In the early 2000s, visitors to Arizona’s Petrified Forest National Park were greeted by a sign imploring them not to steal irreplaceable pieces of fossil trees. “Your heritage is being vandalized every day by theft losses of petrified wood of 14 tons a year,” read the sign, “mostly a small piece at a time.”

Not the smoothest wording, perhaps, but at first glance it seemed to get the point across. Or did it? Robert Cialdini, a psychologist at Arizona State University who was fascinated by how people make decisions, had misgivings. He asked park officials to try an experiment. Researchers would distribute secretly marked pieces of petrified wood along paths, then count how many were stolen after weekends on which visitors were met with alternative signs.

One sign read, “Many past visitors have removed the petrified wood from the park, changing the natural state of the Petrified Forest,” and was accompanied by a picture of three visitors taking wood. Another read, “Please don’t remove the petrified wood from the park, in order to preserve the natural state of the Petrified Forest,” accompanied by a picture of one visitor taking wood with a circle-and-bar symbol superimposed over his hand.

The differences seem subtle, but the results were profound. Visitors who saw the first message took nearly five times as many fossils as visitors who read the second. (1) The reason, explained Cialdini, was because each sign conveyed a different social norm. The first sign emphasized the frequency of theft. Rather than discouraging unwanted behavior, the message normalized it. If everyone else is doing it, why shouldn’t I?

The story of Cialdini’s signs became a parable of how social influences shape choices—a phenomenon that’s widely recognized now, but at the time had yet to suffuse public consciousness. Over the past decade, a steady stream of social psychology, cognitive, and behavioral economics research has revealed us as mentally quirky creatures; our behavior flows only intermittently from knowledge, and our choices reflect not just personal calculations but a host of subtle, almost instinctive, social considerations. After all, humans are extremely gregarious creatures, culturally and biologically fine-tuned for group living. Some researchers frame this self-reflection in terms of Stone Age lifestyles, but they could as easily follow those roots far deeper into evolutionary history. We were social long before we were human.

All this we know. The question, then, is whether we can harness these tendencies to help solve problems such as climate change, environmental exploitation, and biodiversity loss. These are problems that our other cognitive traits—difficulty with abstractions, the tendency to ignore what’s not immediately tangible, a predisposition to exploit the commons for personal gain—compound with interest. In short: Can our social habits of thought be hacked for planetary good?

Among the approaches being studied by scientists, one of the most promising involves so-called descriptive norms, or how social expectations are framed and perceived. Cialdini’s petrified wood experiments are one example. In another classic experiment, Cialdini and colleagues altered the language of hotel-room placards urging guests to save water by reusing their towels; placards combining an environmental message with a mention of how most guests at that hotel reused towels were more effective than an environmental message alone. When the researchers tweaked the placard to say that most previous guests in that room reused towels, it was more compelling still. (2)

That latter observation was especially intriguing, hinting at how even a casual affiliation—people who happened to stay in the same hotel room at different times—could shape behavior. Yet further iterations of those experiments would show just how complex the effect can be. Another research team found that norms had little power on their own; to be effective, they needed to be paired with strong language about the importance of conservation. The guests-in-this-room appeal didn’t work at all. (3) A study conducted in two Alpine hotels rather than in the US, where the first norm-tweaking towel research was conducted, found the guests-in-this-room message superior to guests-at-this-hotel—but neither was significantly more effective than a standalone environmental message. (4) Another study, this time in Germany, favored the at-this-hotel message rather than the in-this-room one. Both norms, however, inspired less towel re-use than the standard environmental message. (5)

That the studies pointed in such divergent directions shouldn’t be discouraging. Rather, they underscore what remains to be learned together with the importance of accounting for different contexts and backgrounds. In western Europe, resource conservation values are already so established that additional appeals to those norms may make little difference.

Other sorts of social appeals have been more straightforward: in the aftermath of droughts in the southeastern US, residents of Cobb County, Georgia, reduced their water consumption after receiving a notice that compared their own use to that of their neighbors. (6) The comparisons were especially effective in reaching affluent, high-use households who would have ignored fee-based attempts to curtail their consumption. In a similar vein, telling people about their neighbors’ electricity use reliably reduces their own use, and their newfound habits remain even after the comparisons cease. (7) Complications do arise. People who learn that their neighbors are energy hogs may increase their own consumption, and political ideology can magnify or blunt a comparison’s effectiveness. As a rule, however, the effects are positive. (9, 10)

A newly encouraging wrinkle on the power of social norms involves a sense not just that other people are doing something, but that it’s a trend. In a recent study led by Stanford University psychologist Gregg Sparkman, researchers told diners at a school café that people are starting to eat less meat; these subjects were twice as likely to go meatless than diners informed that people are eating less meat. (10) Several variations of that experiment returned similar results. Further iterations may well reveal nuances, as in the case of hotel-towel placards, but it seems that trendiness has a certain power.

Crucially, that power was evident in Sparkman’s experiments—even though the behavior in question trended only among a small minority. Which is reassuring: after all, if people needed to feel that a great many others were changing before altering their own behavior, it would be difficult to upset a status quo. Just a small swing in social momentum may be enough.

1. Cialdini RB. Crafting normative messages to protect the environment. Current Directions in Psychological Science. 2003.

2. Goldstein NJ, Cialdini RB, and Griskevicius V. A room with a viewpoint: Using social norms to motivate environmental conservation in hotels. Journal of Consumer Research. 2008.

3. Schultz WP, Khazian AM, Zaleski AC. Using normative social influence to promote conservation among hotel guests. Social Influence. 2008.

4. Reese G, Loew K, Steffgen G. A towel less: Social norms enhance pro-environmental behavior in hotels. Journal of Social Psychology. 2014.

5. Bohner G and LE Schlüter. A room with a viewpoint revisited: Descriptive norms and hotel guests’ towel reuse behavior. PLoS ONE. 2014.

6. Ferraro PJ and Price MK. Using nonpecuniary strategies to influence behavior: Evidence from a large-scale field experiment. The Review of Economics and Statistics. 2013.

7. Allcott H. Social norms and energy conservation. Journal of Public Economics. 2011.

8. Clayton S et al. Psychological research and global climate change. Nature Climate Change. 2015.

9. Costa DL and Kahn ME. Energy conservation “nudges” and environmentalist ideology: Evidence from a randomized residential electricity field experiment. Journal of the European Economic Association. 2013.

10. Sparkman G and Walton GM. Dynamic norms promote sustainable behavior, even if it is counternormative. Psychological Science. 2017.

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Brandon Keim is a freelance journalist specializing in animals, nature and science, and the author of The Eye of the Sandpiper: Stories From the Living World. Connect with him on Twitter, Instagramand Facebook.