Hearing depends on the hand you are using

ScienceDaily reports on the press release from Georgetown University on a presentation at the annual meeting of the Society for Neuroscience 2012 (here). Peter Turkeltaub was the senior investigator. The research was looking at how the two hemispheres handle sound and the relationship between motor and perception processes.

They hid sounds in background noise and measured whether they were heard. Two changes were made: which hand was used to register hearing the sound and whether the sounds were rapidly changing (like consonants) or slowly changing (like syllables). When a subject was using their right hand, they heard the rapidly changing sounds more often than when they used their left hand, and vice versa for the slowly changing sounds.

Since the left hemisphere controls the right hand and vice versa, these results demonstrate that the two hemispheres specialize in different kinds of sounds — the left hemisphere likes rapidly changing sounds, such as consonants, and the right hemisphere likes slowly changing sounds, such as syllables or intonation,” Turkeltaub explains. “These results also demonstrate the interaction between motor systems and perception. It’s really pretty amazing. Imagine you’re waving an American flag while listening to one of the presidential candidates. The speech will actually sound slightly different to you depending on whether the flag is in your left hand or your right hand.

The result seems to fit with some theories about dyslexia (difference between hearing phonemes and syllables) and to that extent is not surprising. A little more surprising is the indication that a very general hemispheric dominance might be effected by which hand is in use at the time. Much more surprising is the idea that hemispheric dominance has an effect on the perceptions that rise to consciousness. There is still lots of surprises out there.

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