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Takao Sato, Takuro Kayahara; Visual capture of auditory motion. Journal of Vision 2002;2(7):666. doi: 10.1167/2.7.666.
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© ARVO (1962-2015); The Authors (2016-present)
We examined the capturing effect of visual motion on auditory motion created by manipulating interaural intensity difference (IID), interaural time difference (ITD), and both.
Method: Visual stimulus was a moving disk filled with random dots. The diameter of the disk was varied in 5 steps: 5, 10, 20, 40, and 80 deg. The random dots had a density of 12.5%. The disk was moved at 20 deg/sec. The auditory stimulus was random noise (100 – 4500Hz) of 65dB. In Exp. 1, IID was varied at a steady rate over time. The changing rate was varied in 5 steps: plus/minus 0, 1, 2 dB/sec. In Exp. 2, ITD was varied again at a steady rate taken from 5 values: plus/minus 0, 178, 345 micro s. In Exp. 3, auditory motion was generated by using both IID and ITD. The change rate for IID motion was varied in 5 steps: plus/minus 0, 0.5, 1 dB/s, and that for ITD motion was varied in 5 steps: plus/minus 0, 90, 178 micro s. The two parameters were combined in the order in the list. The visual and auditory stimuli were presented together for 1 sec and subjects determined, while fixating to a marker, which direction the auditory stimulus perceived to move.
Results: All IID, ITD, and IID+ITD auditory motions were captured by visual motion. Stationary auditory stimuli were perceived to move in the same direction as visual stimuli, and direction decision was biased for moving auditory stimuli. Effects of size of visual target were also found, the capture was strongest with 20 deg and attenuated for both smaller and larger targets. The effect was not observed for the largest target (80 deg).
Conclusion: These results indicate that visual capture from visual to auditory motion is observed as long as the visual target was reasonably small. This probably comes from that smaller stimuli were interpreted as a moving target to which auditory motion can be attributed, but larger targets were interpreted as an environment itself.
Suported by HFSP grant to TS.
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