Temporal Reference, Attentional Modulation, and Crossmodal Assimilation

Robust Temporal Averaging of Time Intervals Between Action and Sensation

Perception of the time interval between one’s own action (a finger tapping) and the associated sensory feedback (a visual flash or an auditory beep) is critical for precise and flexible control of action and behavioral decision. Previous studies have examined temporal averaging for multiple time intervals and its role for perceptual organization and crossmodal integration. In the present study, we extended the temporal averaging from sensory stimuli to the coupling of action and its sensory feedback. We investigated whether and how temporal averaging could be achieved with respect to the multiple intervals in a sequence of action-sensory feedback events, and hence affect the subsequent timing behavior. In unimodal task, participants voluntarily tapped their index finger at a constant pace while receiving auditory feedback (beeps) with varied intervals as well as variances throughout the sequence. In crossmodal task, for a given sequence, each tap was accompanied randomly with either visual flash or auditory beep as sensory feedback. When the sequence was over, observers produced a subsequent tap with either auditory or visual stimulus, which enclose a probe interval. In both tasks, participants were required to make a two alternative forced choice (2AFC), to indicate whether the target interval is shorter or longer than the mean interval between taps and their associated sensory events in the preceding sequence. In both scenarios, participants’ judgments of the probe interval suggested that they had internalized the mean interval associated with specific bindings of action and sensation, showing a robust temporal averaging process for the interval between action and sensation.

Illusory perception of auditory filled duration is task- and context-dependent

In filled-duration illusion, a continuous (long) tone or an auditory sequence with multiple clicks is typically perceived as longer than the same physical duration (i.e., empty interval) enclosed by two auditory clicks. The auditory sequence is composed of multiple empty intervals. However, the individual empty interval in an auditory sequence, compared with the empty interval presented alone, could be biased in duration perception. In the current study, we implemented five experiments to reveal that the time perception of a single empty interval versus that of (mean) empty intervals in an auditory sequence depends on the task demands and contextual information. Specifically, we observed that the empty interval (140 ms) was perceived as longer than the same physical inter-stimulus interval in a sound sequence (Experiments 1 and 3). However, the empty interval (140 ms) was perceived as shorter than a continuous beep (i.e., filled duration of 140 ms) (Experiment 2). We observed a robust compression effect, in which the target empty interval (bounded by two oddball clicks) was perceived as shorter than the other physically equivalent intervals in a sound sequence (Experiment 4). In addition to the 'compression', perception of the target empty interval was assimilated by the other, task-irrelevant empty intervals in the sound sequence (Experiment 5). We explained the observed contextually modulated temporal illusions within a Bayesian inference framework.