In the book Stumbling on Happiness, author Daniel Gilbert mentions a little-known requirement for psychologists (like him). Apparently, at some point in a psychologist's career, they are required to write a sentence that begins "Human beings are the only animal that _________".

It's how they fill in the blank that matters, of course. And the more definitively you fill it in, he says, the more gleefully people will quote you after it's been proven wrong.

Tool use? Nope, not unique. Counting? Not unique. Altruism? Not unique. Abstract thought? Appears to be not unique...

What would you put on that blank?

Why do we mock people who want to give these simians rights?