Babies as young as 15 months have a basic sense of what is fair and unfair, a study has revealed.

Infants in the study were able to differentiate between the equal and unequal distribution of food, showing an early awareness of fairness, scientists said. There was also seen to be a link between how sensitive the babies were to fair behaviour and whether they would be willing to share a favourite toy.

Jessica Sommerville, associate professor of psychology at the University of Washington, said: “Our findings show that these norms of fairness and altruism are more rapidly acquired than we thought.

“These results also show a connection between fairness and altruism in infants, such that babies who were more sensitive to the fair distribution of food were also more likely to share their preferred toy.”

The research, published in the journal PLoS ONE, involved showing two short videos to 15-month-old babies. In the first, a bowl of crackers was distributed between two people – first with an equal allocation of crackers, and then with one person getting more crackers than the other. The second video showed a jug of milk being shared between two people in a similar way.

Scientists measured how long each of the babies looked at how the food had been distributed, as babies pay more attention when they are surprised. They discovered that babies spent more time looking at the allocation of food if one person got more than the other.