Multiple timing and the allocation of attention.

Two experiments were designed to examine the effects of multiple timing tasks on prospective time judgment performance. In experiment 1, subjects were required to monitor the durations of one, two, three, or four concurrent target stimuli which began and ended at different times, and then reproduce one of those durations subsequently chosen at random. Time judgment accuracy deteriorated as the number of target stimuli increased. In experiment 2, subjects used the production method to generate specified durations for one, two, three, or four partially overlapping stimuli. Timing was less accurate in conditions involving more target stimuli. In the multiple-target conditions, time judgments were less accurate for the later- rather than earlier-onset targets. The results support an attentional model of timing, and suggest that timing is an effortful process which draws from limited attentional resources.