Munching a cheese sandwich is not just a tasty delight, but might also be a mantra to successfully negotiating that pay rise.
Psychologists at the University of Cambridge have revealed that cheese is a good source of the amino acid tryptophan, which is crucial to the manufacture of the brain chemical serotonin.
And, they say, people with high levels of this brain chemical have strong chances of succeeding in delicate negotiations affecting their own interests.
Revealing their observations during a study, the researchers revealed that the volunteers with low levels of serotonin were more likely to allow emotions rule their minds, and make decisions that harmed their long-term interests.
However, people with high levels of the chemical behaved in a more rational way, and put their own material advancement ahead of the short-term satisfaction of telling their boss exactly what they thought of them.
The researchers say that these findings cast light on why some people tend to over-react to a perceived unfairness, becoming angry and combative, when they have not eaten.
During the study, the serotonin levels in 20 volunteers aged from 20 to 35 were manipulated.
The researchers asked the volunteers to fast overnight, and then gave them a protein-rich drink in the morning.
About four hours later, the volunteers were requested to participate in a financial negotiation called the Ultimatum Game, which involves one player proposing to split a sum of money with a partner. If the partner accepts, both players receive their agreed shares, but if the partner rejects the offer, neither player is paid.
All the subjects participated in the game twice-once receiving a shake with tryptophan removed and once receiving a tryptophan-rich shake.
The researchers say that players generally tend to reject half of all offers of less than 25 per cent of the total stake because their anger at the perceived unfairness out weighs their interest in the cash.
However, the study showed that the rejection rate was about 80 per cent among participants with low serotonin levels.
"Our results suggest serotonin plays a critical role in social decision making by keeping aggressive social responses in check. Changes in diet and stress cause our serotonin levels to fluctuate naturally, so it is important to understand how this might affect our everyday decision making," the Independent quoted Molly Crockett of the Behavioural and Clinical Neuroscience Institute, who led the study published in Science Express, as saying.
The researchers have revealed that the amino acid tryptophan, which is crucial to the development of serotonin in the body, is present in most protein-based foods.
They say that cheese, meat, soya beans, sesame seeds, chocolate, oats, bananas, dried dates, milk, and salmon are major sources of tryptophan.