But one by one, the berms we’ve built between ourselves and the beasts are being washed away. Humans are the only animals that use tools, we used to say. But what about the birds and apes that we now know do as well? Humans are the only ones who are empathic and generous, then. But what about the monkeys that practice charity and the elephants that mourn their dead? Humans are the only ones who experience joy and a knowledge of the future. But what about the U.K. study just last month showing that pigs raised in comfortable environments exhibit optimism, moving expectantly toward a new sound instead of retreating warily from it? And as for humans as the only beasts with language? …

All of that is forcing us to look at animals in a new way. With his 1975 book Animal Liberation, bioethicist Peter Singer of Princeton University launched what became known as the animal-rights movement. The ability to suffer, he argued, is a great cross-species leveler, and we should not inflict pain on or cause fear in an animal that we wouldn’t want to experience ourselves. This idea has never met with universal agreement, but new studies are giving it more legitimacy than ever. It’s not enough to study an animal’s brain, scientists now say; we need to know its mind.

Jeffrey Kluger, Inside the Minds of Animals, TIME, August 5, 2010