A new study has shown that dopamine, which plays an important role in setting people's moods, might also have a part to play in people's decision making abilities.
Experiments have shown that altering levels of the chemical in the brain influences the decisions people make.
Previous research led by the University College London team had identified a signal in the brain linked to how much someone enjoyed an experience. They found that signal could in turn predict the choices a person made.
In the current study, researchers suspected that he signal was dopamine.
They sought to determine how people make complex decisions when their dopamine system has been tampered with.
During the study, 61 participants were given a list of 80 holiday destinations, from Greece to Thailand, and asked to rate them on a scale of one to six.
They were then given a sugar pill and asked to imagine themselves in each of 40 of the destinations.
They administered L-Dopa, a drug used in Parkinson's disease to increase dopamine concentrations in the brain, before asking them to imagine the other holidays.
They rated all the destinations again, and a day later they were asked where they would prefer to go, out of paired lists of holidays.
The extra dopamine gave people higher expectations when rating holiday options and that translated into the choice of trip they made a day later.
Study leader Dr Tali Sharot, from the Wellcome Trust Centre for Neuro-imaging at UCL, said humans made far more complex decisions than other animals, such as what job to take and whether to start a family, and it seemed dopamine played an important part in that.
"Our results indicate that when we consider alternative options when making real-life decisions, dopamine has a role in signalling the expected pleasure from those possible future events," BBC News quoted Sharot as saying "We then use that signal to make our choices," Sharot added.
The findings are published in journal The Current Biology.