Why Deaf People Have Enhanced Vision

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Why do many people who are deaf have enhanced vision? This question was on the minds of researchers at The University of Western Ontario, who have discovered an answer by studying cats.

Only cats and humans can be born deaf

Although it is not uncommon for animals, including humans, to lose their ability to hear at some point during their lifetimes, only cats and people can be born deaf. Therefore congenitally deaf and hearing cats were chosen as the subjects of the study led by Stephen Lomber, associate professor in the Department of Physiology and Pharmacology at the Schulich School of Medicine & Dentistry, and Department of Psychology in the Faculty of Social Science.

Lomber and his research team found a link between enhanced vision and reorganization of the area of the brain that is responsible for auditory input in congenitally deaf cats. Specifically, they discovered that the deaf have only two enhanced visual abilities: visual localization in the peripheral field and visual motion detection. What seems to occur is that the auditory part of the brain that would normally detect peripheral sound switches over to enhance peripheral vision.

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It is estimated that 4.4 percent of people who cannot hear were deaf at birth. The National Institute of Deafness and Other Communication Disorders states that 2 to 3 children per 1,000 born in the United States are born deaf or hard-of-hearing.

Lomber explained that “the brain wants to compensate for the lost sense with enhancements that are beneficial.” Therefore, people who are deaf “would benefit by seeing a car coming far off in your peripheral vision, because you can’t hear that car approaching from the side.”

Knowing why deaf people have enhanced vision may also help scientists better understand how cochlear implants can help deaf patients and possibly also help individuals who lose their hearing later in life. According to the Food and Drug Administration, about 41,500 adults and 25,500 children had received cochlear implants in the United States as of April 2009.

SOURCES:
Lomber SG et al. Nature Neuroscience 2010 Oct; doi:10.1038/nn.2653
National Institute on Deafness and Other Communication Disorders

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