Localization (Part 2)
Although I know it can’t be true given the time frame, I like to think the person who discovered motion parallax did it on a Texas panhandle highway. Since the only objects to look at most of the time are barbed wire fences and cows, the observation is easy to make: the cows that are close to the highway practically fly through the visual field with a “whoosh” sound, appearing to move the opposite direction of the vehicle. The cows far away from the highway seem to stay in the same place forever, or even travel along in the same direction as the vehicle, but at an extremely slow place. I imagine most of us Texas highway frequenters don’t give a lot of thought to the fact that this apparent motion actually serves as a depth cue to tell us how close the cows are to us relative to each other. Even fewer of us would probably think that the motion parallax depth cue also applies to sound localization, but that’s probably because the research is pretty new.
The article “Psychophysical evidence for auditory motion parallax,” which was published March 12, 2018, details a psychophysical experiment which tests motion parallax with sound. As always, you can access the article and read the details either through the Cited Articles section of this site or the citation at the end of this post. In summary, the experiment’s data suggest that the most effective condition for localization is when the subject moves voluntarily. This suggests that there is an area of the brain which not only effectively segregates sounds by their depth, but also reconciles self-motion with binaural processing. Put simply, this means that while your brain tells you how and where to move AND processes the sounds you are hearing and attempts to determine where they are coming from, it is also integrating the two to produce the clearest, most accurate perceptual scene.
So what is the significance of this finding?
Well for one thing, it can serve as a pro tip. If you are trying to discern the location or distance of a sound source and you just can’t figure it out, try moving around. This will potentially activate the pathway of your brain that makes motion and localization work together to be an overall more effective system.
This research has particularly important implications for people with unilateral hearing loss or cochlear implants, who struggle with pure localization because the sounds they perceive are either inaccurately perceived or slightly modified. Perhaps in the future technology could be modified or improved to fit this new possibility, or new techniques could be introduced in the process of aural rehabilitation to help people localize more creatively, but equally effectively.
A broader application raises the question of the importance of localization in general, but if you’re asking why localization matters, you probably have not needed to live without it. It affects everything you do without you even consciously thinking about it. Examples include classroom learning environments, crossing the street safely, interacting with people in noisy environments, and so many other things. It would make sense to assume people just couldn’t survive without localization. The real phenomenon here is that some people do. But more on that later.
Daria Genzel, Michael Schutte, W. Owen Brimijoin, Paul R. MacNeilage, Lutz Wiegrebe. Psychophysical evidence for auditory motion parallax. Proceedings of the National Academy of Sciences, 2018; 201712058 DOI: 10.1073/pnas.1712058115
The article “Psychophysical evidence for auditory motion parallax,” which was published March 12, 2018, details a psychophysical experiment which tests motion parallax with sound. As always, you can access the article and read the details either through the Cited Articles section of this site or the citation at the end of this post. In summary, the experiment’s data suggest that the most effective condition for localization is when the subject moves voluntarily. This suggests that there is an area of the brain which not only effectively segregates sounds by their depth, but also reconciles self-motion with binaural processing. Put simply, this means that while your brain tells you how and where to move AND processes the sounds you are hearing and attempts to determine where they are coming from, it is also integrating the two to produce the clearest, most accurate perceptual scene.
So what is the significance of this finding?
Well for one thing, it can serve as a pro tip. If you are trying to discern the location or distance of a sound source and you just can’t figure it out, try moving around. This will potentially activate the pathway of your brain that makes motion and localization work together to be an overall more effective system.
This research has particularly important implications for people with unilateral hearing loss or cochlear implants, who struggle with pure localization because the sounds they perceive are either inaccurately perceived or slightly modified. Perhaps in the future technology could be modified or improved to fit this new possibility, or new techniques could be introduced in the process of aural rehabilitation to help people localize more creatively, but equally effectively.
A broader application raises the question of the importance of localization in general, but if you’re asking why localization matters, you probably have not needed to live without it. It affects everything you do without you even consciously thinking about it. Examples include classroom learning environments, crossing the street safely, interacting with people in noisy environments, and so many other things. It would make sense to assume people just couldn’t survive without localization. The real phenomenon here is that some people do. But more on that later.
Daria Genzel, Michael Schutte, W. Owen Brimijoin, Paul R. MacNeilage, Lutz Wiegrebe. Psychophysical evidence for auditory motion parallax. Proceedings of the National Academy of Sciences, 2018; 201712058 DOI: 10.1073/pnas.1712058115
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