One in three people born stubborn (and if you don't agree, tough)

IT COULD explain the extreme behaviour of the stubborn and bull-headed among us and is a trait displayed by great historical figures.

Now scientists say they have pinpointed a gene – held by an estimated one-third of the world's population – which is nature's way of ensuring that some people keep on trying when the rest of us give up.

Researchers at the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig say such influential figures as Lord Nelson, Winston Churchill and suffragette leader Emily Pankhurst probably had the "never say die" gene which gives them the dogged determination to continue in times of adversity.

Dr Tilmann Klein, one of the authors of the study, commented: "Where would we be without those few individuals who refuse to accept defeat and who continue to soldier onwards when common sense tells the rest of mankind that there's no use trying?"

The study's co-author, Dr Markus Ullsperger, said that about 30 per cent of the population have the so-called A1 mutation.

The researchers say this leaves people with fewer D2 receptors in the brain – activated when levels of the neurotransmitter dopamine drop.

The scientists believe that a lower output of dopamine – which is responsible for signalling fun and pleasure in the brain and also helps learning – means that some people are simply not satisfied when a decision or action turns out to be a "mistake". So, being obstinate, they repeat their actions.

People with more D2 receptors in their brains are satisfied the first time around that a mistake is a mistake. They do not feel any desire to repeat their actions.

The researchers studied 26 men, 12 of whom had the A1 gene mutation signalling low numbers of D2 receptors.

The subjects were shown sets of two symbols on a screen, and were asked to select one. The choice was followed by either a smiling face or a frown flashing on the screen.

The researchers then tested to check whether the men had learnt to choose the symbol that was the most positively reinforced and avoid the one that was the most negatively reinforced.

According to results of the study, published in the journal Nature, they found that men with fewer D2 receptors had trouble avoiding repeating their mistakes.

Brain imaging then was used to confirm that a region of the brain called the rostral cingulate zone was involved in learning from mistakes.

The hippocampus, a part of the brain which is key in forming memories, was also more active in the volunteers with normal D2 levels.

Dr Klein said: "The fact that nearly 30 per cent of the population has this A1 mutation, means we can only surmise that A1 must offer some genetic advantages.

"Some individuals persist even in the face of negative feedback, and doggedly persevere as long as it takes until they finally succeed."