S HRIMP COCKTAIL , grilled sirloin with pear kimchi and chocolate lava cake. Donald Trump and Kim Jong Un had the same food brought to them on individual plates during their summit on February 27th. Psychologists think a meal like this is a good first step towards improving relations. But new work suggests there might have been a more positive outcome with a different serving arrangement.

As Kaitlin Woolley of Cornell University and Ayelet Fishbach of the University of Chicago report in Psychological Science, a meal taken “family-style” from a central platter can greatly improve the outcome of subsequent negotiations.

Having conducted previous research in 2017 revealing that eating similar foods led to people feeling emotionally closer to one another, Dr Woolley and Dr Fishbach wondered whether the way in which food was served also had a psychological effect. They theorised that, on the one hand, sharing food with other people might indicate food scarcity and increase a notion of competition. However, they also reasoned that it could instead lead people to become more aware of others’ needs and drive co-operative behaviour as a result. Curious to find out, they set up a series of experiments.

For the first test they recruited 100 pairs of participants from a local café, none of whom knew each other. In return for a $3 gift card and a chance to win $50 based upon their performance during a negotiation game, the participants were sat at a table and fed tortilla chips with salsa. Half the pairs were given their own basket of 20 grams of chips and a bowl of 25 grams of salsa, and half were given 40 grams of chips and 50 grams of salsa to share. As a cover for the experiment, all participants were told this snack was to be consumed before the game began.

The game required the participants to negotiate an hourly wage rate during a fictional strike. Each person was randomly assigned to represent the union or management and follow a set of rules.

The researchers measured co-operation by noting the number of rounds it took to reach an agreement, and found that those who shared food resolved the strike significantly faster (in 8.7 rounds) than those who did not (13.2 rounds). A similar experiment was conducted with 104 participants and Goldfish crackers, this time negotiating an airline’s route prices. The results were much the same, with the food-sharers negotiating successfully 63.3% of the time and those who did not share doing so 42.9% of the time.

To see if food-sharing among friends worked in the same way as it did among strangers, Dr Woolley and Dr Fishbach ran their strike experiment again with 240 people, partnering together two friends or two strangers. Regardless of whether the pairs were friends or strangers, those who shared food went into fewer rounds during the game, averaging 6.4 rounds, than those who did not share food, averaging 9.8. Friendship did have an effect, though. Whether they shared food or not, friends were generally more co-operative.

Mr Trump and Mr Kim might balk at having to take turns serving themselves from platters in the centre of a table. But these results suggest that such an arrangement really could help world diplomacy.