Some pro-environment messages, such as those that encourage people not to litter, try to get people to take action by emphasizing why people don't participate in conservation efforts and how that inaction harms the environment. For instance, psychologist Robert Cialdini, PhD, often uses the example in his speeches of the 1970s "Iron Eyes Cody" public service announcement, which shows people tossing bags of garbage from their cars as a Native American chief, with a tear rolling down his cheek, witnesses the littering.

But such messages may provoke the opposite of what they intend, encouraging people to do precisely what advocates were trying to prevent, research shows. Psychologists' applied research finds that a more effective message might be one that depicts that most people are doing the conservation behavior--which encourages others to do it, too. They say that such findings--based on studies that span more than 30 years--offer important lessons for crafting pro-environment messages geared at changing the public's conservation behaviors.

"In social psychology, there's a large volume of research that [social] norms can guide and spur behavior," says Wesley Schultz, PhD, a psychology professor at California State University in San Marcos, Calif., whose research involves applying social psychology theories to environmental problems.

However, these descriptive messages--highlighting pro-environmental behaviors that many people already do--are uncommon in environmental campaigns. Instead, most pro-environment communications rely on less-effective "save the environment" messages, awareness campaigns that alert people to the severity of the problem and general education messages that inform people how they can help, Schultz says.

To craft more effective pro-environmental messages, psychologists have taken their experiments to the field, trying the messages in, for example, hotels and national parks. Here's some of their recent findings.

Normative messages

Researchers at Arizona State University (ASU) have once again documented the power of social norms in influencing behavior in a series of as-yet-unpublished experiments that urged hotel guests to reuse their towels. Cialdini, the Regents' Professor of Psychology, and psychology graduate students Noah Goldstein and Vladas Griskevicius examined whether guests would more often comply with signs that promoted descriptive norms rather than conventional signs that merely encourage guests to help save the environment.

In one study, they randomly assigned one of five cards in 260 guests' rooms that explained how reusing towels would conserve energy and save the environment:

  • "Help the hotel save energy," focusing on the benefit to the hotel.

  • "Help save the environment," emphasizing environmental protection.

  • "Partner with us to help save the environment," centering on environmental cooperation.

  • "Help save resources for future generations," highlighting the benefit to future generations.

  • "Join your fellow citizens in helping to save the environment," focusing on the descriptive norm.

The most successful message was the descriptive norm message, which stated that reusing towels was the norm for hotel guests. Forty-one percent of these guests reused their towels. Researchers found the least effective message was the one that emphasized the benefit to the hotel--leading to only 20 percent of guests reusing their towels--followed by signs that urged environmental protection and the benefit to future generations, which both led to about 31 percent reusing towels.

"If you're in a situation and not sure how to act, you are going to look to other people and the norms of that situation," Goldstein says about the findings.

In follow-up tests, Goldstein and Cialdini also found the descriptive norm sign to be the most effective.

Injunctive-proscriptive messages

Some studies show that highlighting what others are not doing is also an effective technique--an approach researchers call injunctive-proscriptive messages.

Patricia Winter, PhD, a research social scientist for the U.S. Department of Agriculture (USDA), has tested such messages in California's Sequoia and Kings Canyon National Park by evaluating the effectiveness of signs that encourage visitors to stay on established trails. Winter presented her findings during APA's 2005 Annual Convention in Washington, D.C., in August.

The sign with an injunctive-proscriptive message--"Please don't go off the established paths and trails in order to protect the Sequoias and natural vegetation in this park"--was the most effective, preventing 95 percent of people from going off-trail.

"'Don't do this' is the most direct route to gaining compliance," Winter says.

The least effective sign tested, leading to 18.7 percent veering from the path, was a message that made off-trail hiking appear like the norm: "Many past visitors have gone off the established paths, changing the natural state of the Sequoias and vegetation in this park." The worst off-trail use--30.9 percent--occurred when no sign was posted.

Cialdini reports similar results in a study in press: In the Petrified Forest National Park in Arizona, he found that fewer people stole petrified wood from the park when signs indicated the appropriate behavior in a situation and emphasized what others were not doing. The sign read: "Please don't remove the petrified wood from the park, in order to preserve the natural state of the Petrified Forest."

"This cautions that slight variations in messages seem to be powerful in having an impact on behavior, and it's important to pay attention to content and signage," Winter says.

Despite such findings, Winter found in a survey of environmental professionals that most believed positively framed messages encouraging the "do's" of behavior would be most effective.

Sparking change

Many psychologists are working to get their own messages out about how social psychology research can improve conservation communications.

"The potential of psychology to help the environment often goes unrealized," says Shawn Burn, PhD, psychology and child development professor at California Polytechnic State University, San Luis Obispo.

She and Winter--in conjunction with the USDA--developed a handbook for environmental managers in local governments, national parks and the like to use in developing scientifically sound pro-environment interventions. In the booklet, Burn encourages resource managers and community leaders to incorporate findings from social science research to remove barriers to pro-environmental behavior and gear interventions that further promote those behaviors--known as a community-based social marketing strategy. For example, the handbook provides guidelines on the design of persuasive messages and commitment strategies so that resource managers can create their own effective environmental interventions.

Similarly, Canadian environmental psychologist Doug McKenzie-Mohr, PhD, delivers workshops and training to communities to explain community-based social marketing strategies. He teaches that behavior change is most effectively achieved at the community level. For example, he encourages community leaders to use simple message prompts to encourage conservation behaviors, such as placing a sign next to light switches reminding people to turn off the lights after leaving a room in areas where community leaders have identified this as a problem. In his resource guides (available at www.cbsm.com), he suggests that communities hold focus groups, observe attitudes and behaviors among residents or conduct a survey to uncover potential barriers within the community to pro-environmental behaviors.

"We're finally making inroads, but it's taken a long time," Schultz says. "But we are now making the connections with real-world agencies and convincing them that psychology is relevant to the work they do."

For example, Schultz has been giving seminars, workshops and training sessions at environmental agencies on how social psychology can aid in environmental messages. Goldstein, Griskevicius and Cialdini are writing an article for the Cornell Hotel and Restaurant Administration Quarterly, a publication for the hospitality industry, about how hotel managers can better persuade guests to reuse their hotel towels to conserve energy.

"Many community organizations want to change behaviors and want to create specific actions from viewers," Schultz says. "But they don't have the psychological research knowledge to integrate the basic principles that we know in psychology."

That's why Schultz says psychologists need to help make community leaders and environmental managers aware of the research so they can craft more effective messages.

Members of APA's Div. 34 (Population and Environmental) and researchers from the Brookfield Zoo in Brookfield, Ill., are launching a Web site, www.conservationpsychology.org, that includes profiles of many environmental psychologists' research and work.