So, you see, physical illness can have psychological causes. Now, we just have time to introduce another interesting example of the interaction between the mind and the body placebos. Placebos maybe you've heard them called sugar pills are harmless substances not always sugar that are used routinely on groups of sick people in experiments. These experiments test the effectiveness of new drugs. One group is given the new drug, the other group is given a placebo, and the results are measured. As you might guess, some of the people who receive the new drug get better. Surprisingly, however, some of the placebo group also get better. Why? Well, it's an interesting question, one which doctors can't quite answer. Some of the group may have gotten better on their own, without any treatment at all, but research has shown that the very act of taking a medication that you think will make you better, often does make you feel better. Have you even taken an aspirin and felt better in five minutes?