In Marcus de Sautoy's video, The Secret you, he volunteers himself for a sleep study based on brain activity and consciousness. For the study he was given mild shocks to his brain while wearing equipment that measured his brain activity. While he was awake and conscious many different locations in his brain were active, even when the shock was distributed to a small area. Unfortunately, he couldn't fall asleep in the lab so they used a different subject's information while they were asleep. The results were that while sleeping, only small locations of the brain were active; whereas awake many were active.
This leads me to think that because we use less of our brains while we are unconscious, that might be why we tend to dream very unrealistic situations and think they are real, when in reality they are only a dream. The same goes for hypnosis, supposedly people become unconscious when hypnotized, therefore using less of their brain. All the hypnosis acts that I've seen, people tend to do extremely embarrassing and crazy things, nothing they would dream of doing while conscious. This, in part, may have to do with fact they are using less of their brain. If we were able to utilize our entire brain while asleep or hypnotized we may be able to realize what is happening and act accordingly; like realize we are dreaming and not be afraid or realize we are being hypnotized and not react to the hypnotist.
Have you ever had a dream that was unrealistic but seemed very real to you?