[music playing]

Narrator: We know that we can influence the way we feel by deliberately changing our brain chemistry. We do it all the time with drugs such as coffee, nicotine, and alcohol. Here in Chicago, one scientist has been experimenting with drugs.

Harriet De Wit: Drugs serve a very useful function in the study of emotion because they stimulate the very system that's activated in a natural situation when people go through an emotional situation. So we can use them as a tool to stimulate the limbic system.

Narrator: Harriet de Wit has devised a cunning experiment to test the effects of one drug, a stimulant, amphetamine.

Harriet De Wit: So here are your two envelopes.

Narrator: Two of the volunteers are told they've been given an inactive placebo pill. The other two, that they've be given a stimulant. In fact, all four have taken a dose of amphetamine. Drugs like amphetamine work by mimicking natural biochemicals in the brain. So if changes in biochemistry are all there is to experiencing an emotion, all the subjects should feel the same, whether they know they've taken a drug or not.

Half an hour into the experiment and the amphetamine begins to take effect. All the subjects will be experiencing an overall increase in arousal. They become restless. Tim and Ryan know they've taken a stimulant and are out of their seats already. But how will the unsuspecting Brooke and Mike react?

Harriet De Wit: We saw quite clearly that the people who were expecting to receive a placebo interpreted the sensations that they experienced quite differently. And they experienced them in a more negative way. They felt jittery. They felt anxious. They didn't enjoy the experience.

And in contrast, the people who knew that they were going to get a stimulant drug recognized and identified the sensations that they experienced as being due to the drug. And they actually enjoyed the drug effect. They felt energized. They felt focused. They talked more. They were amusing. So their behavior was really quite different. And each of their experiences of the effects of the drug were quite different, just simply depending on what they were expecting to receive.

Subject 1: I am a Gemini, born June 4, 1975. I am single.

Subject 2: I found a pebble on the floor, which has caught my interest.

Narrator: They're different responses reveal a great deal about the way subjective feeling is processed in the brain.

Subject 2: I'm trying to flick it up on my foot like a football.

Harriet De Wit: I think it tells us that the basic physiological responses that are involved in emotion are really only a part of the emotion. And what makes the experience that we describe as an anxious emotion or a positive emotion is very strongly influenced by the person's understanding of the situation and the person's interpretation of the situation.

Narrator: So even though they've all taken exactly the same drug, their experiences are quite different. The feeling of an emotion must be generated by something more than merely the presence of drug molecules in the brain.

[music playing]