Do As The Romans (Or Perhaps the Visigoths) Do

New research shows that prosocial behaviors are catching, but in what way?

Posted Jun 25, 2013

Since my daughter started daycare, my days of full health have fallen into steep decline. This haven for happy innocents must be at the epicenter of a disease network. When the world faces its next pandemic, I have little doubt that the daycare will be identified as ground zero.

social network

All is not negative, however. Studies have shown that good things can also spread, including positive emotions and – recently – prosocial and cooperative behaviors. In a paper just published in PLOS ONE, Jillian Jordan, David Rand and colleagues report a study in which people played a type of public goods game. In this game, participants could choose to make cooperative decisions that would benefit others or selfish decisions entirely for their own gain. Overall, they found that as cooperation increased among the people connected to a participant, the more likely it was that the participant would behave cooperatively as well. In other words, cooperation spread as if it was contagious. (Selfish decisions also spread, but let’s focus on the positive.)

The idea that behaviors are contagious is evocative. But the link between behavior and infection is a metaphor, and an imperfect one. Catching the flu is involuntary; a great deal of behavior is not. People make decisions about whether to smoke, how much to eat, drink and exercise, and whether they should help others. Behaviors spread because when we make decisions, we often use other people to guide our choices. To understand social influence – including when behaviors are likely to spread and when they will not – requires that we understand why people rely on others as guides.

The world is a complex and ambiguous place. A useful heuristic for thinking about how people make decisions in the face of complexity is that when they enter new situations, they ask themselves, “How does a person like me behave in a situation like this?” The question isn’t usually asked consciously, but people often find answers in the behavior of others. What do other people think is going on? What are folks like me doing?

This tacit question, which James March called the logic of appropriateness, sheds light on why and how behaviors spread through social networks. First, social influence is not blind imitation. People use other people’s behavior, which can be quite specific, to answer a broad question: what kind of person should I be here? As result, observation of specific behaviors can have broad effects – social influence is not just a case of monkey see-monkey do.

picking up oranges

picking up oranges (image from Kees et al., 2013)

Further, unlike many viruses, behaviors are not transmitted by exposure to just anyone. The logic of appropriateness is like a parochial version of the maxim “when in Rome, do as the Romans do”. But instead it’s “do as my kind of people do” – and your reference group can vary. Perhaps you see yourself as a Roman, or more like the Visigoths who sacked the city, or most similar to the tourists who flock there today. But American tourists or British ones? In each case, your behavior will be quite different. As a result, the spread of behavior through social networks is lumpy – moving fluidly within groups and slowing at their boundaries.

Keizer and colleagues conclude their paper with a piece of advice for cities that want to encourage the spread of orderly prosocial behavior: “don’t just keep it clean, but clean up when people can see it and display some sort of effort in doing so”. Unfortunately, the logic of appropriateness suggests that this advice may not be terribly effective. People are influenced by others they perceive as similar to themselves. Thus, although their decisions are shaped by ordinary fellow citizens, they may not catch the behaviors of city employees who are paid to clean up. In fact, when you see a clearly distinct group tidying the environment, it may signal that it is not appropriate for you to do so – that’s their job, not mine.

Overall, though, the message is an optimistic one. Cooperative and prosocial behaviors can spread, and if we’re thoughtful about the people with whom we identify, we are more likely to catch behaviors consistent with our own values. Unfortunately, when it comes to viruses, avoiding my daughter until she finishes daycare is not an option, so I have resigned myself to many more days of sniffles.


There are interesting nuances to both of the papers described here that I did not have space to elaborate. Conveniently, both are open-access, and I encourage you to check them out directly.

Copyright Dominic J. Packer, 2013. All rights reserved.