Obviously, such DNA labels would be absurd. Nearly all food contains DNA, and there is no good reason to warn consumers about its presence. As McFadden and Lusk and explain, the survey answers on this subject are an indication of widespread scientific ignorance, proving that many of the respondents “have little knowledge of basic genetics.” Other data from the study also support this conclusion, including the fact that 33 percent of respondents believe that non-GMO tomatoes do not contain any genes, and 32 percent think that vegetables have no DNA. Our vegetables would be blissfully free of DNA if not for the nefarious corporations who maliciously insert it into the food supply!

The authors note that the proportion of respondents who support labeling of foods containing DNA is very similar to the percentage who support mandatory labeling of GMO foods (84 percent). They suggest that some respondents may support labeling because they are using crude, but understandable, heuristics:

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Rather than seriously weighing the pros and cons of a mandatory labeling, the similarity in responses to the DNA labeling question suggests people may instead be substituting these questions with a simpler question like, ‘do you want free information about a topic for which you know very little?’ This psychological process would lead to similar levels of support to two very different policy questions.”

This may be true. But it is not very reassuring. The question of DNA labeling is not a hard one for anyone who actually knows what DNA is (the basic genetic building block of all life on earth). Moreover, mandatory provision of “free” information is not really free at all. Labels cost money. Those costs will often be passed down to consumers. They also take up the time of consumers, and potentially divert their attention away from more valuable information. Mandatory labeling of substances that are not actually risky can also mislead people into thinking that a threat exists even where it does not. Government-mandated warnings are themselves often risky. Perhaps we even need to adopt a warning against government warnings:

WARNING: Following government-mandated warnings like this one will sometimes be hazardous to your health, your happiness, or your pocketbook. The government is not liable for any injury or financial losses you may incur by adhering to this warning. Exercise caution and proceed at your own risk.

Obviously, the government is not likely to adopt mandatory labeling of DNA anytime soon. But, as McFadden and Lusk, the mandatory labeling of GMO foods is also a dubious policy of this type, given that the overwhelming majority of scientists believe that genetically modified foods are not inherently more dangerous than those that are not.

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The new study does have one relatively hopeful finding. While most of the public is ignorant about the scientific issues involved in food labeling policy, many may realize that such public ignorance is a problem. Some 65 percent of respondents indicated that decisions about the labeling of GMO foods should be made based on “the views and advice of experts,” as compared to only 35% who thought that they should be made based on the views of “average Americans.” Deferring to the views of experts on complex scientific questions like these is indeed a wise strategy in many situations. But it may not be an adequate substitute for knowledge of basic scientific and political facts. People who are ignorant about such matters may also find it difficult to figure which people really are expert enough to justify deferring to their judgment. In most public policy controversies, both sides can trot out at least a few seeming experts who will endorse their positions. Separating out serious experts from quacks may be a very difficult task for ignorant voters. Ditto for the task of telling the difference between a question on which there is a genuine expert consensus, and one where there is not. The near-consensus among experts that GMO foods pose no special risk has not prevented the vast majority of the public from continuing to believe otherwise.

Sadly, there is no easy solution to widespread scientific and political ignorance. In my work on the subject, I have argued that the most promising approach is to limit and decentralize the power of government, which would enable us to make more of our decisions in settings where we have stronger incentives to become well-informed. At the very least, we should recognize that we have a serious problem with voter ignorance, and that majority public opinion is often a very poor guide to policy.

But if we do decide to follow majority opinion on these issues, and adopt labeling of foods containing DNA, I renew my suggestion of the following language for the mandatory warning:

WARNING: This product contains deoxyribonucleic acid (DNA). The Surgeon General has determined that DNA is linked to a variety of diseases in both animals and humans. In some configurations, it is a risk factor for cancer and heart disease. Pregnant women are at very high risk of passing on DNA to their children.