#Cross modal perception definition trial

This was confirmed by the experiments where a sudden visual flash (exogenous attention distraction) or an additional task (endogenous attention distraction) at the moment of the visual coincidence also enhanced the bouncing percept. If the motion mechanism responsible for the dominance of the streaming percept requires attention and a salient sound attracts attention automatically, the bounce-inducing effect would results. These results suggest that there is an aspect of auditory-grouping (saliency-assigning) processes which is context-sensitive and can be utilized by the visual system for ambiguity solving.īased on the finding that the saliency of sound is crucial for the bounce-inducing effect, I hypothesized that an allocation process of crossmodal attention may be involved in this audiovisual effect. The attenuation occurred only when the simultaneous sound and auditory flankers has similar acoustic characteristics and the simultaneous sound was not salient. Subsequent experiments showed that the bounce-inducing effect depends on auditory context.įor example, the effect was attenuated when the simultaneous sound was embedded in other identical sounds (auditory flankers) with an sound-onset-asynchrony of about 300 ms. Likewise, the spatial interaction range is wide: With a separation up to 30-deg of visual angle between the sound and the visual display, the bounce-inducing effect was virtually unchanged. We found that a sound can bias the perception even when it was presented from 250-ms before to 150-ms after the visual coincidence, suggesting that the temporal interaction range is rather long. By using this ambiguous motion display and the bounce-inducing effect, we determined an interaction range for audiovisual event classification. A brief sound at the moment the targets coincide biases perception toward bouncing (Sekuler et al., 1997). Two identical visual targets moving across each other can be perceived either to bounce off or to stream through each other (Metzger, 1934). The observed illusion (as well as its non-requirement of spatial concordance between the auditory and visual stimuli) can be explained based on prior behavioral findings relating the audio-visual sensory interactions.Īudiovisual attention and visual motion perception The illusion does not appear to be a result of eye movements, as the effect is stronger with shorter flash durations, persists with very large disk size, and degrades with decrease in disk contrast. The observed illusory flash effect does not seem to be due to general attentional enhancement caused by auditory stimulation, as there is no illusory flash elicited by a single beep. and spatial concordance between the auditory and visual stimuli is not necessary.Ĭonclusion: AAS can alter the visual percept qualitatively and significantly. The results are robust to many parameters namely the duration of the visual flash, the flashing visual pattern, the size of the visual pattern, etc. A single flash is reported in trials with single beep.

In other words, the sound beeps induce the perception of 'visual beeps.' Moreover, the number of flashes perceived in each trial is correlated significantly with the number of beeps in the same trial. Subjects perceive the single flash as more than one flash in the condition where the flash is accompanied with auditory beeps, and not otherwise. Results: Although the visual stimulus is identical across all trials (a single flash), the percept of the visual stimulus varies drastically across trials. The subjects’ task is to judge the number of flashes displayed on the screen in each trial. In one condition, the flash is accompanied by a brief sound stimulus which consists of 1 to 3 beeps (with the number and pitch of the beeps randomized across trials), and in another condition, the visual stimulus is not accompanied by any auditory signal. Methods: In each trial, a disk is flashed for 13.3ms in the center of a computer screen (where the subjects fixate). We investigated whether the visual percept itself can be modified by such auditory stimulation. AAS is an auditory stimulus that is presented in close temporal proximity of the visual stimulus and which is not to be responded to. Purpose: Various studies have shown the modulation of perceived intensity, detectability, spatial and temporal localization of visual stimuli by an accessory auditory stimulus (AAS). Illusory Flashing Visual Percept Induced by Sound.

#Cross modal perception definition trial