Listen to part of a lecture in a psychology class.

P: Okay, today I'd like to continue our discussion of the human nervous system. We've said that the nervous system is essentially a network of specialized cells called neurons. And we said that the primary function of neurons is to relay signals from one part of the body to another.

Now, neurochemicals are chemicals that are produced by the body that influence neuron function. One very important neurochemical is dopamine. Several decades ago, it was learned that dopamine is related to the experience of pleasure. For a long time, researchers theorized that dopamine actually produced pleasure. That's because researchers found that when the animals they studied received a reward or even simply anticipated a reward, a release of dopamine was triggered in their brain. So it was quite logical to think that it was dopamine that produced a sense of pleasure in animals when they obtain a reward.

Okay, but more recent research suggests that dopamine doesn't actually produce pleasure. Instead, it increases the expectation of pleasure, so the higher the level of dopamine in an animal's brain, the more pleasure the animal expects to get when it obtains a certain reward, whether or not the animal will actually experience pleasure when it obtains that reward is another story. The actual sensation of pleasure itself appears to be produced by other neurochemicals.

Okay, now that's in research animals, but it's thought that dopamine serves a similar function in the human brain. And we think dopamine may play an important role in human decision making. How might that work? Any ideas? John?

S: Hum... P: Okay, how do we make decisions? S: Uh... P: Okay, imagine yourself sitting in a restaurant. S: Okay. P: And you're trying to decide whether you want to have spaghetti or pizza. S: Okay. P: How do you decide? S: Well, I kind of imagine what it would be like to be eating the spaghetti, you know, how it would taste and smell? P: Okay. S: Then I imagine what it'd be like to be eating the pizza. P: Okay. S: Then I pick whichever one I think I'm going to enjoy the most. P: Okay! That's what we usually do! We picture our various options in our mind, and we estimate how we're gonna feel if we choose this option, and how we're going to feel if we choose that option.

And researchers now believe that what happens is the brain keeps a record of our past experiences of which experiences produce pleasure and how much pleasure they produced. And then when we're in the process of making a decision and we're picturing one of our options in our mind, if our brain associates that option with pleasurable experiences in our past, it's gonna release dopamine.

And what does the dopamine do? It gives us the feeling that choosing that option will result in a positive outcome. And that's the option we should choose. You ever have to make an important decision, and it's really complicated, and logically, it's really hard to figure out what to do? But you have this intuitive sense, this gut feeling telling you which course of action to take. Well, based on these research findings, I wouldn't be surprised if that was actually dopamine at work and I don't know about you, but when I get one of those gut feelings, I trust it, completely.

In fact, it turns out that dopamine may actually play a role in the survival of the human species. Any idea why that might be? Okay, well, let's think about it. The more pleasure we expect to get from something, the... S: Harder we'll try to get it?

P: That's right! And dopamine increases the amount of pleasure we expect to get from something. So it motivates us to make the effort we need to work hard to get it. In terms of species survival, what's the one thing humans need to survive? S: Food? P: Right! And dopamine helps motivate us to do what we need to do to get our food. And without dopamine? S: Maybe people wouldn't have been motivated to work for the food they need? P: That's right! Work isn't always fun, but because of dopamine and the expectation of reward that it produces, in this case, food, people are motivated to do things they might otherwise not want to do.