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Shigekazu Takei, Waka Fujisaki, Shin'ya Nishida; Perceptual latency of sound-induced visual bounce. Journal of Vision 2008;8(6):361. doi: https://doi.org/10.1167/8.6.361.
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© ARVO (1962-2015); The Authors (2016-present)
Perceptual processing takes time, but the exact time course is unknown. The mystery is deepened by the fact that the perception of one event (target) is affected by another event (modulator) that occurs either before or after the event (prediction and postdiction). One might account for this flexibility by assuming that the processing of the target event waits for a constant period after the target appearance to register all the other potentially relevant inputs given before and after the target. A prediction of this conservative hypothesis is that the perceptual latency of the target event should be invariant against changes in the timing of modulator presentation. We tested this prediction by measuring the reaction time (RT) to judge an ambiguous motion event either as “bounce” or “stream” while changing the presentation timing of a modulatory sound. Subjects observed two black balls (0.4 deg in diameter) moving at 11.3 deg/s in opposite directions along the same path. A pip tone was presented through headphones at one of five SOAs (−140, −70, 0, +70 and +140 ms) from the balls' collision. Subjects had to report which event they saw by pressing one of two buttons as quickly and accurately as possible. The results show that, in comparison with the no-sound control, the sound increased the bounce response for SOAs between −140 and +70 ms. When subjects reported “stream”, no change in RT was observed between SOA conditions (∼400 ms, average of 6 subjects). However, when subjects reported “bounce", RT monotonically increased with SOA (∼300 ms for −140 ms SOA; ∼400 ms for +70 ms SOA). The result obviously contradicts the constant delay hypothesis. We consider that the processing of an event starts without delay and is flexibly updated by new relevant information.
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