Making time: Estimation of internally versus externally defined durations

Most research on the topic of duration estimation has examined the mechanisms underlying estimation of durations that are demarcated by experimental stimuli. It is not clear whether the estimation of durations that are instead defined by our own mental processes (e.g., response times) is underlain by the same mechanisms. Across five experiments, we tested whether the pattern of interference between concurrent temporal and nontemporal tasks was similar for the two types of intervals. Duration estimation of externally defined intervals slowed performance on a concurrent equation verification task, regardless of whether participants were required to report their estimate by clicking within an analogue scale or by reproducing the duration. Estimation of internally defined durations did not slow equation verification performance when an analogue scale response was required. The results suggest that estimation of internally defined durations may not depend on the effortful temporal processing that is required to estimate externally defined durations.