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THE NEUROBIOLOGY OF “I WANT”
How does the reward system compel us to act? When the brain recognizes an opportunity for reward,
it releases a neurotransmitter called dopamine. Dopamine tells the rest of the brain what to pay
attention to and what to get our greedy little hands on. A dopamine rush doesn’t create happiness itself
—the feeling is more like arousal. We feel alert, awake, and captivated. We recognize the possibility
of feeling good and are willing to work for that feeling.
In the last few years, neuroscientists have given the effect of dopamine release many names,
including
seeking
,
wanting
,
craving
, and
desire
. But one thing is clear: It is not the experience of
liking, satisfaction, pleasure, or actual reward. Studies show that you can annihilate the entire
dopamine system in a rat’s brain, and it will still get a goofy grin on its face if you feed it sugar. What
it won’t do is work for the treat. It likes the sugar; it just doesn’t
want
it before it has it.
In 2001, Stanford neuroscientist Brian Knutson published the definitive experiment demonstrating
dopamine’s role in anticipating, but not experiencing, reward. He borrowed his method from a
famous study in behavioral psychology, Ivan Pavlov’s classical conditioning of dogs. In 1927, Pavlov
observed that if he rang a bell before feeding his dogs, they started to salivate as soon as they heard
the bell ring, even if food was nowhere in sight. They had learned to associate the sound of the bell
with the promise of dinner. Knutson had a hunch that the brain does its own kind of salivation when it
expects a reward—and, critically, that this brain response is not the same as the brain’s response
when the reward is received.
In his study, Knutson put human participants in a brain scanner and conditioned them to expect the
opportunity to win money when they saw a special symbol appear on a screen. To win the money,
they’d have to press a button to get the reward. As soon as the symbol appeared, the brain’s
dopamine-releasing reward center lit up, and the participants pressed the button to get their reward.
When the participants actually won money, however, this area of the brain quieted down. The joy of
winning was registered in different areas of the brain. Knutson had proven that dopamine is for
action, not happiness. The promise of reward guaranteed that participants wouldn’t miss out on the
reward by failing to act. What they were feeling when the reward system lit up was
anticipation
, not
pleasure.
Anything we think is going to make us feel good will trigger the reward system—the sight of
tempting food, the smell of coffee brewing, the 50-percent-off sign in a store window, a smile from a
sexy stranger, the infomercial that promises to make you rich. The flood of dopamine marks this new
object of desire as critical to your survival. When dopamine hijacks your attention, the mind becomes
fixated on obtaining or repeating whatever triggered it. This is nature’s trick to make sure you don’t
starve because you can’t be bothered to pick a berry, and that you don’t hasten human extinction
because seducing a potential mate seems like too much of a hassle. Evolution doesn’t give a damn
about happiness itself, but will use the promise of happiness to keep us struggling to stay alive. And
so the promise of happiness—not the direct experience of happiness—is the brain’s strategy to keep
you hunting, gathering, working, and wooing.
Of course, as with many of our primitive instincts, we find ourselves in a very different
environment now than the one the human brain evolved in. Take, for example, the flood of dopamine
we experience whenever we see, smell, or taste high-fat or high-sugar food. That dopamine release
guarantees we will want to stuff ourselves silly. This is a great instinct if you live in an environment
where food is scarce. But when you live in a world where food is not only widely available but also
specifically engineered to maximize your dopamine response, following every burst of dopamine is a
recipe for obesity, not longevity.
Or consider the effects of sexually graphic images on our reward system. For much of human
history, you weren’t going to see a naked person posing seductively for you unless the opportunity for
mating was real. Certainly a little motivation to act in this scenario would be smart if you wanted to
keep your DNA in the gene pool. Fast-forward a few hundred thousand years, and we find ourselves
in a world where Internet porn is always available, not to mention constant exposure to sexual images
in advertisements and entertainment. The instinct to pursue every one of these sexual “opportunities”
is how people end up addicted to X-rated websites—and victims of advertising campaigns that use
sex to sell everything from deodorant to designer jeans.
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