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The environment — and especially the subject of climate change — is one of the most polarizing topics in American politics. This fact is obvious and indisputable — but what is the root reason behind it?

Psychologists are beginning to probe that question using the tools of their trade — surveys, questionnaires and correlations. For instance, a study that we reported on here in January found that the personality trait “Openness to Experience” — wanting to try out new things and new experiences in life — was linked to green tendencies. And now, another paper has found another emotional and personality-based driver of environmental attitudes: namely, a heightened sensitivity to the suffering of other people.

The study, published recently in the journal Environment and Behavior, is by Stefan Pfattheicher of Ulm University in Germany and two colleagues. With a sample of over 2,000 individuals, including college students, along with citizens of the Netherlands, the researchers asked about people’s environmental behaviors and values but also a series of questions designed to measure “emotional empathy.” One example: an item in which individuals are asked how much they agree with the following statement: “It makes me sad to see a lonely stranger in a group.”

[Read: Can your personality explain how you feel about the Keystone XL pipeline?]

It may not seem immediately apparent why empathy for other humans translates into concern for the environment, where issues (like air pollution) often affect humans but other times focus on animals, plants or nature itself. Empathy for a tree and empathy for a person do not initially seem as though they would be the same thing.

Nonetheless, the study found a small- to moderate-sized correlation between this measure of empathy and environmental values — as well as environmental activities. For instance, reported the authors, “the stronger a participant’s dispositional compassion the higher the chance that they would donate to one or more nature or environmental organizations.”

The study didn’t stop there. It also tried to test the “causal relationship” between empathy and environmentalism. How do you do that? You need an experiment in which people are made to feel more or less compassionate, and then subsequently studied to determine how that experience affects their environmentalism.


The Lorax demands to know who chopped down the Truffula Tree in “Dr. Seuss’ The Lorax.” (© 2012 Universal Pictures and Illumination Entertainment)

In this case, the researchers used a smaller sample — 94 German university students — all of whom were shown two pictures of human suffering: “a homeless person leaning against the wall of a house and a diseased child.” Half the sample was told to feel empathy toward those depicted in the images, while the other half was instructed to “try to stay neutral and detached.”

Then the participants’ “environmental intentions” were measured — for instance, how much they agreed with statements like, “In future, I will look for ways to reuse things.” The result showed that those who had been instructed to feel compassion showed stronger environmental intentions as well.

The authors conclude that “compassion elicits moral judgments and actions across different moral domains” — in effect, that it’s infectious.

The research is consistent with other studies that use a “moral foundations” framework to examine what drives people in politics, a paradigm that has detected numerous moral and emotional differences between liberals and conservatives. In moral foundations studies, people are asked about what kinds of considerations count in determining what is right and wrong, and provided with items like “whether or not someone suffered emotionally” and “whether or not someone’s action showed love for his or her country.”

Liberals tend to more heavily emphasize the emotional suffering item above (which researchers dub the “care/harm” moral foundation), while conservatives more favor concerns about loyalty and following authority. And sure enough, moral foundations researcher Ravi Iyer found in 2013 that sensitivity to considerations about care and harm were also associated with a desire to “protect the environment” in a large sample of over 15,000 people who had taken the “moral foundations” questionnaire online.

It is important to note that members of the two political groups are sensitive to all of the moral foundations — it’s just that they may feel some more strongly than others. Thus, the research should not be misunderstood as suggesting that conservatives don’t care about compassion or that liberals don’t care about loyalty. It’s just that they have different moral complexions, which blend the ingredients of morality together differently.

The new research is valuable in that it helps us better understand why different people respond differently to the environment — but from a conservative perspective, it may also reinforce a stereotype about “tree hugging.” Moreover, it may feed into a critique of environmentalism for being too rooted in emotion, rather than hard cost calculations and an awareness of the necessity of making difficult trade-offs.

So, we’ll most assuredly remain divided over environmental issues like the Keystone XL pipeline and protecting endangered species — but just maybe, we’ll have a little bit more awareness about why.