Brain impulse that makes us quit identified

A team at Duke University says that the impulse which told ancient foragers to give up on one pasture and move on to more fertile hunting grounds is the same as that which urges people to try a different internet site if our initial choice is taking too long to appear on screen.

The scientists found that a section of the brain called dorsal anterior cingulate cortex (ACC) is responsible for weighing up reward against cost in any given situation.

When a certain threshold is reached, the brain gives a signal to throw in the towel, a newspaper reported.

For their study, the scientists analysed rhesus macaques monkeys. They observed whether the monkeys decided to stay with a food source giving ever smaller squirts of fruit juice or move to a newer and potentially better supply.

They studied a set of neurons within the animals` ACCs, which showed increasing activity as time passed. Once it reached a certain threshold the monkeys immediately moved on.

Lead scientist Prof Michael Platt said: "It is as if there is a threshold for deciding it`s time to leave set in the brain."

The scientists also factored in the time it would take to travel to the next food source and when this was increased, it took longer for the "quit" threshold to be reached.

Prof Platt said that the findings tallied with a 1976 evolutionary theory, the Marginal Value Theorem, which stated that foragers would stay longer at a blackberry bush as the distance between bushes became greater.

The idea has been shown to hold true across the animal kingdom in worms, bees, fish and seals. Prof Platt said: "This is a really fundamental solution to a fundamental problem."