As of right now, there are few issues which so neatly divide the country in half as the legalization of marijuana. A new study out this year shows that support for the legalization of pot is creeping up toward 50%, up from a mere 16% a little over ten years ago.
Why? Why are we as a nation so divided on this issue? Roughly half of us seem to think that Washington shouldn't be meddling with exactly which plants we crush into our the bowls of our bongs. The other half seems to think that it's fine for people to spend their leisure time drunk - no one wants a return to prohibition - but it's not ok for people to spend their leisure time stoned. Why?
The obvious answer is that it's all about politics. Blue people's politics are socially liberal, and this is what's driving their views on drugs. Red people are socially conservative, and so they oppose drugs.
This explanation is obvious and appealing, and it's only drawback is that it doesn't seem to be terribly consistent with all the data. Suppose that differences in people's political views were responsible for the differences in views on drugs. In this case, if we simply ask people their political views - liberal versus conservative - and whether or not they oppose drugs, we ought to find a satisfyingly strong relationship. (See the postscript for a remark on correlation and causation.)
Two collaborators (Amber Dukes and Jason Weeden) and I asked about a thousand people to answer a battery of questions, including how morally opposed they were to recreational drugs along with a bunch of other questions, including an assessment of their political views. This allowed us to measure how well political views predicted drug views.
There is a relationship, but it's relatively small. If I know that you're conservative or liberal, I can do a bit better than chance at predicting your views on recreational drugs.
Not only that, but there are a whole bunch of other questions that did a better job at predicting people's views on whether or not recreational drugs should be illegal. Before I tell you what questions those are, what do you think the answer is? Suppose that you just met someone, and I would pay you one dollar if you could accurately predict their views on drugs. You can ask them one question, with the obvious exception of their views on drugs (and related, leading questions, of course). What would you ask them?
If they answer yes, it is OK, then you can predict with a certain degree of accuracy that they will be in favor of legalizing pot. If they answer no, then, obviously the reverse.
We asked a whole battery of survey questions, and out of all of the items we asked, this question was the best predictor of people's stated views on the morality and legality of recreational drugs.
We did not, I should say, ask people just any old questions. We used questions that different theories say should relate to views on drugs. And, of course, we used questions that our own theory predicted should be related to views on drugs.
So, there's the question. Why should the same people who think sex without love is OK be the ones who also favor the legalization of marijuana? Or, put the other way, why do people who think sex without love isn't OK oppose recreational drug use?
Remember in your answer to this question, you can't go back to the Color Theory of Morality, that it's political views that are causing both: you can't guess someone's views on drugs from their political views as well as you can from the question about sex.
So, is could opposition to drugs really be all about sex? And if so, why?
(Postscript: There is a mantra among psychologists that correlation does not imply causation. That is, if you see two things are related to each other, that doesn't mean you can logically infer that one caused the other. I see people with umbrellas when it's raining; I can't infer from observing that relationship that umbrellas cause rain. However, if I make a claim that one thing causes another, then, generally, I have to predict that they will correlate with one another. If I claim that rain causes people to open umbrellas, but I look to see and find that there is no relationship between rain and open umbrellas, I've probably got the wrong causal account. For this reason, looking at correlations is useful for falsifying causal claims. For an amusing take on this, see http://xkcd.com/552/)
Copyright Robert Kurzban 2011. All rights reserved.