Dreaming LifeDreaming Life

The activation synthesis theory of dreams was developed by J. Allan Hobson and Robert W. McCarley of Harvard University, who explained their theory in an article in the American Journal of Psychiatry in 1977.  The activation synthesis theory says that dreams are caused by the brain trying to give meaning to random stimuli that take place during sleep.

Whereas psychoanalysis says that dreams have a psychological cause, the activation synthesis theory says that dreams have a physiological cause. Hobson and McCarley based this idea on the following observations - that all people have dreams, and that the dreaming phase of the sleep cycle happens at regular intervals and has a predictable length. This implies that dreaming is an automatically preprogrammed activity of the brain.

Hobson and McCarley said that during rapid eye movement (REM) sleep, the stage of sleep that is associated with dreaming, the pons, which is part of the brain stem, creates random stimuli. The forebrain, the seat of conscious thought, becomes activated. It then tries to synthesize a coherent story from these random stimuli. When possible, it uses thoughts held in short-term memory to help flesh out the story.

For example, suppose the pons creates stimuli that resemble the stimuli that are produced when you are running in waking life. Your mind will interpret this as running in a dream. Your mind may also incorporate any recent memories to help explain why you are running. If earlier in the day a large dog frightened you, you might dream that you are being chased by a wolf.

Hobson and McCarley said that the extremely common dream that someone is chasing you, but you can't move is probably your forebrain's way of explaining the fact that you really are paralyzed when you are dreaming.

Hobson and McCarley used research on cats to help develop their theory. They found that the pons continues to function and produce stimuli during sleep. They discovered that cats with large lesions in the pons stopped having REM sleep for several weeks, proof that activity in the pons is related to dreaming.

The activation synthesis theory explains why dreams can be bizarre and illogical and change very rapidly, with sudden shifts of scene and changes in people's identities. Because the stimuli from the pons are random and constantly changing, the forebrain constantly has to create new dream scenarios to explain them.

Psychoanalysis says that dreams take logical events and try to keep them repressed by making them seem illogical. The activation synthesis theory, on the other hand, says that dreams take illogical sensations and try to give them as logical an interpretation as possible.

Do Dreams Have Meaning?

According to the activation synthesis theory, your dreams are caused by random, meaningless events. However, the way your forebrain weaves these events into a story can provide meaning. As an analogy, think of a Rorschach (inkblot) test. Even though the inkblot was created randomly, without any intended meaning, the way you interpret the inkblot can provide insight on what is going on in your mind.

Criticisms of the Activation Synthesis Theory of Dreams

The activation synthesis theory explains why dreams can frequently change, in a bizarre manner. However, it does not explain why dreams can also have very complicated, coherent and sometimes extremely entertaining plots. It's hard to imagine how random activity from the brain stem can lead to the creation of such well-crafted stories. This theory also fails to explain how someone can wake up from a dream, then fall asleep again and continue having the same dream.

A major criticism of the activation synthesis theory is that it does not account for lucid dreaming. If the events in dreams are caused by random stimuli, how can lucid dreamers consciously control the events in their dreams? How can they carry out actions in their dreams which they planned before they went to sleep? According to Hobson and McCarley, when we move our eyes as we dream, we are responding to visual stimuli created in the pons. However, in laboratory studies, lucid dreamers have consciously moved their eyes during dreams according to pre-arranged agreements with researchers.