In this game, I’m in a team of four people in different locations. Each of us is given the same amount of money. We are asked to choose how we will contribute to a group pot on the understanding that this pot will be doubled and split equally among us. Like all cooperation, this relies on a certain level of trust that the others in your group will be nice. If everybody in the group contributes all of their money, all the money gets doubled and redistributed four ways, so everyone doubles their money. Win–win!

“But if you think about it from the perspective of an individual,” says lab director David Rand, “for each dollar that you contribute, it gets doubled to two dollars and then split four ways – which means each person only gets 50 cents back for the dollar they contributed.”

In other words, even though everyone is better off collectively by contributing to a group project that no one could manage alone (in real life, this could be paying towards a hospital building, for example), there is a cost at the individual level. Financially, you make more money by being more selfish.

Rand’s team has run this game with thousands of players. Half of them are asked, as I was, to decide their contribution within 10 seconds. The other half are asked to take their time and carefully consider their decision. It turns out that when people go with their gut reaction, they are much more generous.

“There is a lot of evidence that cooperation is a central feature of human evolution,” says Rand. “In the small-scale societies that our ancestors were living in, all our interactions were with people that you were going to see again and interact with in the immediate future.” That kept in check any temptation to act aggressively or take advantage and free-ride off other people’s contributions.

So rather than work out every time whether it’s in our long-term interests to be nice, it’s more efficient and less effort to have the basic rule: be nice to other people. That’s why our unthinking response in the experiment is a generous one.

But our learned behaviours also can change.

Usually, those in Rand’s experiment who play the quickfire round are generous and receive generous dividends, reinforcing their generous outlook. But those who consider their decisions for longer are more selfish. This results in a meagre group pot, reinforcing an idea that it doesn’t pay to rely on the group.