The players in the National Basketball Association in the USA rank as some of the highest earning sportspeople in the world. In the 2007-08 season the best paid of them received salaries in excess of $20 million (£13.5 million), and more than 50 members of the league had salaries of $10 million (£6.7 million) or more.

The 2007-08 season is interesting because that is when psychologists Graeme Haynes and Thomas Gilovich reviewed recordings of more than 100 NBA games, looking for occasions that fouls were called by the referees when it was clear to the players that no foul had actually been committed. Whenever a foul is called, the wronged player gets a number of free throws – chances to score points for their team. Haynes and Gilovich were interested in how these ultra-competitive, highly paid sportsmen reacted to being awarded free throws when they knew that they didn’t really deserve them.

Missed shot

These guys had every incentive to make the most of the free throws, however unfairly gained: after all, they make their living from winning, and the points gained from free throws could settle a match. Yet Haynes and Gilovich found that players’ accuracy from unfairly awarded free throws was unusually low. It was down compared to the free throw league average, and down compared to the individual players' free throw personal averages. Accuracy on unfairly awarded free throws was lowest when the player’s team was ahead and didn’t need the points so much. But tellingly, it was also lower than average when the team was behind and in need of points – whether honestly or dishonestly gained.

If players in one of the most competitive and best-paid sports can apparently be put off by guilt, it suggests to me that an instinct for fairness can survive even the most ruthless environments.