When it comes to picking sports teams in the playground, children have long opted for best friends instead of their most talented classmates.

But a study suggests that favouring friendship over merit doesn't necessarily damage chances of sporting success.

This is because children who are chosen by friends feel indebted and improve their performance, according to research.

Scientists studied 256 children aged six to eight and ten to 12 in nine schools who competed in teams in a game which involved bringing balls from one basket to another for 30 seconds.


They then had to choose which boy or girl they wanted to do the task with in the second round "for the benefit of the team".

Best friends were 30 to 45 per cent more likely to be selected than others.

"Children who are chosen by friends substantially increase their performance compared to non-friends," researchers said.

"A plausible explanation is that these children reciprocate the favour by increasing their effort."

The study, published in the Royal Economic Society's Economic Journal, was carried out in primary schools in Belgium by Michele Belot, from the Nuffield Centre for Experimental Social Sciences at Oxford University, and Jeroen van de Ven, from the University of Amsterdam.