Teacher Resource: Handout

Why do scientists think we have dreams?
And where do they think dreams come from?

One of the most widely-accepted scientific theories about dreams is J. Allen Hobson’s Activation-Synthesis Hypothe sis . Hobson, a Harvard neuroscientist, believes that dreams start out as random electrical sparks during REM in the brainstem. He says that the electrical activity causes weird, disconnected images and sensations in our minds. The cortex ("higher" area of the brain which handles complex thought) then tries to make sense of the jumbled input, resulting in a dream.

Many other scientists agree with Hobson, believing that random activation of the brain is responsible for creating dreams. Our brains may need to stay somewhat active during the night, so the theory goes, so that we are alert enough to wake up if there is danger. (During REM sleep, our brainwaves do speed up and look more like our waking brainwaves.) Or the random stimulation may simply be "exercising" the neural pathways to keep the connections strong. Dreams may just be an "accident" or a "by-product" of this exercise process.

Other scientists argue that REM sleep and/or dreaming may be essential for learning and memory . They believe that we may actually be building new physical or chemical connections within the brain as we dream in REM sleep. Harvard’s Robert Stickgold and Trent University’s Carlisle Smith are two of the researchers investigating this idea. Our dreams may be an odd way of "eavesdropping" on the work that the brain is doing as it processes new information and consolidates it in memory, connecting it to older, previously-stored information.

Crick & Mitchison’s Unlearning Theory says exactly the opposite, that dreams don’t help us remember; they help us forget trivial and useless information. This unlearning supposedly clears out mental space, allowing us to re-use neural pathways to store new memories.

Still other scientists (such as Rosalind Cartwright) suggest that dreams aren’t intellectual at all; rather, they are triggered by our emotional reactions, and that they may be necessary for us to regulate our mood . Researchers such as Milton Kramer and Ernest Hartmann believe that dreams result from unresolved emotional issues that surface during sleep.