4 QUESTIONS OF TIME TO CONTACT - A CRITICAL-EXAMINATION OF RESEARCH ON INTERCEPTIVE TIMING

Four questions concerning the use and perception of time to contact, t (c), are identified. (i) Is t(c) information used in the timing of int erceptive actions? (ii) If so, what are used? (iii) What are the perce ptual sources of t(c) information and which of them do people use? (iv ) How is the information extracted by the perceptual systems? Research relevant to these questions is reviewed and analysed. In connection w ith question (i), theoretical work on the special case of catching a m oving object is analysed. It is concluded that treatments of catching which involve the use of t(c) information provide the best account of timing. In connection with question (ii), two types of control strateg y suggested in the literature are identified: an intermittent strategy and a continuous strategy. Evidence for a continuous strategy is reco nsidered and shown to be at least as well if not better accounted for by an intermittent strategy. Other empirical evidence for intermittent control is also discussed. In connection with question (iii) a simple unifying method is outlined with which all t(c) information so far pr esented in the literature can be derived, and examples are given. The viability of various types of information as sources of t(c) is examin ed by considering the errors which would result from their use. Finall y, in connection with question (iv) the role of 'looming detectors' in the extraction of t(c) information is considered. These are frequentl y proposed as mechanisms for extracting the t(c) information provided by Lee's optic variable, tau. The analysis provided indicates that, de spite the existence of a well-known and popular theory, due mainly to Lee, about how interceptive actions are timed, very little is actually known about perceptual timing. It is not yet certain whether t(c) inf ormation is used in interceptive timing tasks, what kinds of control s trategies are involved, what sources of information people use to time their actions, or what perceptual processing is involved in the extra ction of t(c) information.