According to a new study, it appears that certain phobias can be manipulated and even banished while a subject sleeps. The study involved showing the participants a scary image accompanied by a smell.
The participants then took a nap during which time they were exposed to the smell. When they awoke, they were again shown the scary image. This time they were less frightened. Apparently their brains had learned to deal with the fear while being reminded of it with the smell while they slept.