Carey Mulligan Freezes Her Head Off in Sundance

Carey Mulligan may have been under the false impression SUN-dance did not require headgear, but she learned a hard lesson Saturday during the famous film festival.

Carey left the hotel without headgear, which she clearly soon regretted. She braved the 20 degree cold to see the sights, along with Zoe Kazan, the screenwriter who wrote "Wildlife" in which Carey stars.

Carey is in Sundance promoting her film, "Wildlife" ... based on a 1990 novel about a boy who watches his parents' marriage fall apart.

The Sundance Film Festival goes until a week from today.