Studies show that you can bring about a dream in another person. One way is by holding an open bottle of perfume under the sleeper's nose. Another is by whistling. A third way is by blowing air across the sleeper's face with a fan. Someone else can also affect the content of a sleeper’s dream. For example, turning on a light produces happier dreams. And darkening an already bright room can induce nightmares.

What would happen if I was prevented from dreaming?

In a study conducted by Dr William Dement, a professor of psychiatry at Stanford University, it was found that dream deprivation produces anxiety, irritability, an inability to concentrate, paranoia, a ravenous appetite, depression, and even suicidal thoughts. The study was very simple. Volunteers were assigned beds in a laboratory. Researchers observed them closely for five nights. Each time a subject's rapid eye movements indicated they were starting to dream (REM sleep), the researchers would wake them up and keep them from dreaming. It seems that it only takes a few days of dream deprivation before the symptoms begin to occur.

Why can’t I remember all of a dream?

How much of a dream we remember depends upon how soon we awaken after the dream. In one study, sleeping subjects were awakened while they were dreaming in REM sleep. Other sleeping subjects were awakened 15 minutes after they were in REM sleep. In 152 out of 191 cases, the subjects awakened during REM sleep remembered they were dreaming and could recall a great deal of content of their dreams. Hardly any of the subjects awakened 15 minutes after their REM sleep could remember dreaming at all. If you’re awakened during or shortly after REM sleep, you’re probably more likely to remember more of your dream.

Stephen Juan, Ph.D. is an anthropologist at the University of Sydney. Email your Odd Body questions to s.juan@edfac.usyd.edu.au