Comprehensive sex education works. Years of research show that it is much more effective than an abstinence-only approach at preventing teen pregnancy. In fact, abstinence-only programs may actually increase unplanned pregnancies and can contribute to harmful shaming and sexist attitudes.

Yet abstinence, or “sexual risk avoidance,” programs persist in the U.S. Why? Ultimately many people believe that teenagers should not have sex. If adolescents just abstain, they reason, unplanned pregnancies and sexually transmitted diseases will no longer be a problem. By contrast, comprehensive sex education operates under the premise that some young people do engage in sexual behavior, so it is worthwhile to help them understand how to avoid unwanted outcomes. For dedicated abstinence-only advocates, however, that approach is morally wrong.

Given the deeply held moral beliefs many people bring to this topic, it’s easy to think the debate over sex ed is doomed to a stalemate between those who want to ban it and those who want to promote it. And this is just one of several subjects where policy makers face a tough choice: ban or prohibit a potentially harmful activity, or allow it to continue while mitigating the harm. Mitigation options include needle-exchange programs that help people who use intravenous drugs lower their risk of contracting blood-borne illnesses. Another example is mandatory waiting periods for firearms purchases, which allow people to possess firearms but also reduce homicides.

These harm-reduction strategies are often effective, but they can be unpopular. That’s because issues like sexual behavior, drug use and gun ownership involve highly moralized opinions. Research shows that when people feel moral outrage toward a behavior, they are more likely to support policies that aim to completely stop that activity rather than make it safer.

But our research suggests that not all expressions of moral outrage are alike. Through a series of studies that involved surveying more than 1,000 Americans, we found that, in some cases, people base their moral opposition on the harm that an action causes. In those instances, if you can find ways to make an activity safer, you can also make it more morally acceptable.

In our first two studies, we asked people about topics that we knew many strongly oppose: smoking, risky sexual behavior and gun ownership. Importantly, all of these topics can trigger moral objection, but these perspectives do not cluster with a particular political ideology. We first asked participants about policies that would reduce the harm of each behavior and then asked them for their moral judgments of those same behaviors.

We received a wide range of responses. We found people who completely supported each of these behaviors, as well as people who objected strongly. Generally speaking, the more people morally opposed something, the less they supported an associated harm-reduction policy. For example, the more strongly people were against engaging in risky sexual behavior, the less supportive they were of initiatives to provide medicine that protects against HIV.

But we wanted to dig deeper. Researchers who study moral psychology have found that moral judgments often relate to harm. In other words, we may judge something as morally wrong because it’s harmful. So we wanted to know why policies that reduce harm are unpopular among people with strong moral reactions—wouldn’t reducing harm be a good thing?

In a third study, we assessed a new group of people and again asked whether they would support a harm-reduction strategy related to these three provocative issues. Then we again asked how strongly they opposed each behavior. We also asked the participants to rate how harmful, threatening or dangerous they believed certain issues were—and how much suffering the activity might cause.

This time we were surprised. We found that for gun ownership and risky sexual behavior, the more harmful people thought the behavior was, the more they supported a harm-reducing policy. In other words, our data presented a paradox: wrongfulness and harmfulness usually go together, but we found that perceiving something as wrong was linked with opposing a harm-reduction policy, whereas perceiving something as harmful was tied to supporting such a policy.

To explore this relationship between harmfulness and wrongness further, we designed a fourth study that included hypothetical questions such as “If there was no harm associated risky sex, would it be wrong?” and “If there was no harm associated with gun ownership, would it be wrong?” The results revealed that two distinct kinds of moral response exist. Some people showed strong moral opposition to the activity, even if it was harmless. For them, the issue was black-and-white: this behavior is wrong. The more strongly they felt the behavior was morally wrong, the less they supported harm-reduction policies.

Other people, however, had a moral response rooted in how harmful the activity may be. For these people, the behavior was wrong but could become perfectly acceptable if it were somehow harm-free. They could support for a harm-reduction policy despite their moral objections to the activity.

Our work suggests that not all moral judgments are alike. If we want to understand one another or persuade others to consider ways of reducing harm, we need to pay attention to what motivates people’s moral judgments. That insight is valuable to policy makers who want to implement harm-reduction strategies. It also holds promise for those who may fear certain conversations are too morally charged to be productive or even pleasant. Our findings show that someone can have a strong moral objection to a behavior and yet be willing to entertain strategies that allow for some form of the activity to continue. In other words, just because people harbor moral opposition to a behavior does not necessarily mean their thinking is rigid or uncompromising when it comes to policy.

Lastly, our work hints at a starting place for discussing these morally sensitive topics. When we asked some of the people in our studies whether they felt for those involved in the potentially harmful behaviors we had presented, we found that people who expressed some compassion also showed greater support for harm-reduction policies. Perhaps, if we can start by considering those who suffer, there could be a new path forward for policies that improve and save lives.

Are you a scientist who specializes in neuroscience, cognitive science or psychology? And have you read a recent peer-reviewed paper that you would like to write about for Mind Matters? Please send suggestions to Scientific American’s Mind Matters editor Daisy Yuhas at