I Can’t See What You’re Saying

When the link breaks between sight and sound

by Dan Roberts, Editor-in-Chief
PBA Low Vision Resource Center

Why do we visually impaired people also seem to have trouble understanding speech? Do we really need people to speak louder to us, as they are often prone to do? The answer may come from recent findings at the University of Utah. A study reported in the journal PLOS ONE has shown that a phenomenon called the McGurk effect may be the cause.

Scottish cognitive psychologist Harry McGurk first identified a link between hearing and vision in the 1970s. And now, University of Utah bioengineers have pinned the cause on the way our brains process sound. By recording and analyzing activity in the temporal cortex, the researchers found that much of what we understand is perceived more through our eyes than through our ears.

This discovery may be of value to treatment of conditions such as dyslexia, and it may help scientists better understand how speech is developed in infants. But of more immediate importance to us is that it helps explain why we seem to have increased difficulty understanding speech as our vision declines.

When normally-sighted people converse in person, much of what they understand is visual. In other words, they are reading lips. Take away the visual input, however, and they may as well be talking on the telephone. And we have all experienced difficulty trying to relay information on the phone. Without vision, for example, the word “bat” could very well be heard as “vat” or “that”. That’s why NATO and Western Union developed phonetic alphabets for spelling words aurally (Alpha, Beta, Charlie, etc.).

The bottom line is, low vision people are not necessarily hard of hearing. It would be more correct to say we are phonetically-challenged. That places the responsibility on the speaker, who should enunciate clearly while speaking at an appropriate volume and slightly slower speed.

“I can’t see what you’re saying” now takes on another meaning, and we hope it will be understood by those with whom we converse.

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