Faced with a rat trapped in a restrainer, a free rat opens the trap’s door to liberate the trapped animal (while stepping on its head — “very rat-ish behavior,” says University of Chicago neurobiologist Peggy Mason).

Faced with a rat trapped in a restrainer, a free rat opens the trap’s door to liberate the trapped animal (while stepping on its head — “very rat-ish behavior,” says University of Chicago neurobiologist Peggy Mason).