Synchronising to a frequency while estimating time of vibro-tactile stimuli.

It is well known that subjective time perception can be modified by the emotional experience related to a specific event, by pharmaceutical compounds or by sensory stimuli. As for the latter, visual and auditory stimuli have been widely studied compared to tactile ones. Two experiments were conducted using different vibratory frequencies to stimulate participants who were asked to reproduce stimulus duration. Experiment 1 compared differences in reproduced times for 8-s stimuli ranging between 0.5 and 6 Hz in 100 participants who performed a time reproduction task with the stimulus present or absent during the reproduction. The task was done under prospective and retrospective paradigms. Experiment 2 assessed differences in reproduced times by 80 participants under vibrotactile stimulation of two frequencies simultaneously delivered to each hand, frequencies with specific proportions of 0.5 and 0.75 times the standard frequency for two groups of standard frequency (2 or 12 Hz). Reproduced times in Experiment 1 did not show significant differences among frequencies. Significant differences were found for the absence/presence condition, solely, in prospective tasks, where estimations were longer in the absence of the vibrotactile stimulus. Significant differences were found in Experiment 2 for reproduced time by participants between groups of standard frequency. Data analysis suggests the need to improve the understanding of the subjective time perception processes for higher frequencies considering the intensity modulation based on the amplitude and frequency relation. Results open the possibility of designing new protocols in the study of time perception and other cognitive functions.