At this point, we have all the scientific information we need in order to prevent the surgings of the coronavirus: Avoid gathering indoors with people from outside your household, keep physically apart from others, wear a mask, wash your hands often. Among those who can follow these precautions — a lot of people, as policymakers should recognize, can’t afford to — too many are still disregarding public health advice. A recent report by researchers from Northeastern University and elsewhere found that the number of Americans heeding most recommendations has dropped steadily since April. (Mask-wearing, which has increased, was an exception.)

This is a problem that societies have wrestled with for centuries: How do you persuade people to do things that are beneficial to the community, like social distancing — or crucially, being vaccinated when the time comes — if such actions don’t immediately benefit those who take them or even put them at a disadvantage in some way? As it turns out, research suggests that we are more likely to engage in “prosocial behavior” if we think lots of others are doing so, too. But that creates an obvious conundrum: How can you persuade more people to adopt a new behavior if, to do so, it needs to already seem ubiquitous?

In 2008, The Journal of Consumer Research published what has become a classic study that showed how describing “social norms” to people — that is, telling them what a majority of others are doing — can encourage prosocial behavior. Robert Cialdini, then a professor of marketing and psychology at Arizona State University, and his colleagues conducted a series of experiments to explore how hotels could get more visitors to reuse their towels, thereby conserving resources (and boosting a hotel’s bottom line). Typically, washroom signs informed guests that the reuse of towels would help protect the environment. But the researchers wondered whether learning that lots of other people reused their towels would prove even more motivational.

To find out, they had the hotel leave the usual sign on the washroom towel racks of one group of rooms — the sign emphasized that reusing towels was environmentally friendly — and gave another group of rooms signs with the additional information that “almost 75% of guests who are asked to participate in our new resource savings program do help.” This second group turned out to be more than 25 percent more likely to reuse their towels. “Seeing what many others are doing lends itself to imitation,” Cialdini says. “We think that gives us a clue to what is the most valid response, what is the objectively correct thing to do.”