Is Wittgenstein a behaviorist?

Wittgenstein does indeed talk a lot about our behavior. Behavior is in fact the only way we can know other minds. For Wittgenstein, it seems that behavior shows that there is mental activity, i.e., thought, going on in someone else. Saying that the only way we can know others' mental states and private sensations is through behavior does not mean, however, that behavior is all that matters. That there is behavior means there must be some mental activity that has produced this behavior. The behavior is just a public expression of one's thoughts, sensations, etc.

This past Tuesday there was an article in the New York Times Science Times about baboons and how they think. The researchers set up various experiments in which they looked at the baboons' behaviors in response to different stimuli and events. The ways in which the baboons acted hinted at their inner thoughts, for example, a female looked around for her child after hearing a recording of its voice, and the other baboons looked toward the mother.

Our behavior is directly linked to our inner sensations, our private experience is indeed what shapes our public behavior. Yes, one can behave as if one were in pain, or sad, even without feeling these emotions. This is what we do when we lie or when we're acting. But the fact that we can often distinguish lies from real feelings, and acting from truly feeling, lends even further support to the idea that behavior directly exhibits our inner, private experiences. This is why so many actors practice Method acting, through which they essentially live like the character they're portraying in order to actually feel the characters' emotions and thoughts.

Behavior is part of our private experience, one can consider it as the public expression of that experience. Language is just another behavior, another way of expressing our private experience.