One of the rats did a weird thing the other day, so I decided to look it up online. It turned out to be not very important. The fat one was doing a sort of waggly-irritated-tail-shimmy, which I correctly guessed meant the same thing in rat as it does in cat: That the owner of the tail has been briefly but profoundly annoyed when, for example, he wants to move but one of his less-bright littermates is sitting firmly on his head.

Every time I go look up something rat-related, I am again bowled over by how complicated and pernickety people can get about this. There are guides, pages and pages long, that purport to tell you how the rat feels about you by interpreting every last little nuance of his body language.

Do people really have a problem figuring this out? I never did.

Rats, you see, are terrible physicists. They're still ambivalent about gravity. Had Sir Isaac Newton been a rat, his first priority would have been eating his way into the free apple that had just plummeted down onto the ground where he could reach it, and by the time he went to sleep on the leftovers, 'investigate this whole falling bodies thing' would have slipped right off the end of the list.

Given their shaky grasp of classical mechanics, you can imagine that trying to explain to them that no two physical objects can occupy the same spatiotemporal coordinates is about as useful as trying to explain to them the concept that there is food out there in the world that isn't theirs -- it goes in one furry ear and out the other, without hitting anything in between. It's easy to tell how the rat feels about you, because a rat who likes you will make a sincere attempt to violate the Pauli Exclusion Principle as soon as you get within scritching range. He will try to become one with your hand, possibly stopping to test your watch for edibility first.

Anyone who has ever befriended a Labrador retriever already knows exactly how this works on the macro scale. Rats just drool less and leave fewer dents behind when they smack inattentively into the wall.