It's called the meat paradox: the fact that we can snuggle up to some animals – and stick others on the end of our fork.

How do we manage to tread this line, lamenting horses that died in WWI on one hand but eating cows on the other, or reading stories about Piglet and Babe to our kids and then feeding them ham sandwiches?

How do we lament horses that died in WWI but not feel sad about killing cows? Credit:Belinda Pratten

Some clues come from new research into how we justify eating meat led by the UK's University of Lancaster and published in the journal Appetite. Asked why they ate meat, most people gave four main reasons which the researchers called the Four 'N's: that meat eating is Natural ("humans are natural carnivores"), Necessary ("meat provides essential nutrients"), Normal ("I was raised eating meat") and Nice ("it's delicious"). Of all these reasons "necessary" was the most common.

The people who endorsed the Four Ns were more likely to be men. They also felt that cows were less likely to experience feelings like sadness and joy, says one of the researchers, Mirra Seigerman of the University of Melbourne's School of Psychological Sciences.