PhD Thesis Defense
Title: "Human Duration Perception Mechanisms in the Subsecond Range"
In a world full of fleeting events, how do humans perceive time intervals as short as half a second? Unlike primary senses, there are no time receptors. Is sub-second time perception reconstructed from memory traces in the primary senses, or based on the output of a modality-independent internal clock? We studied two subjective time expansion (chronostasis) illusions in order to understand how time perception works. One illusion, oddball chronostasis, is the illusion that an unusual item appears to last longer. The other illusion, debut chronostasis, is the illusion that the first item among other identical ones seems to have longer duration. The findings showed that 1) oddball chronostasis is a composite illusion that arises from one perceptual and two cognitive factors, where top-down attention is a necessary cause, 2) debut chronostasis is stronger in within-modal (visual-visual, auditory-auditory) than in cross-modal modal (visual-auditory, visual-auditory) duration comparisons, suggesting the existence of an intra-modal time perception stage, and 3) debut chronostasis likely stems from uncertainty in the internal duration template, which is a supra-modal effect. Therefore, our results indicate that time perception in the subsecond range involves multiple cognitive factors. The evidence also suggests that time perception depends on both intra- and supra-modal mechanisms.