Dopamine is the neurotransmitter everyone has heard of. Dopamine existed long—I mean really long—before there were humans. It can be traced back at least 600 million years in the history of life, making dopamine one of the oldest known molecules. Almost all animals, even insects, have dopamine in their brains. For humans and animals, it serves the same function: it makes us want. If you reach for a glass of juice on a hot summer day and see a fly swimming in the juice, it is the same molecule that makes you reach for the glass that caused the fly to fly into it.

But why are you reaching for the juice glass? Because it would taste good to drink, of course. Wanting and liking are experienced so intertwined that the words seem interchangeable. We want something because we like it. If we like something, we want it.

Because dopamine makes us want things, researchers long took for granted that dopamine also makes us enjoy when we get the object of our desire. In the 1960s, researchers surgically inserted an electrode into the brains of mice. This allowed the mice to activate their own dopamine system at the push of a button. The result was astonishing: they stopped eating and drinking, and completely lost interest in the opposite sex. All they did was push the button. That........

© Psychology Today