While some researchers are focusing on cultural influences on environmental beliefs and practices, others are trying to understand why individuals make decisions that help or hurt the environment.

One researcher who is studying green decision-making is Carmen Tanner, PhD, a postdoc in the Northwestern University laboratory of Douglas Medin, PhD. Before coming to Northwestern, she collaborated with Niels Jungbluth, PhD, an expert on the environmental cost of consumer products, on a study of how people choose environmentally friendly foods.

In their study, Tanner and Jungbluth found that people would consistently misjudge the environmental cost of food products. The direction and magnitude of the misjudgment depended on whether they were comparing the products to an environmentally ideal product--for example, a local, organically farmed, fresh vegetable--or to a product with a mix of environmentally positive and negative traits. But under none of the experimental conditions, says Tanner, were participants able to give an unbiased estimate of the environmental cost of the products they were choosing.

The findings suggest that even when all the information is available--which is rarely the case--people may not judge environmental costs correctly, and thus may not make the most environmentally friendly choices, says Tanner.

Tanner and Jungbluth's study, which was published in the Journal of Experimental Psychology: Applied (Vol. 9, No. 1), is just one example of a class of experiments aimed at understanding the individual psychology of environmentally friendly behavior.

Another example is recent work by Arizona State University psychologist Robert Cialdini, PhD. At APA's 2002 Annual Convention, Cialdini presented preliminary results from a study on the theft of natural objects from Arizona's Petrified Forest National Park. Despite signs posted around the park to remind visitors that removing petrified wood from the park is prohibited, an average of more than a ton is smuggled out each month.

In an experiment conducted in the park, Cialdini and his collaborators found that the impact of the messages on the signs depended critically on how they were phrased. When the messages were written in the form of injunctive norms--as in, "Please don't remove the petrified wood from the park"--they reduced theft significantly. But when they were written in the form of descriptive norms--as in, "Past visitors have removed the petrified wood from the park, changing the state of the Petrified Forest"--they had almost no impact.

Cialdini surmises that descriptive norms, especially those that describe a prohibited activity as "regrettably frequent," give people the impression that violating the prohibition is something everyone does. Injunctive norms, in contrast, alert people to the social unacceptability of the behavior.

The ideal message, says Cialdini, would combine an injunctive norm with the right kind of descriptive norm--one that stresses the extremely small number of people who actually violate the injunctive norm, and the disproportionately large amount of harm they cause.