Oh, the humanity. Putting faces on social causes.

Back in the 1940s, the U.S. Forest Service began a public service campaign aimed at preventing forest fires. It featured Smokey Bear, a humanized caricature of a bear wearing blue jeans and a ranger’s hat. In a kind, gravelly voice, Smokey enlisted public support with slogans, his most famous being: “Remember—only you can prevent forest fires.” Smokey’s effort is considered one of the most enduring and effective advertising campaigns of all time.

I know the ads worked for me as a boy. I grew up in a heavily wooded area, and became extremely cautious about matches and campfires as a result of Smokey’s message, as did all my friends. But why were we all so responsive to these ads?  Was it the message of civic responsibility and public good? Fear of fire? Growing environmental awareness? Or was it Smokey himself, with his kind voice and sad eyes?

Ahn tested this idea in a couple simple laboratory experiments and one field study—all having to do with taking respo0nsibility for the environment. In one study, for example, she led volunteers to believe they were judging an energy conservation poster for the city’s electrical utility. Half the volunteers saw a picture of a light bulb that had been humanized with eyes and a mouth, which spoke these words: “I am burning. Turn me off.” The others saw the same light bulb, but without the human features and a less personal message: “Our bulbs are burning. Turn the lights off.”  Ahn then asked all the volunteers to indicate how likely they were to conserve energy, and the results were unambiguous. Those who had seen the humanized light bulb were much more likely to comply with the conservation campaign.

To verify and better understand this effect, Ahn ran another experiment, this one focusing on a food-waste recycling effort. It was similar to the first study, but in this one, some volunteers saw a garbage bin with a mouth and eyes and the caption: “Please feed me food waste.” The others saw an ordinary bin, with the caption: “Please put food waste in.” All volunteers then indicated the likelihood that they would separate food from other waste. They also completed a measure of their anticipatory guilt: That is, if they did not comply with the campaign, how guilty or ashamed would they feel?

The results were like before. Giving human features to the recycling effort boosted compliance, and what’s more, it clearly did so by inducing guilt feelings. Merely tweaking the garbage bin with a few simple humanizing changes was enough to make people anticipate feeling guilty, and change their plans to avoid this aversive emotion.

Plans are one thing, but how about real action. Ahn ran a final study, this one in a local coffee shop, to see if humanizing would boost actual donations to a cause. Customers who were settling up with the cashier saw a poster for a tree-planting campaign, called the Clean World Movement, placed next to a donation box.  Some saw a humanized tree, who pleaded: “Please save me and donate whatever you can.” Others saw an ordinary tree with the caption: “Please save trees and donate whatever you can.” Ahn unobtrusively recorded how many customers donated money to the cause, and how much.

The findings, reported in a forthcoming article in the journal Psychological Science, added additional, real-life, support for Ahn’s hypothesis. Most of the volunteers who saw the humanized tree gave at least some money. Significantly fewer of those who had seen the less personalized campaign made donations, and when they did, they gave much less money to the cause.

So it appears that simply humanizing light bulbs and trash bins is enough to stir up unpleasant feelings of guilt, which in turn makes people internalize abstract social causes. What’s more, such a social marketing strategy should be effortless. Indeed, the tendency to humanize non-human things–from cars to clouds to deities and bears–seems to be second nature.

*With colleagues Hae Joo Kim of Wilfrid Laurier University and Pankaj Aggarwal of the University of Toronto

Selections from Wray Herbert’s “We’re Only Human” blog appear regularly in The Huffington Post and elsewhere.