Abstract
Perception of a temporal pattern in a sub-second time scale is fundamental to conversation, music perception, and other kinds of sound communication. However, its mechanism is not fully understood. A simple example is hearing three successive sounds with short time intervals. The following misperception of the latter interval is known: underestimation of the latter interval when the former is a little shorter or much longer than the latter, and overestimation of the latter when the former is a little longer or much shorter than the latter. Although this misperception of auditory time intervals for simple stimuli might be a cue to understanding the mechanism of time-interval perception, there exists no model that comprehensively explains it. Considering a previous experiment demonstrating that illusory perception does not occur for stimulus sounds with different frequencies, it might be plausible to think that the underlying mechanism of time-interval perception involves a causal inference on sound sources: herein, different frequencies provide cues for different causes. We construct a Bayesian observer model of this time-interval perception. We introduce a probabilistic variable representing the causality of sounds in the model. As prior knowledge, the observer assumes that a single sound source produces periodic and short time intervals, which is consistent with several previous works. We conducted numerical simulations and confirmed that our model can reproduce the misperception of auditory time intervals. A similar phenomenon has also been reported in visual and tactile modalities, though the time ranges for these are wider. This suggests the existence of a common mechanism for temporal pattern perception over modalities. This is because these different properties can be interpreted as a difference in time resolutions, given that the time resolutions for vision and touch are lower than those for audition.
Highlights
Temporal pattern processing is necessary for all sensory modalities and these patterns contain much essential information for our brain to learn what happens in the external world
With regard to hearing three rapid sounds on a hundred-millisecond scale, it is known that our brain sometimes misestimates the second interval depending on the relative length of the two intervals
Though the degrees of misestimation are not so large as those for the case of the timeshrinking illusion, the following phenomena on the perception of T 2 have been observed (Miyauchi and Nakajima, 2005; Figure 1A): overestimation of T 2 when T 2 is a little shorter than T 1; underestimation of T 2 when T 2 is much shorter than T 1; and overestimation of T 2 when T 2 is much longer than T 1
Summary
Temporal pattern processing is necessary for all sensory modalities and these patterns contain much essential information for our brain to learn what happens in the external world. Hearing three rapid successive sounds is a good situation for investigating the time-perception system. Speaking, the second interval, T 2, is perceived as shorter than the actual length in the case where T 2 is equal to or a little longer than the first interval, T 1 This perceptual underestimation phenomenon was named “timeshrinking” (Nakajima et al, 1991). One reasonable way for the brain to cope with the uncertainty is exploiting prior knowledge, or the experience and statistics pertaining to the situation This strategy can be formulated by using Bayesian inference. Bayesian modeling is a powerful method for describing the human perception mechanism and has been applied to visual temporal perception (Miyazaki et al, 2005; Jazayeri and Shadlen, 2010), and more widely to human perception (Vilares and Körding, 2011, for a recent review)
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