocular v s. binocular vision was examined. It was found that irrespective of th e presence of environmental structure, an effect of ball size occurred in the monocular viewing conditions. That is, in monocular viewing co nditions the grasp was initiated and completed earlier for the larger balls as compared to the smaller ones, while in the binocular viewing condition subjects behaved in accordance with a constant time to conta ct strategy: no effects of ball size were found. It is concluded that under binocular viewing a binocular information source is used, while in the monocular viewing condition a lower order information source li ke image size or image velocity is probably involved. (C) 1997 Elsevie r Science B.V.