Theory #1

The Evolutionary Theory: We Dream to Practice Responses to Threatening Situations

Ever notice that most dreams have a blood-surging urgency to them? In dreams, we often find ourselves naked in public, or being chased, or fighting an enemy, or sinking in quicksand. Antti Revonsuo, a Finnish cognitive scientist, has shown that our amygdala (the fight-or-flight piece of the brain) fires more than normal when we're in REM sleep (the time in sleep when we dream). In REM sleep, the brain fires in similar ways as it does when it's specifically threatened for survival. In addition to that, the part of the brain that practices motor activity (running, punching) fires increasingly during REM sleep, even though the limbs are still. In other words, Revonsuo and other evolutionary theorists argue that in dreams, we are actually rehearsing fight-and-flight responses, even though the legs and arms are not actually moving. They say that dreams are an evolutionary adaptation: We dream in order to rehearse behaviors of self-defense in the safety of nighttime isolation. In turn, get better at fight-or-flight in the real world.

Theory #2

Dreams Create Wisdom

If we remembered every image of our waking lives, it would clog our brains. So, dreams sort through memories, to determine which ones to retain and which to lose. Matt Wilson, at MIT's Center for Learning and Memory, largely defends this view. He put rats in mazes during the day, and recorded what neurons fired in what patterns as the rats negotiated the maze. When he watched the rats enter REM sleep, he saw that the same neuron patterns fired that had fired at choice turning points in the maze. In other words, he saw that the rats were dreaming of important junctures in their day. He argues that sleep is the process through which we separate the memories worth encoding in long-term memory from those worth