Sunday, February 18, 2007

Our 5+ senses

How many senses do we have?

According to our
folk psychology
(which is the commonsense understanding of human minds we uses day-to-day) we have five. One of our senses is so obvious that we don't even notice it as a sense at all-- our perception of where our body parts are. This is called
proprioception. So we have at least six senses. Some unfortunates can lose their proprioception and have a very difficult time controlling their bodies. Imagine if the only way you knew where your feet or hands were was by looking. Imagine walking, typing, or eating.

But the sense of touch is a strange one too. What we call touch is actually a bunch of distinct perceptual systems called the
somatosensory system, which has different sensors for things like pain, pressure, and temperature. At a deeper level of analysis all of these are separate senses too.

Pain itself is an interesting one. Certain drugs make one still feel the pain but not mind it. Only after the drug completely sets in do you not feel the pain sensation at all. This is interesting to me, as a cognitive scientist, because it suggests that there are separate "detectors" in the mind for 1) the recognizable "feeling" of pain, and 2) something actually "hurting!"

Even the visual system is not so simple. Turns out there are separate neural pathways in the brain that detect "what" things are, and "where" things are. People with certain kinds of brain lesions can have one knocked out and not the other. Can you imagine knowing where things are, but not being able to tell what they are? Or, even weirder, the opposite.

The point of this article is that how many senses we have has a different number depending on what level of analysis we are looking at. In our everyday talking, it makes sense to talk about the five or six, but when talking about known neural pathways and detectors in the mind, we get different answers. And that's okay.

As my man Marvin Minsky says, words should be our masters, not the reverse.

1 comment:

Cue said...

fascinating if true... :-)