Thursday, April 16, 2009

A Testament to the Flexibility of the Human Mind

I'm sure you've heard that humans have five senses: sight, hearing, touch, taste and smell. But we actually have far more senses than that. The canonical list doesn't include equilibrioception-- our sense of balance-- the result of fluid sloshing around in the inner ear. It also doesn't include proprioception, the ability to detect the position of our limbs using nerve endings in our tendons and muscles.

Furthermore, the sense of touch is actually several different senses, each detected and transmitted by its own special type of neuron. The sense of touch includes vibration sense, pressure sense, heat sense, cold sense and pain sense. The sense of smell can be divided into roughly 400 senses in humans, each one tuned in to a different class of airborne molecules. Vision can be divided into cells maximally responsive to four different wavelengths of light.
I could go on but the rest are less exciting.

This brings me to what I really want to write about, the development (or perhaps refinement) of a new human sense: echolocation. Echolocation is the ability to gather sensory information about your surroundings by bouncing sounds off of objects and listening to the echo that returns. It's what bats use to hunt in the dark, and dolphins use to navigate muddy water and find food under the sand.
There are a number of blind people who have developed the ability to use clicking sounds to "see" their surroundings, and it's remarkably effective. This represents a new use of the human mind, or at least a refinement of a rudimentary sense. Here are a few links if you'd like to watch/read more about it:

Human echolocation- Wikipedia
Daniel Kish- You Tube
The boy who sees without eyes- You Tube

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