When I get this question it is usually because the person asking hasn't understood what hypnosis is really about. When you ask this kind of question you are implicitly suggesting that stupid people (whatever that is) can be hypnotized. The underlying assumption is that it is bad to be hypnotizeable, because it's a form of mind-control or manipulation. Since hypnosis is neither mind-control nor manipulation, bright people can easily be hypnotized. In fact, some hypnotists say that bright people are the best hypnotic subjects. This is the case because the hypnotic state of mind is utilized in learning, and since a "bright person" must be someone who is an excellent learner, it's more likely that such a person is a good hypnotic subject.

It's important to understand that every person with a normal functioning brain can be hypontized, and that it's not a matter about being bright or stupid. Often when someone claims that they cannot be hypnotized, it is simply because they don't know what hypnosis is. The interesting thing is, that if you claim you cannot be hypnotized, and you really believe it, it will become a self fulfilling prophecy. Hypnosis is a natural state that you enter many times each day, so of course you can be hypnotized using formal inductions, but if you decide that you don't want to be hypnotized, the hypnotist will not succeed.

While this is very good, and a healthy view on hypnosis, you should be aware of this when you go to a hypnotist. There is no point in wasting time or money with on hypnosis, if you believe that you cannot be hypnotized. So I would suggest that the first thing you do, if you have this kind of belief, is to confront your hypnotist with it. The hypnotist will then be able to help you to rid your mind of any misconceptions about hypnosis, and possibly enjoy great benefits from hypnosis. Being bright about hypnotism will therefore help you to enter the hypnotic state.