Listen to part of a psychology lecture. The professor is discussing behaviorism.

Now, many people consider John Watson to be the founder of behaviorism.And like other behaviorists, he believed that psychologists should study only the behaviors they can observe and measure. They're not interested in mental processes. While a person could describe his thoughts, no one else can see or hear them to verify the accuracy of his report. But one thing you can observe is muscular habits. What Watson did was to observe muscular habits because he viewed them as a manifestation of thinking. One kind of habits that he studied are laryngeal habits. 

Watson thought laryngeal habits... you know, from larynx, in other words, related to the voice box... he thought those habits were an expression of thinking. He argued that for very young children, thinking is really talking out loud to oneself because they talk out loud even if they're not trying to communicate with someone in particular. As the individual matures, that overt talking to oneself becomes covert talking to oneself, but thinking still shows up as a laryngeal habit. One of the bits of evidence that supports this is that when people are trying to solve a problem, they, um, typically have increased muscular activity in the throat region. That is, if you put electrodes on the throat and measure muscle potential - muscle activity - you discover that when people are thinking, like if they're diligently trying to solve a problem, that there is muscular activity in the throat region.

So, Watson made the argument that problem solving, or thinking, can be defined as a set of behaviors - a set of responses - and in this case the response he observed was the throat activity. That's what he means when he calls it a laryngeal habit. Now, as I am thinking about what I am going to be saying, my muscles in my throat are responding. So, thinking can be measured as muscle activity. Now, the motor theory... yes? 

Professor Blake, um, did he happen to look at people who sign?I mean deaf people?

Uh, he did indeed, um, and to jump ahead, what one finds in deaf individuals who use sign language when they're given problems of various kinds, they have muscular changes in their hands when they are trying to solve a problem... muscle changes in the hand, just like the muscular changes going on in the throat region for speaking individuals. 

So, for Watson, thinking is identical with the activity of muscles. A related concept of thinking was developed by William James. It's called ideomotor action. 

Ideomotor action is an activity that occurs without our noticing it, without our being aware of it. I'll give you one simple example. If you think of locations, there tends to be eye movement that occurs with your thinking about that location. In particular, from where we're sitting, imagine that you're asked to think of our university library. Well, if you close your eyes and think of the library, and if you're sitting directly facing me, then according to this notion, your eyeballs will move slightly to the left, to your left, cause the library's in that general direction. 

James and others said that this is an idea leading to a motor action, and that's why it's called "ideomotor action" - an idea leads to motor activity.If you wish to impress your friends and relatives, you can change this simple process into a magic trick. Ask people to do something such as I've just described: think of something on their left; think of something on their right. You get them to think about two things on either side with their eyes closed, and you watch their eyes very carefully. 

And if you do that, you'll discover that you can see rather clearly the eye movement - that is, you can see the movement of the eyeballs. Now, then you say, think of either one and I'll tell which you're thinking of. 

OK. Well, Watson makes the assumption that muscular activity is equivalent to thinking. But given everything we've been talking about here, one has to ask: are there alternatives to this motor theory - this claim that muscular activities are equivalent to thinking? Is there anything else that might account for this change in muscular activity, other than saying that it is thinking? And the answer is clearly yes. Is there any way to answer the question definitively? I think the answer is no.