You Must Have Super Hearing

The short answer is “absolutely not.” The more complete answer is a little more complicated.

What the audiologists say. Most of us will experience presbycusis, or age-related hearing loss. We’re not exempted from this happening just because we’re blind. In the last fifteen years or so I’ve lost about 8% of the hearing in my left ear and 4% in my right ear. So, not only do I not have super hearing, my hearing is below normal.

Of course, you experience all of the other problems that anyone else encounters when their hearing deteriorates. But, because your hearing is more critical if you’re blind, the consequences of hearing loss are even greater. You depend, for example, for very subtle auditory clues to detect when the person you are talking to has subtlety changed their position, maybe slightly to the right or a little to the left. Sometimes detecting these very minute sounds is impossible even with perfect hearing, but it becomes vastly more challenging with just the slightest hearing loss.

Concentration and distraction. So why is it then that so many people assume that someone who is blind must have super hearing? I suspect the answer is relatively simple. All it takes is to be in a situation in which the blind person notices something they’ve heard that you didn’t. “How did you know the dog is in the back yard? I can’t believe you heard that car in the next block; I didn’t hear a thing.”

It’s not that their hearing is automatically better than yours. In fact, if it were to be measured by a professional, it might not even be as good. It seems better because their brain is not having to process all of the visual stimuli yours is.

Think of the last time you laid awake trying to get to sleep. You might have heard the refrigerator in the kitchen cycle on and off, the neighbor pull into his driveway after a night on the town, and a dog barking in the next block. There’s a good chance that, if those same sounds had happened in the middle of the day, you might not have noticed them because of all the visual stimuli that were competing for your attention. Your hearing isn’t any better; it’s just that, without those distractions and without any additional effort on your part, these background sounds are more obvious.

Neuroplasticity. Here is where it gets a little more complicated and, I think, a lot more interesting. Years ago, neurologists believed that the brain was like a computer with the various portions fixed in place. Because of the development of functional magnetic resonance imaging (FMRI), it has become possible to look at the brain in real time. That is, researchers can now see how stimuli alter the brain minute-by-minute. One of the things they’ve learned is that the parts of the brain that perform specific tasks (think math, hand-eye co-ordination, etc.) expand or contract based on how often, and how intensely, they perform the task, what they call neuroplasticity.

Blind people, whether they’ve had vision and lost it or never had vision at all, are especially tempting subjects for these studies. Scientists know that, through prolonged and repeated experience, the brains of both children and adults can form new neuronal pathways and increase the portion of the brain that is devoted to a specific task. For example, the part of the brain that processes tactile stimuli is larger for Braille readers. In addition, after ten months of repeated practice, researchers found that Braille readers had created new neuronal connections in portions of the brain not normally associated with reading.

Similar results have been found with regard to the hearing of blind subjects. That is, the portion of the brain devoted to processing visual cues actually shrinks from lack of use, the portion devoted to processing sound increases, and the brain establishes new neuronal pathways to help with the transition. This doesn’t make for super hearing, but it does help make hearing more efficient. Now, if I could only tune-out the rap “music” at the mall.

Comments

  1. Linda Attanasio says:

    Good one John!
    Well written and a great explanation. I get comments like this a lot in the itinerant vision world.

  2. Angie Irick says:

    Good explanation! Now if you can explain why people ask a blind person if they know sign language we will have all of the answers we need. Smile!

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