The Function of Dreaming
By Robert Stickgold
The search for the meaning of dreams dates at least to the biblical story of Joseph and The Iliad of Homer. The Book of Genesis quotes Joseph as saying, “The dreams of Pharaoh are one and the same. God has revealed to Pharaoh what he is about to
do.” The ancient Greek poet describes how Jove sent a lying dream to King Agamemnon,
telling it to “say to him word to word as I now bid you.” This view of dreams as messages
from the deities held sway for at least 4,000 years.
Sigmund Freud’s The Interpretation of Dreams, published in 1899, upended this assumption. For Freud, the father of psychoanalysis, dreams were a “safety valve” for the release
of unconscious excitation that would otherwise awaken the individual. But his book made
its mark less for how he thought dreams worked and more for what he thought they signified: disguised reflections of forbidden desires. His theory of dream interpretation captured the imagination of a sexually repressed Europe and became a metaphor for the dark
side of human nature. Indeed, Freud’s take permeated Western culture and wound up the
dominant explanation for dreaming and a favorite trope in the arts.
But Freudian dream theory never gained any respectable scientific evidence and prevailed for a relatively brief 75 years. In 1977, Harvard psychiatrists Allan Hobson and Robert McCarley unveiled their alternative: the Activation-Synthesis model. Dreams, they postulated, arise from a “largely random and reflex process” during rapid-eye-movement
(REM) sleep — the time when dreaming is most frequent and intense. Activation begins in
the pontine brain stem and spreads up to the visual cortex, leading to internally generated
imagery. This activation, “which is partially random and partially specific, is then compared with stored sensorimotor data in the synthesis of dream content.” Thus, the properties of dreams — their bizarreness, visual vividness, frequent depictions of movement —
all follow unavoidably from the neurophysiology and neurochemistry of REM sleep.