In this set of two experiments we tried to study how two different systems, a rhythmic and a memory-based one, can work together to generate explicit time perceptions. Using a time estimation task, participants were asked to report the duration of a visual stimulus appearing for a random interval ranging from 1 to 8 seconds. In one condition participants had to count the seconds before responding. In a different block participants were told not to count and simply
guess the time. Both strategies produced greatly different performance functions: 1) the counting strategy presented similarly fast reaction times as a function of interval and better discrimination in general; 2) the non-counting condition produced an inverted U-shape distribution in which extremes were responded to faster than intermediate values. This function was also linked to a
pattern of poor discrimination in the extreme intervals, with clear overshooting in the shorter and undershooting in the longer ones. More importantly, manipulation of verbal distraction and alterations to a rhythm produced an impact in the counting condition only, but not in the noncounting one. The results are interpreted under a combination of clock-based and memory-based
systems that coexist to produce explicit time estimations.