Studying the Processing of Multimodal Brief Temporal Intervals with an Equisection (Bisection) Task

Several studies have investigated the influence of auditory and visual sensory modalities on the variability and perceived duration of brief time intervals. However, few studies have investigated this influence when the two intervals to be discriminated share the same stimulus, and none of these have included the tactile modality. The aim of the present study was to investigate, in multimodal conditions, the capability to discriminate two adjacent intervals, using an equisection and adjustment method. Participants had to adjust the second of three brief successive signals marking two empty intervals until they were subjectively perceived as equal. The experiment included nine modality conditions and intervals between Markers 1 and 3 lasted 0.5, 1, 1.5, or 2 s (four standard conditions). The results show that the adjustment is better (lower variability) with three auditory (A) than with three visual (V) or tactile (T) markers, and these three conditions are better than when Marker 2 differs from Markers 1 and 3 (all intermodal conditions). Differences also emerged in the perceived duration of intermodal conditions. In TVT and VTV conditions, intervals marked by a tactile-visual (TV) sequence are perceived as longer than VT intervals, and in AVA and VAV conditions AV intervals are perceived as longer than VA intervals. Finally, AT intervals are perceived as longer than TA intervals, but only in the short standard conditions. In addition to replicating the classical variability increase when short intermodal intervals are used, the study shows the influence on perceived duration of the speed of processing of a visual signal.