What is Perception ?

Perception -- seeing, hearing, touching, smelling, tasting, feeling the positions of joints and the tension of muscles, balance, temperature, pain... -- begins with the stimulation of sensory neurons. Each sense involves highly evolved cells which are sensitive to a particular stimulus: Pain receptors respond to certain chemicals produced when tissues are damaged. Touch receptors involve cells with hairs which, when bent, cause signals to travel down the cell's axon. Balance, movement, and even hearing involve similar hair cells. Temperature sensitive neurons response to heat and cold. Taste and smell receptors respond to environmental molecules in the same way that other neurons respond to neurotransmitters. And the neurons of the retina respond to the presence of light or the specific frequency ranges of light we perceive as color.

But perception is more than just passive reception of information. Perception is an active process: Touch, for example, requires movement - something that nowadays we call "scanning." Touch includes information about you (e.g. your muscles, joints) as well as about what you are touching. We can say the same about hearing. We should really call it listening! The sound itself is intrinsically moving, of course - it is constantly changing. If it didn’t, we would stop hearing it!

And the same is true about vision. Vision involves constant movement - of our eyes, head, and body, or of the things we see or all of the above. The outer parts of our retina are particularly sensitive to motion, so when something comes into our field of vision, our attention is drawn to it. Even the fact that we have two eyes (binocular vision) is a kind of movement: The two views are slightly different, as if we had moved a few inches to the left or right. If we kept our eyes and the scene we are looking at perfectly still, everything would all become white!

We should also keep in mind that perception is not something done with the eyes or the ears or any specific sense organ. It is a multi-sensory, full bodied thing: "A one-year-old child standing on the floor of a room will fall down if the walls are silently and suddenly moved forward a few inches, although nothing touches him."