- The UK-based winners cracked the brain's "reward centre"
- It influences your happiness, pleasure or motivation to do something
- But the system can go wrong turning people into addicts
Three UK-based scientists have won a prestigious prize worth 1m euros for studying the brain's reward centre.
Their work helps understand our drive to shop, eat or even land on the moon.
Reward is necessary for keeping us alive, but it can also spiral out of control leading to gambling and drug addiction.
Wolfram Schultz, Peter Dayan and Ray Dolan said winning The Brain Prize - the biggest in the field of neuroscience - was a "great honour".
Prof Schultz is planning a holiday with the family, but his co-winners are still trying to figure out how to spend their prize money from Denmark's Lundbeck Foundation.
Our lives are spent constantly making decisions - should I eat in that restaurant, where should I go on holiday, should I apply for a new job, should I keep reading this story or move on?
One of the winners, Prof Peter Dayan from UCL, told the BBC: "Reward is exactly how we optimise those choices."
The trio's work over three decades has unravelled the critical role of the brain chemical dopamine.
It triggers a set of brain cells to respond whenever there is a reward. And eventually the brain responds even in anticipation of the reward.
"This makes us go for more reward and individuals that have more reward have a higher chance of survival," said Prof Wolfram Schulz, at the University of Cambridge.
He added: "This is the biological process that makes us want to buy a bigger car or house, or be promoted at work."
Prof Dayan said: "Animals of all different sorts have to be able to predict things that are going to be good or going to bad and choose actions in light of those predictions."
But if things turn out better than expected then the reward system kicks in to drive us to repeat the same behaviour in the future.
So if a restaurant turns out better than we thought, the dopamine response in the brain is stronger and that is why we are more likely to go there again.
But as well as keeping us alive, the dopamine system can go horribly wrong.
It is very obvious in people with Parkinson's diseases who are treated with drugs to boost dopamine.
Prof Ray Dolan, from UCL, told the BBC: "It can often have very negative effects leading to excess gambling.
"I've had patients when treated with these drugs have resorted to gambling, often secretive, and this has resulted in the tragedy of them losing their entire life savings."
Other patients have suddenly developed compulsive shopping habits.
Obesity is another example of a reward system that is now damaging health.
Prof Sir Colin Blakemore, from the Brain Prize selection committee, said: "The implications of these discoveries are extremely wide-ranging, in fields as diverse as economics, social science, drug addiction and psychiatry".