When to start explicit counting in a time-intervals discrimination task: A critical point in the timing process of humans

Four interval discrimination experiments were conducted to determine the interval length at which explicit counting becomes a useful strategy. Experiment 1 showed that for intervals lasting about 1 s, there was no advantage to counting regardless of the counting strategy adopted. Experiment 2 showed that for 2.5-s intervals, performance was much better with an explicit-counting strategy. To study the functional relationship between variability and duration in the counting versus no-counting conditions, variability was estimated for base durations lasting 0.7-1.9 s in Experiment 3. This experiment showed that the generalized form of Weber's law applied well to data in the no-counting condition. Experiment 4 showed that variability remained the same for durations lasting 1.3-1.9 s when an explicit-counting strategy was adopted. Taken together, the experiments showed that it becomes useful to count explicitly when intervals are longer than 1.18 s.