The findings were striking. When participants were in diverse company, their answers were 58 percent more accurate. The prices they chose were much closer to the true values of the stocks. As they spent time interacting in diverse groups, their performance improved.

In homogeneous groups, whether in the United States or in Asia, the opposite happened. When surrounded by others of the same ethnicity or race, participants were more likely to copy others, in the wrong direction. Mistakes spread as participants seemingly put undue trust in others’ answers, mindlessly imitating them. In the diverse groups, across ethnicities and locales, participants were more likely to distinguish between wrong and accurate answers. Diversity brought cognitive friction that enhanced deliberation.

For our study, we intentionally chose a situation that required analytical thinking, seemingly unaffected by ethnicity or race. We wanted to understand whether the benefits of diversity stem, as the common thinking has it, from some special perspectives or skills of minorities.

What we actually found is that these benefits can arise merely from the very presence of minorities. In the initial responses, which were made before participants interacted, there were no statistically significant differences between participants in the homogeneous or diverse groups. Minority members did not bring some special knowledge.

The differences emerged only when participants began interacting with one another. When surrounded by people “like ourselves,” we are easily influenced, more likely to fall for wrong ideas. Diversity prompts better, critical thinking. It contributes to error detection. It keeps us from drifting toward miscalculation.

Our findings suggest that racial and ethnic diversity matter for learning, the core purpose of a university. Increasing diversity is not only a way to let the historically disadvantaged into college, but also to promote sharper thinking for everyone.

When it comes to diversity in the lecture halls themselves, universities can do much better. A commendable internal study by the University of Texas at Austin showed zero or just one African-American student in 90 percent of its typical undergraduate classrooms. Imagine how much students might be getting wrong, how much they are conforming to comfortable ideas and ultimately how much they could be underperforming because of this.

Ethnic diversity is like fresh air: It benefits everybody who experiences it. By disrupting conformity it produces a public good. To step back from the goal of diverse classrooms would deprive all students, regardless of their racial or ethnic background, of the opportunity to benefit from the improved cognitive performance that diversity promotes.