More Friends, More Germs: How Disease Concerns Shape Our Social Circles
– by Soyeon Choi
Much of the research on friendship focuses on its benefits. Friends are a major source of support, and people with closer, more supportive friendships tend to report better health and well-being. But friendship also has costs, including one that is easy to overlook: time spent with other people is also time spent exposed to their germs. Over evolutionary history, when infection could be deadly, a larger social circle likely meant both more support and more exposure.
This raises a simple question: do people who are more concerned about germs build different kinds of friendship networks? Our starting point was the behavioral immune system, the set of psychological responses that helps people avoid possible sources of infection before the body’s biological defenses have to respond. People vary widely in how reactive this system is. Some are highly germ-averse, readily bothered by uncovered sneezes or shared surfaces. Others hardly register such things.
We expected germ aversion to track how many friends a person keeps, but not evenly. Friendship is layered. Most people have a small number of very close friends, a somewhat larger group of close friends, and then wider circles of casual friends and acquaintances. These outer circles can be valuable, but the benefits of each additional tie are often less certain than the benefits of a close friend. Because of that, we expected germ aversion to matter most for the looser, more casual parts of the network.
Across four studies involving 2,266 participants, mostly in the United States but in one case across six countries on four continents (Brazil, Germany, Ghana, India, Kenya, and the Philippines), that is broadly what we found. People who were more wary of germs reported having fewer friends overall, and this pattern was especially clear among casual friends and acquaintances rather than close friends. The strength of the association also varied across countries, presumably due to differences in social norms, disease ecologies, and expectations around friendship.
Was this about what people felt they needed, or what they actually wanted? It was both. People higher in germ aversion believed they should have fewer friends and preferred fewer friends, particularly in the outer layers of the network. For many germ-averse individuals, then, a narrower network seems to reflect both perceived health needs and personal preference.
The same selectivity showed up in what germ-averse people expected from the friendships they did keep. They tended to hold higher and more fixed standards for friendship, especially when it came to what friends could do, whether they were similar, and whether they could provide practical help. When social contact feels costly, each friendship may need to “earn” its place more strongly. This selectivity also appears to be specific to friendships. In supplemental analyses, germ aversion was not associated with the number of family members or coworkers a person had. This makes sense: friendship is one of the more flexible parts of social life, a relationship category where people have more room to decide whom to keep close, whom to see less often, and which ties are worth maintaining.
Finally, we tested whether the perceived relationship between health and friendship goals can be shifted. Participants wrote about either the conflict between these goals, such as social gatherings increasing the chance of illness, or the ways the goals can support each other, such as friends helping someone recover when they are sick. Among people high in germ aversion, emphasizing harmony between health and friendship goals led to greater satisfaction with their friendships than emphasizing conflict. That is, seeing friends as part of staying healthy rather than as a threat to it appeared to ease the disease-related cost they attach to friendship.
Taken together, our findings suggest that germ aversion is not only about how people respond to strangers, crowds, or unfamiliar outgroups. It may also shape the ordinary social worlds people build and maintain day to day. As research on friendship continues to grow, we hope this work adds to the conversation by showing that the value of friendship is best understood alongside its costs, and that people differ in how they balance the need for connection with the need to feel safe and healthy.
