Sharing Is Contagious

Sharing, as anyone who has worked with small children knows, is a skill that has to be taught. It’s not the most human tendency to fork over half a cookie, or a favorite toy, to a playmate. As we get progress through life, moving past those early formative years, what makes us more or less likely to share? A new study published in Current Biology sheds some light and found that it’s not our innate nature that determines how well we share, but the behavior of the group around us.

The study looked at the Hazda people in Tanzania, over a six-year period. Researchers were interested in this group because they need to get most of their calories in ways that are similar to how humans existed for much of our evolution; that is, by subsistence hunting and gathering. “They offer insight into how cooperation evolved,” wrote Ibrahim Mabulla, one of the researchers involved in the study. High levels of cooperation help a group like this, because it ensures survival when food sources are unreliable.

To study the Hazda’s interactions, 400 Hazda people in 56 camps in Tanzania were visited and asked to play a game involving straws of honey, their favorite food. The straws could be pooled as a group or kept for themselves. The researchers found that while you’d expect the game behavior to be the same across the board, Hazda people living in some camps were consistently more generous when playing the game than other camps.

“We were surprised to find that people do not have a stable tendency to cooperate and are instead influenced by those around them,” wrote the study’s lead author, Coren Apicella, Ph.D. She is an assistant professor of psychology and director of the Human Behavior and Origins Laboratory at the University of Pennsylvania. This challenges other evolutionary models for explaining cooperation, where there are “good guys” or bad guys” who have different dispositional types: cooperators and defectors. Instead, these findings show that human sharing behavior is more flexible and influenced by the people who surround us.

The cool thing about this study is that it means we can help others in our social circle become more generous and giving, simply by demonstrating this behavior ourselves.