If a cow could eat you, it would. It wouldn’t give a hoot about your feelings. It wouldn’t kill you quickly or humanely and it certainly wouldn’t worry about whether it was right to make a meal of you in the first place. It would ask itself one question: Am I hungry? If the answer was yes, you’d be lunch.

In that one way, at least, the carnivorous cow would be smarter than we are. The hard truth is, we eat meat, we love meat, and our bodies are built to digest meat. It would be nice if we could pick the stuff off the trees, but we can’t. So apologies to goats and pigs and cows and chickens and fish and lobster and shrimp and all the other scrumptious stuff that flies and walks and swims, but you’re goin’ down.

That, of course, is the primal, flesh-craving part of our brain talking. But other parts—our softer, cuddlier, morally tormented parts—are consumed by guilt over taking a life to make a meal. The only way to reconcile our minds, to say nothing of our menus, is either to go vegan—try that for a week—or to convince ourselves that despite the critter murder we effectively endorse every time we tuck into a pork chop or a chicken salad, we are still somehow decent, somehow good. That takes some fancy ethical footwork.

The main dodge we usually rely on is the “animals can’t think so they never know what hit them” excuse. That may well be true when you get below a certain point on the cognitive scale. As no less a figure than Princeton bioethicist Peter Singer—whose 1975 book Animal Liberation launched the animal rights movement—told me in an interview a few years ago: “I think there’s very little likelihood that oysters, mussels and clams have any consciousness, so it’s defensible to eat them.”

That case gets harder to make as you climb the critter ladder, and even chickens—as sublimely dumb a bird as ever lived—must have at least a dim light flickering upstairs, never mind pigs or even octopi that exhibit complex behaviors and a certain cleverness. But as a new study published in Current Directions in Psychological Science shows, we’ve found ways around that problem too.

In a series of experiments and surveys, a team led by research psychologist Steve Loughnan of the University of Melbourne confirmed that while people across a broad range of cultures agree that the more mindful an animal is, the less defensible it is to eat it, we have a convenient way of deciding which critters think and which don’t. If you like beef, you’re more inclined to believe cows can’t think; if you eat only fish, you’re likelier to see cattle as conscious, while the salmon on your plate was probably a non-conscious nincompoop.

That handy reasoning even works in an ex post facto way. Loughnan found that a subject who had just eaten beef and was then asked about cow consciousness tended to rate it low, while someone who had just eaten nuts gave cows more credit. We justify food even after we’ve already consumed it. We do something similar with any animal that either through charisma or companionability has achieved a sort of most favored fauna status. So a hamburger is fine, but a horseburger? We’re not barbarians. Ditto shark fin versus dolphin fin soup, and turkey versus, say, eagle for Thanksgiving.

None of this ethical expedience is necessarily a bad thing; indeed it’s a necessary skill for a species with a conscience like ours trying to make its way in a morally ambiguous world. But we shouldn’t pretend it’s more than expedience. The vegetarian’s truth is no more legitimate than the pescetarian’s or the red-in-fang carnivore’s. We can all agree that gratuitously subjecting animals to suffering is a bad thing, and it’s the rare human who could look at unnaturally fat chickens or pigs in cages or crates that barely allow them to move without thinking that we’ve gone terribly wrong somewhere. Still, in most cases, we make our own peace in our own way with what’s on our own plates. Pay your own check and the meal is up to you.

Write to Jeffrey Kluger at jeffrey.kluger@time.com.