A new study has revealed the role of the brain chemical dopamine in making decisions which give immense joy, like going on an holiday or plans to start a family.
It also contributes to an understanding of how pleasure expectation can go awry, for example in drug addiction.
"Humans make much more complex decisions than other animals - such as which job to take, where to go on holiday, whether to start a family - and we wanted to understand the role of dopamine in making these types of decisions," said lead author Dr Tali Sharot, Wellcome of Trust Centre for Neuroimaging at UCL.
"Our results indicate that when we consider alternative options when making real-life decisions, dopamine has a role in signaling the expected pleasure from those possible future events. We then use that signal to make our choices," Sharot added.
Dopamine is a neurotransmitter produced in several areas of the brain and is found in a wide variety of animals. Its role in reward learning and reward-seeking behavior is well established by animal studies - however, in humans its role is much less understood.
During the study, researchers examined the estimated pleasure of future events before and after the administration of a drug called L-DOPA, which is known to enhance dopamine function in the brain and is commonly used to treat patients with Parkinson's disease.
The 61 study participants were asked to rate their expectations of happiness if they were to holiday at each of 80 destinations, from Thailand to Greece. They were then given L-DOPA or a placebo and asked to imagine holidaying in those destinations.
They found that ratings for particular destinations increased after they were imagined under L-DOPA's influence. That increase also affected the participants' selections the following day.
"We had reason to believe that dopamine would enhance expectations of pleasure in humans, but were surprised at the strength of this effect. The enhancement lasted at least 24 hours and was evident in almost 80 per cent of the subjects," Sharot added.
The study is published in journal Current Biology.