Philosophers and ethicists have never had scientific proof that university ethics classes affect student moral behavior — until now.

A research team led by a philosopher at the University of California, Riverside, has conducted the first controlled study aiming to discover whether such a correlation exists using direct observational data rather than self-reported information.

The study found that after exposure to a philosophy article, a 50-minute discussion section, and an optional online video concerning the ethics of eating factory-farmed meat, students decreased their rates of meat purchasing from 52% to 45%. That compared to a constant rate of 52% among students in a control group exposed to similar materials on the ethics of charitable giving. The study, conducted at UC Riverside, included 1,332 student participants. Food purchase data was gathered from the students’ campus dining receipts, with identifying information stripped away for privacy, and included only purchases of $4.99 or more.

Additionally, questionnaires distributed to the students revealed a substantial change in moral opinion about the ethics of eating factory-farmed meat following the study. Among the students studying the ethics of charitable giving, 29% of participants agreed “eating the meat of factory-farmed animals is unethical” compared to 43% of the students who studied the ethics of eating meat.

Eric Schwitzgebel, a professor of philosophy at UC Riverside and lead author of the paper, said the researchers chose to focus on the ethics of eating factory-farmed meat for three reasons. First, opinion on the topic among the general public is highly variable and people are likely to change their minds compared to other topics. Second, there is widespread philosophical consensus that, in general, it is morally better for the average North American to consume less factory-farmed meat. Lastly, meat consumption is directly measurable.

He added the goal of the study was not specifically to convince students to eat less meat, but to find out whether philosophical ethical instruction is even capable of influencing real-world choices.

“Part of the framework for thinking about the humanistic mission of a university is to think about whether classes of this sort actually do affect students’ behavior,” Schwitzgebel said. “There is some evidence that teaching ethics typically doesn’t have much impact on people’s real-world choices. If that were the case universally across the board, then teachers might have different types of aims and expectations than if there is evidence the way we teach things does influence student behavior.”

The paper, “Do ethics classes influence student behavior? Case study: Teaching the ethics of eating meat,” was published this month in the journal Cognition. Co-authors include Bradford Cokelet of the University of Kansas and Peter Singer of Princeton University. The project was financed by a grant from Princeton's University Center for Human Values and an Academic Senate grant from UC Riverside.

In follow-up research, the philosophers hope to better explore the effect of different teaching styles on opinion and behavioral changes in students, and more carefully examine the possible effects of watching or not watching the film.

The required reading for the class was James Rachels’ 2004 article, “The Basic Argument for Vegetarianism.” The optional video was an 11-minute vegetarianism advocacy film called “What Came Before,” which was released in 2012.  

Schwitzgebel said learning more about what specifically led to behavioral changes could help further understanding of effective advocacy techniques.

“If it turns out that what was effective is something transportable outside of the classroom, say reading the paper and viewing the video and not the dialogue with the teaching assistant, then people who are advocating for vegetarian causes could then disseminate the video and paper and hope for a positive effect,” he said. “To the extent it helps illuminate the general relationship between philosophical reasoning and real-world choice, the more we can think about that relationship in our daily practice.”