Sleeping helps us reset our brains and calm our emotions. Perhaps it can do more, though: if sleepers are exposed to odours they associate with bad memories, it appears they can lose the fear those memories bring.
Previous studies have shown that sleep helps eliminate fear in general. But whether it is possible to focus this effect through the careful use of odours has not been tested in humans.
Katherina Hauner and Jay Gottfried of Northwestern University in Evanston, Illinois, exposed subjects to four pictures of faces and a series of inoffensive smells such as mint. When one of the faces appeared, the volunteers got a painful electric shock.