Peripheral reaction time faster in deaf adults and sign language users

Excerpted from the April 2017 edition of AOA Focus.

For years, movies and comic books have entertained us with stories about sensory compensation. The blind superhero Daredevil navigates the criminal underworld with his enhanced senses. In "Scent of a Woman," sightless Al Pacino can identify the brand of soap a woman uses within moments of meeting her. While this may sound like Hollywood fodder, a recent study seems to show a clear example of sensory compensation among deaf adults.

Super vision

Scientists from the Academic Unit of Ophthalmology and Orthoptics at the University of Sheffield in England found that deaf subjects had significantly better reaction time to peripheral vision stimuli than subjects who could hear. 

"What they are showing is not that deaf people have a wider peripheral field; it's that their reactions are faster," says David Lewerenz, O.D., assistant professor at the University of Colorado Department of Ophthalmology and former chair of the AOA's Vision Rehabilitation Section (now Vision Rehabilitation Committee). "They are paying more attention to their peripheral vision. Having a wider field of vision would require a major reorganization of the eye and the neural processing." 

Dr. Lewerenz likens the phenomenon to bandwidth on a computer. With fewer "applications" (senses) using up the brain's processing power, more resources are in play for the remaining senses. The same is true for blind people who exhibit incredibly sensitive hearing. They cannot detect tones that are out of the range of typical human hearing; rather, their brains devote more real estate to analyzing the sounds they do hear.

Reading the signs

One interesting aspect of this study is that subjects who could hear and were fluent in sign language proved to have better peripheral reactions than subjects who could hear but were unfamiliar with sign language. (The deaf subjects exhibited faster reactions than both of the hearing groups.) 

"That part was a surprise to me. The sign language interpreters didn't do better than the deaf people, but did do better than normal-hearing people who weren't sign language interpreters. So that is obviously a learned skill," says Dr. Lewerenz. "Maybe they have learned to pay more attention to their peripheral vision so they can catch more information and use it in their interpreting." 

The lead researchers of the study point out that improving peripheral vision by studying sign language could be a boon to athletes who rely on peripheral vision in competition. However, Dr. Lewerenz is skeptical whether that is the best way to boost that skill set. 

"There are specific therapies that sports-vision optometrists use to enhance peripheral perception," he says. "I would guess those would be more effective than learning to be a sign language interpreter."