Night bears. Our dog Laika dreams, which probably means that dreams date back at least to our common ancestor, which is a long long time ago. You can always tell -- her paws start twitching, and she whimpers. One time she even howled, which we can't even get her to do when we're awake. But I've always wondered whether they're happy dreams, or scary ones.

Usually she sleeps on her side. But last night, she fell asleep on the couch with me in an unusual position -- on her back. The practical effect of this was that her tail was freed up, and sure enough, when she started dreaming, her tail wagged. That can only mean that the dream, at least at the start, was happy. Isn't that sweet?