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 the button knocked out all the mice's normal behaviors was interpreted as dopamine creating such an intense rush of pleasure that it trumps the pleasure we get from food, drink, and sex.

"Dopamine creates pleasure" came to echo far beyond the narrow circle interested in brain chemistry. Through popular science books, newspaper articles, and even songs, dopamine became the brain's own super celebrity. A nerdy symbol of hedonism where T-shirts and tattoos with the chemical structure of dopamine signaled that life should be enjoyed.

But scientific truths need to be questioned from time to time and in the late 1990s, a series of discoveries were made that made scientists suspect that the widespread image of dopamine as a “pleasure chemical” was incorrect. In one of these trials, three individuals with deep and intractable depression had, as a last resort, electrodes implanted into the brain's reward center. The hope was that electrical stimulation would create intense pleasure and thereby break the paralyzing grip of depression. But when the power was turned on, the three individuals did not experience pleasure. Instead, something unexpected happened: they started planning for things they wanted to do. One told the surgeon that he decided to see Cologne's world-famous cathedral while in town (the operation was performed in Cologne). Another said she intended to resume bowling, a hobby she had not pursued in over a decade.

The activation of the reward center thus seemed to make them want to do things—see the cathedral or go bowling—without feeling better or experiencing positive emotions in general. Could it be that wanting and enjoying were not the same thing in the brain and that dopamine was more about wanting than enjoying?

A series of new experiments confirmed this was exactly the case. When the American neuroscientist Kenneth Berridge genetically manipulated mice so that they could not produce dopamine the animals stopped eating. Even though food was placed in front of their noses, they made no effort to reach for it. If the food was placed in their mouths, however, they ate and also seemed to think the food tasted good, a conclusion that can be drawn since the mice's faces had the same expressions as babies drinking sugar water (yes, mice have facial expressions too).

That mice whose brains don't produce dopamine don't want food but still enjoy it when they eat suggests that dopamine makes us want but it doesn't make us enjoy. That leaves us with a new question: what creates pleasure? Two decades of research have revealed the answer: endorphins. You want the juice because of dopamine. You enjoy it because of endorphins.

Why is this important? Because the dopamine system is extremely robust. It constantly steams on and leaves us wanting more. Endorphins, on the other hand, exert their effect on five small places in the brain which in medical language are called "hedonic hotspots." There are at least five such places scattered in different parts of the brain. One is found in the insular cortex, embedded in the temporal lobes; another part of the medulla oblongata called the pons. One is found in the part of the frontal lobes that sits directly behind our eyes and one is found in a small part of what is called the reward center. These five hotspots form a network. Pleasure is thus not found in one but several places in the brain.

While the dopamine system is powerful, robust, and easily activated, hedonic hotspots are fragile and sluggish. The brain therefore finds it easy to want—dopamine—but difficult to enjoy—endorphins. Most of us have personal experience of this. I don't think I'm alone in having spent more hours of my life intensely wanting things (more books! more guitars!) than enjoying them when I get them.

Among the most important things you can learn about your brain is that it doesn't just want what it enjoys, it wants things for the sake of it. Why we are built that way probably has an evolutionary explanation. If you did not constantly strive for new resources, you starved to death during 99.9% of human history. It therefore made sense that wanting is much stronger than liking in our brains. Discovering and seeing through this evolutionary hoax is among the most important things one can learn about oneself.

References

Berridge, K. et al (2015) Pleasure Systems in the Brain. Neuron 86, May 6;86(3):646–666.

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