Perceptual and cognitive processes in time-to-contact estimation: analysis of prediction-motion and relative judgment tasks.

Three classes of task appear to involve time-to-contact (TTC) information: coincidence anticipation (CA) tasks, relative judgement (RJ) tasks, and interceptive actions (IAs). An important type of CA task used to study the perception of TTC is the prediction-motion (PM) task. The question of whether it is possible to study the perceptual processes involved in the timing of IAs using PM and RJ tasks is considered. A revised version of the tau hypothesis is proposed as an account of the perceptual information processing involved in the control of fast IAs. This draws on the distinction between "motor" and "cognitive" visual systems. It is argued that task variables affect whether "cognitive" information processing is involved in performance and can determine whether TTC information is used at all. Evidence is reviewed that suggests that PM and RJ tasks involve cognitive processing. It is argued that target viewing time, TTC at response initiation, amount of practice, and whether there is a period between target disappearance and response are task variables that determine whether cognitive processing will influence responding.