What is it about?
Sensory signals from our eyes and ears arrive at their different destinations in the brain at different times. How then can we determine when events actually occur in the world? This study helps to understand why, even though we never know for sure, our brain's best guess is on average correct. It is shown that sight and sound are consistently out of synch in different individuals by different amounts, and for different tasks. Curiously, the more an individual’s vision lags their audition in the performance of one task, the more their audition is likely to lag vision in other tasks. Such compensatory delays result in perceptual timing that is approximately correct on average.
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Why is it important?
It is found that speech comprehension can sometimes actually improve by as much as 10% when sound is delayed relative to vision. This has some potential applied benefits. For example, by tailoring sound delays on an individual basis via a hearing aid or cochlear implant, or a setting on a computer media player, there could be benefits for speech comprehension and enjoyment of multimedia.
Perspectives
Aside from some exciting possible applied advances, we think this study also provides some new theoretical insights into the deep problem of how we determine when events actually occur in the world, given that our senses are intrinsically out of sync with each other. To understand the theory, consider the following analogy. Imagine standing in an antique shop full of clocks, and you want to know what the time is. Your best guess comes from the average across clocks. However, if one clock is particularly slow, others will seem fast relative to it. In our new theory of 'temporal renormalisation’, the ‘clocks’ are analogous to different mechanisms in the brain which each receive sight and sound out of sync: but if one such mechanism is subject to an auditory delay, this will bias the average, relative to which other mechanisms may seem to have a visual delay. Unlike other traditional theories, only this theory can explain the curious finding that different tasks show opposite delays. In so doing, the theory help to explain how we know when events in the world are actually happening, despite our brains having many conflicting estimates of their timing.
Elliot Freeman
City University
Read the Original
This page is a summary of: Correlation of individual differences in audiovisual asynchrony across stimuli and tasks: New constraints on temporal renormalization theory., Journal of Experimental Psychology Human Perception & Performance, August 2018, American Psychological Association (APA),
DOI: 10.1037/xhp0000535.
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