On any given day, how much meat does the average vegetarian eat? Since vegetarians, by definition, don’t eat meat, this question should be boring because of course the answer is zero. This question isn’t boring at all, though, because it has a very specific, very not-zero answer—83.2 grams, about one standard serving.

With this in mind, it’s not so surprising that a recent survey shows that one third of vegetarians eat meat while they’re drunk.

This first figure—seriously, the average vegetarian in the U.S. eats one serving of meat per day!—comes from a 2003 analysis of data collected by the U.S. Department of Agriculture in the late 90’s. The researchers examined responses from a representative sample of nearly 10,000 Americans who had detailed everything they ate over two separate and nonconsecutive 24-hour periods. And vegetarians, it turns out, eat meat. About 40 percent of what the typical American reported—220 grams or so—but meat all the same.

This doesn’t necessarily mean that every vegetarian eats meat, since this figure is only an average, but most vegetarians in the U.S. do. Another survey from the USDA, also conducted by phone, put the number of vegetarians who’ve eaten meat in the last day at about two-thirds. Based on a 1995 survey of wealthy, well-educated Americans from the East Coast, only 1.5 percent said they never eat poultry or fish, but 7 percent called themselves vegetarians. Surveys by Canada’s National Institute of Nutrition put the number of Canadian vegetarians who eat chicken at about 60 percent and red meat at about 32 percent.

The survey suggesting that vegetarians eat meat while they’re drunk is a bit less rigorous—it’s based on a survey conducted by a U.K.-based coupon company, VoucherCodesPro, who hasn’t publicly released any methods or details about the subjects involved—but it’s plausible. I did exchange emails with a member of the PR firm that represents VoucherCodesPro, but they preferred not to be named and gave me a rough description of the methodology. In any case, these results should be taken with some healthy skepticism.

If anything, it’s suspicious that so few vegetarians cop to eating meat while wasted, since twice as many admit to eating meat on any given day. So whether or not this survey is accurate, it still raises interesting questions.

To help understand what’s going on, I spoke with Hank Rothgerber, a social psychologist at Bellarmine University whose research has touched on vegetarians and how they’re viewed. Rothgerber suggested that much of what’s happening might involve the reasons people are vegetarians to begin with.

“Probably a greater percent of those who have fallen off the wagon are health vegetarians,” Rothgerber suggested. “Ethical vegetarians tend to have more reasons for why they’re avoiding meat and why they don’t eat meat in the first place and probably have a stronger commitment to it.”

“If you’re a health vegetarian,” Rothgerber went on, “it’s just a matter of self-control or self-regulation. It would be the same as anyone who is trying to eat a healthy diet.” In this sense, it’s hardly surprising that vegetarians who avoid meat for health reasons stray sometimes—no more surprising, at least, than hearing that most people on a diet sometimes eat cake, especially while drunk.

Some research on lapsed vegetarians supports this. Faunalytics (formerly the Humane Research Council) conducted a survey on 11,000 American adults, which found that there are five times as many ex-vegans and vegetarians as there are current ones. About 60 percent of them said that the reason they were vegetarian in the first place was for the health benefits. In this frame, lapsed vegetarians are no more extraordinary than lapsed dieters.

But there are people who are vegetarians and vegans for ethical reasons and who still occasionally eat meat. (Full disclosure: I’m a vegan for ethical reasons and very rarely eat meat, almost exclusively while drunk). Here, so long as you exclude those who sometimes eat things like oysters since they have no nervous systems and can be farmed sustainably and are basically for all intents and purposes meat plants (thus most of my sober meat consumption), the reason for lapsing seems equally mundane: some vegetarians like the taste of meat, and we sometimes do things we want to do even when we know we shouldn’t.

Here, one of Rothgerber’s studies makes the difference between strict vegetarians and those who sometimes stray even clearer: he found that those who never cheat on their diets were more disgusted by meat, and found meat less appetizing, than those who sometimes cheated. It turns out it’s easier not to eat meat if you don’t want to.

“I think part of the problem that vegetarians face is the fact that we live in a meat eating world, at least Western societies are meat eating societies, so there’s not a lot of social support,” Rothgerber told me. “I think to some degree vegetarians who find themselves situated in other groups and social networks with like minded folks are much more likely to continue with the diet,” he went on. “I think that’s part of what makes it difficult, it’s very much the social aspect. I would guess that’s a much bigger factor than ‘I miss meat too much’ or ‘I just found it too difficult.’

Faunalytic’s survey on ex-vegetarians supports this broader point. When they explained why they stopped being vegetarian, few people said they changed their minds about animal ethics. Instead they cited more mundane reasons—almost two-thirds said they didn’t like sticking out, about half said they found it too hard to keep such a “pure” diet, and about a third noted that their significant others ate meat.

It’s these other factors, less the moral ones, that seem to matter most when it comes to getting people to follow through on their vegetarian diets. Eric Schwitzgebel, a philosopher who often studies the views of other philosophers, has helped demonstrate how sometimes the ethical argument isn’t the most important path to different eating habits: moral philosophers are more likely than other philosophers to say that eating meat is wrong, but no more likely to actually eat less meat.

In his 2006 book The Happiness Hypothesis, the social psychologist Jonathan Haidt described two experiences he had in graduate school which also demonstrate some of the limits of our moral beliefs. First, he describes how a book written by the moral philosopher Peter Singer affected him.

“Singer’s clear and compelling arguments convinced me on the spot, and since that day I have been morally opposed to all forms of factory farming. Morally opposed, but not behaviorally opposed,” Haidt wrote. “I love the taste of meat, and the only thing that changed in the first six months after reading Singer is that I thought about my hypocrisy each time I ordered a hamburger.”

A year later, however, Haidt described a very different experience. As part of a study exploring the psychology of disgust, Haidt watched a video of cows going through a slaughterhouse. “I watched in horror as cows, moving down a dripping disassembly line, were bludgeoned, hooked, and sliced up,” Haidt wrote.

“For days afterward, the sight of red meat made me queasy. My visceral feelings now matched the beliefs Singer had given me,” Haidt went on. “I became a vegetarian. For about three weeks.”

Vegetarian advocates seem to have had better success at convincing people that it’s a good thing to eat less meat—it really is much better for the environment, better for our health, and better for animals—but a comparably much poorer job of helping people follow through. Of those who were once vegetarians, a sizeable portion, 40 percent, admit that they’re interested in returning to a plant-based diet. This would effectively double the number of existing vegetarians in the United States, but require a more sophisticated appreciation of the difference between moral opposition and behavioral opposition.

“If I was running some advocacy groups, I’d try to promote vegetarian clubs or groups or eating organizations that would encourage some sort of way of putting vegetarians in greater contact with one another,” Rothgerber told me. “Host dinner parties, have eating clubs, basically I would be trying to link as many vegetarians with each other as possible. The more vegetarians are isolated and by themselves in this behavior, then the worse things will be.”