Segmenting information into smaller parts helps to process it, and this is also true for temporal information. The aim of the present article is to compare the benefits of using explicit counting in a temporal discrimination task under various marker-type conditions and to show the limits of this strategy. In Experiment 1, conditions with and without counting were compared for two implicit standard durations, .8 and 1.6 s, in connection with three markertype conditions, which were intervals marked by: 1) two brief auditory signals (Auditory-Auditory); 2) two brief visual signals (Visual-Visual); and 3) one auditory signal followed by a visual signal (Auditory-Visual). At .8 s, markertype differences are significant (best in audition, worse with a bimodal sequence), and remain present with an explicit counting strategy. At 1.6 s, explicit counting provides clear improvements of performance in all marker-type conditions and annihilates marker-related differences. Experiment 1 also suggests that standard deviation remains constant from .8 to 1.6 s in the counting condition, while Experiment 2 shows that when standard intervals are extended up to 4 s, explicit counting does not totally prevent variance from increasing as base duration becomes progressively longer. The benefits derived from using explicit counting in duration discrimination are argued to depend (1) on a reduction of variance in the memory process involved in the timing mechanism, and (2) on a change in the decisional process.

We investigated how does the structure of empty time intervals influence temporal processing. In experiment 1, the intervals to be discriminated were the silent durations marked by two sensory signals, both lasting 10 or 500 ms; these signals were two identical flashes (intramodal: VV), or one visual flash (V) followed by an auditory tone (A) (intermodal: VA). For the range of duration under investigation (standards = 0.2, 0.6, 1, or 1.4 s), the results indicated that both the marker length and sensory mode influenced discrimination, but no interaction between these variables or between one of these variables and standard duration was significant. In experiment 2, we compared, for each of four marker-type conditions (VV, AA, VA, AV; and standard = 1 s), intervals marked by two 10 ms signals with intervals marked by unequal signal length (markers 1 and 2 lasting 10 and 500 ms, or 500 and 10 ms). As in experiment 1, the results revealed significant marker-mode and marker-length effects, but no significant interaction between these variables. Experiment 3 showed that, for the same conditions as in experiment 2, perceived duration is not influenced by marker length and that the variability of interval reproductions does not depend on the perceived duration of intervals. The results are discussed in the light of a single-clock hypothesis: marker-length and marker-mode effects are presented as being non-temporal sources of variability associated mainly with sensory and memory processes.

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