When people decide whether to make decisions that benefit the greater good at some personal cost, they tend to be more cooperative when they go with their gut than when they deliberate on the issue. Now, Yale researchers have provided greater insight into the processes that drive cooperation and determine how well people work together in everyday life.

Making use of data from 4,218 adult U.S. residents who participated in nine different social dilemma studies, as well as a smaller study involving 236 subjects, the research found that positive emotions — feelings of gratitude, for instance — promote cooperation, whereas self-control significantly reduces cooperation. Surprisingly, negative emotions did not significantly decrease cooperation, according to the findings, published in Plos One on Jan. 27.

“[Our work] helps to deepen our understanding of why people cooperate, which is fundamental to human society,” said David Rand, professor of psychology, economics and management at Yale and senior author of the study, in an email to the News.

June Gruber, professor of psychology at the University of Colorado Boulder and the other senior author of the study, said in an email that the results showing positive emotions as an important ingredient for cooperation were not surprising. From an evolutionary perspective, positive emotions serve a special role in building and maintaining vital social bonds, she explained. These emotions are a critical piece of the glue that ties humans together and helps people survive in social communities, she added.

In the studies, participants had to decide what amount of money to keep for themselves and what amount to share, with all the money in the shared pool being doubled and split evenly between participants. Seven of the nine studies involved groups of four participants, whereas the remaining two studies were two-player games. All were one-shot games, meaning that participants had no fear of suffering from consequences of their actions should they decide to be selfish.

In all the games, it was advantageous for each individual to keep as much money to himself, but it was better for the group if everyone decided to cooperate. By asking participants to write down their thoughts about how they made their decisions and by analyzing the data using a tool called the Linguistic Inquiry and Word Count, researchers managed to disentangle the contributions of the different cognitive processes. The LIWC is a text analysis program that categorizes words into one of 70 categories, which are meant to reflect individuals’ emotional and cognitive states.

People whose responses had more words in the “positive emotions” category were more likely to cooperate than those whose responses fell into the “inhibition” category.

“It is a very interesting study that sheds light on the psychological roots of cooperation,” said Joshua Greene, a professor of psychology at Harvard who was not involved in the study. Greene added that identifying positive emotion and inhibition was an important step towards understanding why some people are more cooperative.

According to the study’s authors, the next step will be to further pin down the specific positive emotions that make people more inclined to work together. In particular, the researchers hope to explore possible differences resulting from self-focused emotions like pride as compared to other-focused emotions like compassion.