It’s difficult to determine when discussions of controversial topics became known as hate speech on college campuses across the country. But the metamorphosis has taken place all around us, and the costs are undeniable. Open debate has morphed into self-censorship and terrified silence; what used to be celebrated as an environment of fearless questioning has become a stultifying world of repression.

Intolerance of meaningful debate comes from both sides of the political spectrum. Talk of “black lives matter” constitutes hate speech for some, while “blue lives matter” fits the bill for others. Depending on the political leanings of their particular campus, professors, staff members and students are strongly discouraged from entertaining certain topics even privately, much less discussing them publicly on campus, because these discussions make some people uncomfortable. The risks and penalties are tangible and significant, from shaming and ostracizing, to fear of loss of tenure and jobs for professors and expulsion and dismissal for anyone else.

What specific topics are off-limits on college campuses today? Consider recent examples from a Cato Institute survey of over 3,000 Americans with university experience: 40 percent would ban a speaker who says men on average are better than women at math, 51 percent would ban claims that all white people are racists, 49 percent would ban statements that Christians are backward and brainwashed, 49 percent would ban speech that criticized and disrespected police, and 41 percent would ban speakers who say undocumented immigrants should be deported.

Our concerns over these figures is not because we agree or disagree with the statements. But shouldn’t college students be exposed to arguments on both sides of these issues, as part of their journey of intellectual development?

The Cato survey reported a willingness to censor, regulate or punish a wide variety of expression people found offensive: 74 percent of respondents said universities should cancel speakers if students threaten violence, and 51 percent of those who self-identified as strongly liberal said it is “morally acceptable to punch Nazis in the face.”

When older adults think about their college experience, they remember heated debates with eye-opening proclamations that deliberately challenged preconceptions and created real discomfort along the way. An essential aspect of college was broadening students’ thinking in ways they could never have predicted. In the 1960s and ’70s, conservative administrators were taken to task for muzzling students’ free expression. Ironically, there is currently a lot of talk about free speech on college campuses, but the vast majority focuses on how to regulate it.

Meaningful debate on uncomfortable important topics is replaced by proclamations based on “lived experiences” and “emotional knowledge.” But it is impossible to refute a person’s claim of a lived experience that caused her suffering. If this rubric is how we define permissible speech, very soon nothing worthwhile qualifies. The heckler’s veto reigns supreme.

Today’s college students respond to statements that make them uncomfortable with allegations of speakers’ criminal intent. Dartmouth College students railed against an op-ed published in the school’s newspaper by undergraduate Ryan Spector (here) after he criticized the process that resulted in four men and 15 women being chosen as mentors. Spector argued this disparity was the result of a selection process “that sees race, gender and identity as dictating qualification.” More than 30 campus organizations denounced Spector, calling his piece an “attack” on women and minorities, claiming it “endangers the lives” of students, and suggesting Spector be punished for his views. Others lamented “how violent this article is,” urging the paper to retract it and require Spector to apologize and stating that allowing Spector and others like him to express their opinions endangers “the safety and well-being of marginalized students” and “only further perpetuates the culture of toxic, male, white supremacy.”

We considered these issues in a new article in Perspectives on Psychological Science on the controversies surrounding recent cancellations of campus talks. We drew mainly on psychological, legal and philosophical analyses to explain the polarization of positions, focusing on phenomena known as blind-spot bias, selective perception, motivated skepticism, my-side bias, groupthink and naïve realism, which help explain why dueling sides overestimate support for their own position and downgrade opponents’ views. In the campus disturbances, opponents did not simply interpret the same situation differently, they actually saw different things.

A number of recent campus disruptions share one or more of these biases: opponents offered different accounts about who started the violence, the role campus police played, why each side’s affiliation with a cause led to the belief that it was especially enlightened whereas opponents’ opposite affiliation led to their own flawed reasoning, why people on each side overestimated the strength of the evidence supporting their side, and whether protesters shouting down of speakers infringed on the audience’s right to hear their views or, conversely, represented exercises in their own freedom of expression. We concluded our article with recommendations to moderate positions and inculcate a campus culture of respectful debate in which no single group appoints itself the final arbiter of what can and cannot be heard.

Having one’s beliefs criticized -- even identity-forming beliefs -- is an essential aspect of a good education. College is an opportunity to confront divergent opinions, even if they make us uncomfortable; being exposed to opinions that call into question their deepest beliefs will help students develop the valuable skills needed to navigate their futures, relate to others with divergent views and contribute to society. As uncomfortable as it might be, there really is no viable alternative to allowing free speech on college campuses.

How can our colleges and universities create an open atmosphere of free speech while also respecting diversity?

First, give all sides a podium for expression. No campus group has the right to determine for the entire community what can be discussed. But protesters also have a right to be heard. Make viewpoint diversity an important component of diversity, broadly defined; ensure panels, committees and faculty and staff all contain individuals with views occupying the entire political spectrum. Psychological research shows that we all possess and must acknowledge our biases, and humility will go a long way toward accomplishing this goal. The best and most effective airing of controversy takes place within the marketplace of ideas.

Second, college experiences should involve challenges to our beliefs even when those experiences go beyond our comfort level. Colleges might begin by inculcating a culture on campus in which students are expected to become informed about controversial speakers’ views, either by listening to their arguments or by reading their positions. Role-playing exercises, in which supporters of each side are asked to switch sides, can also be valuable.

Third, similar role-playing exercises could be woven into controversial seminars in the social sciences and humanities and even in some natural sciences (e.g., on the role of humans in climate change, safety of GMOs, theory of evolution/origin of the universe, ethics of fetal stem-cell therapies, drilling in the Arctic Refuge, and CRISPR gene editing). Researching multiple sides of a contentious argument can help prevent ideological groupthink. It can even engender empathy for others and help routinize attempts to falsify one’s pet theory and supplement it with efforts to disconfirm personal bias.

Fourth, during freshman orientation at our university, students are informed about codes of conduct related to plagiarism, intoxication, sexual harassment and so forth. They must pass online tests based on curricula (e.g., alcohol.edu). These are important issues, and entering students must demonstrate that they have read and understood these codes. However, freshmen are not encouraged to think about issues related to free expression, hate speech, what constitutes “evidence” or what is and is not protected expression by campus speech codes -- as well as by the U.S. Constitution. They should be.

The take-home message from college should not be that feeling uncomfortable at hearing a collection of words strung together is grounds for censoring those words. A better lesson would be to learn to endure discomfort, to listen openly to alternative sides, and to respond with reasoned and effective counterarguments (when appropriate). College students should learn that reasonable, decent people will surely disagree with them about the ideas they hold most dear. This does not mean others are correct; they may be misguided and wrong, but the answer is not censorship.

As the philosopher John Stuart Mill noted, when we assert that a topic is too controversial to be debated, we foreclose all argument, thinking and reasoning that might ultimately derive from the unfolding debate. Considering the list of “off-limits” topics on college campuses today, we must ask if we truly want college life to deprive young minds of the opportunity to develop that would be afforded by meaningful debate on these key issues of our time.