Nudging environmental behavior

Would this grocery cart, outfitted with a reflection of your face, make you buy more produce? Recent research suggests it would.

Psychology Matters

We are remarkably social creatures, evolutionarily tuned to our local environments to an extent we rarely appreciate. Change someone’s environment, you changed their behavior.

Policies that ignore the nuances of human psychology, that assume Homo sapiens and Homo economicus are roughly the same beast, will never reach their hoped-for level of impact.

On the other hand, policy makers who engage with behavioral science will find low-cost, low-opposition measures that are often jaw-droppingly effective.


Nudging refers to effecting desired behaviors through subtle changes to the context in which the decision is made. No economic incentives, no requirements, just change the person’s environment, and… voila! It has been described as a sort of “libertarian paternalism” for policy makers: libertarian because it doesn’t impinge on anyone’s options, paternalistic for trying to change behavior for the greater good.

The New York Times recently highlighted interesting research on nudging consumers to healthier food purchasing decisions. Just putting a strip of yellow duct tape down the middle of customers’ carts and instructing them to put fruit and vegetables in one half, more than doubled the amount of produce the average customer bought. Putting a reflective placard in shopping carts also increased the amount of produce bought, as did informing customers of the amount of produce the average customer purchases. Interestingly, those three “tricks” all work through a different mechanism: The first by focusing attention on the amount of produce in the shopper’s cart and enlarging its space, the second by reminding the customer of his or her appearance and making the relationship between grocery choices and health more salient, and the third by activating social norms.

Each of those makes the customer aware that some sort of intervention is happening. But that needn’t be the case. Consider this: when you enter your grocery store, which direction do you turn? Usually, it’s to the right. But by putting big green arrows on the floor, the same researchers were able to direct 90 percent of shoppers to disregard their norms and habits and head left for the produce isle.

Clearly, nudges can effect powerful changes in behavior. However, they have to be implemented with an appreciation for nuance. When customers got both a reflective placard in the cart and arrows on the floor, they bought less produce.

Nudging for the Environment

Recycling rates can be increased by 34 percent simply by matching the shape of lid of the recycling bin to the shape of the object to be recycled: small circles for cans and bottles, slits for paper. The researchers’ proposed mechanism: Reducing the cognitive demand required leads to increased compliance.

Hotels have been able to nudge customers to reuse towels—saving money for the hotel and decreasing environmental impact without decreasing the quality of service for customers who want a fresh towel every day—by putting cards in bathrooms with messages like, “Help us preserve natural resources by reusing your towel.” Those sorts of messages though—aimed at rational and moral processes—appear to be less effective than social norm based messages. While the environmental messages generated 35 percent reuse, a social norm message like “75 percent of guests use their towels more than once” generated a 44 percent reuse rate.

The drive toward the social norm can push either toward or away from pro-environment behavior. When energy bills included a comparison to average use for the neighborhood, customers who had used more than average decreased their use, while those who had used less than average increased their use. However, when customers whose energy use was below average got a smiley-face with that news, the emoticon prevented the subsequent increase. And including a frowny-face with the news that a customer’s energy use was above average led to an even greater reduction than the comparison alone. Seriously, emoticons.

So as you go about your day, remember that every day, more people are doing what they can to protect our environment. Just like you. :-)

Further Reading

Thaler and Sunstein: Nudge: Improving Decisions About Health, Wealth, and Happiness.

Castelo: Behavioral Dimensions of Climate Change Policy.

Among many others.