Abstract
Dynamic or attended visual stimuli are known to lengthen their perceived duration. What if a sound is added to the visual onset? Two contrasting predictions can be made based on the integration hypothesis and the distraction hypothesis respectively. If the sound is integrated into the visual onset and forms an integrated event, it is predicted that adding a sound should increase the perceived duration of this event. However, if the sound works to direct one's attention away from the visual stimulus, its perceived duration should be decreased instead. We adopted an oddball paradigm similar to that in Tse, Intriligator, Rivest, and Cavanagh (2004) to test these two hypotheses. An oddball was inserted into a sequence of visual standards, and the perceived duration of the oddball was measured with the method of constant stimuli. The points of subjective equality were computed separately for the oddballs with or without a tone. Results show clearly a subjective time expansion for the oddballs with the tone, compared to when the tone is absent, thus supporting the integration hypothesis. We conclude that the added sound is integrated into the visual onset and they become an integrated event which has a lengthened perceived duration than a uni-modal stimulus.
[Supported by the National Science Council of Taiwan, NSC95-2752-H-002-007-PAE and 95-2413-H-002-020]