How is Dopamine Related to Pleasure?
The earliest experiments involving dopamine function were performed back in the 1950s and 1960s by a researcher named James Olds, who discovered that when rats' brains received a jolt of electrical stimulation in a certain area, they'd keep performing an action such a yanking a lever over and over [source: Chen].
Because dopamine played a role in transmitting the signals, scientists initially suspected that it had something to do with pleasure. People with clinical depression tend to have low levels of dopamine in their brains, which led researchers to hypothesize that low levels of dopamine caused a person to experience less pleasure.
That idea keeps bouncing around in the popular media, because it seems to make good sense. But by the late 1980s, it had been disproven by research. In experiments, animals whose dopamine cells were killed off by drugs still seemed to enjoy the taste of sugar when it was squirted into their mouths, as evidenced by their facial expressions. But they wouldn't seek out additional tastes of the sugar [source: Chen].
While dopamine doesn't cause pleasure, it does influence how pleasure affects the brain. But there are different views of how it accomplishes that. One school of thought is that dopamine's biggest influence is reinforcing the pleasure, so that the brain develops an expectation of experiencing that outcome from the action [source: Chen]. Research on gamblers, for example, have shown that their brains experience as much dopamine activity when they come close to winning as when they actually win. It's almost as if the chemical is urging them on, telling them that they'll win the next time (even if they didn't last time) [source: Chase and Clark].
Another view is that dopamine simply helps the brain to feel more motivated to do something so that the body feels energetic enough to pull that lever again and again [sources: Chen, Salamone and Correa].