Rats! Humans, Rodents Have Lots in Common

Rats may be repulsive to some, but scientists are finding that they're a lot like humans. A recent crop of behavioral studies shows that rats are astonishingly self-aware, Natalie Angier reports in today's Times. They laugh when tickled and dream in epic narratives. There are even rat optimists and rat pessimists, their personalities forged by upbringing and environment.

Rats also know how to distinguish between good and bad sex, while giving every indication they look forward to the good kind, says one scientist. Rats are responsible for carrying deadly diseases, but only two species out of 120 are considered dangerous to humans. They also save human lives: Rats are the preferred experimental animal for vital medical studies. (More rats stories.)