“The interpretation of dreams is the royal road to a knowledge of the unconscious activities of the mind,” Freud argued in his influential treatise The Interpretation of Dreams in 1900. “The earth is heavy and opaque without dreams,” Anaïs Nin wrote in her diary in 1940. “In the olden days, people believed that our dreams were full of clues about the future,” Alain de Botton told a little kid who wanted to know about dreaming. But what, exactly, are dreams and why do we have them? Modern psychology has given us a fair amount of insight on the creative purpose of daydreaming, but — aside from Rosalind Cartwright’s compelling research on how dreams and REM sleep mediate our negative emotions — the study of dreams has largely stagnated since Freud’s day.

In Dreamland: Adventures in the Strange Science of Sleep (public library) — one of the best science books of 2012, exploring what happens while you sleep and how it affects your every waking moment, which also gave us this fascinating read on sleep and the teenage brain — David K. Randall traces psychologists’ evolving understanding of why we dream.

Freud’s theories — premised on the idea that the symbolism of dreams encoded the dreamer’s subconscious desires and concerns, often of a sexual nature — were systematically challenged and dismissed over the course of the 20th century, but without much of a viable alternative theory. It wasn’t until Calvin Hall, a psychology professor at Case Western Reserve University, set out to record and catalog people’s dreams in the 1950s that glimmers of illumination began piercing the darkness shrouding this psychological mystery. Randall writes of Hall’s empirical findings, which came diametrically opposed to Freud’s theories:

By the time [Hall] died in 1985, Hall had synopses of more than fifty thousand dreams from people of all age groups and nationalities. From this large database, he created a coding system that essentially treated each dream like it was a short story. He recorded, among other things, the dream’s setting, its number of characters and their genders, any dialogue, and whether what happened in the dream was pleasant or frightening. He also noted basics about each dreamer as well, such as age, gender, and where the person lived. Hall introduced the world of dream interpretation to the world of data. He pored through his dream collection, bringing numbers and statistical rigor into a field that had been split into two extremes. He tested what was the most likely outcome of, say, dreaming about work. Would the dreamer be happy? Angry? And would the story hew close to reality or would the people in the dream act strange and out of character? If there were predictable outcomes, then maybe dreams followed some kind of pattern. Maybe they even mattered. Hall’s conclusion was the opposite of Freud’s: Far from being full of hidden symbols, most dreams were remarkably straightforward and predictable. Dream plots were consistent enough that, just by knowing the cast of characters in a dream, Hall could forecast what would happen with surprising accuracy. A dream featuring a man whom the dreamer doesn’t know in real life, for instance, almost always entails a plot in which the stranger is aggressive. Adults tend to dream of other people they know, while kids usually dream of animals. About three out of every four characters in a man’s dream will be other men, while women tend to encounter an equal number of males and females. Most dreams take place in the dreamers’ homes or offices and, if they have to go somewhere, they drive cars or walk there. And not surprisingly, college students dream about sex more often than middle-aged adults.

In other words, he found that dreams are far from surreal wonderlands where our imaginations roam wildly — rather, they are explorations of our mundane concerns, recast in a light only slightly removed from reality.

And yet theories continue to differ. Ernest Hartmann, a professor at the Tufts University School of Medicine, studies the content of dreams and how it relates to their function:

Hartmann sees dreams as a form of built-in nocturnal therapy. In dreams, he says, the mind takes what is new or bothersome and blends it into what the brain already knows, making the new information seem less novel or threatening. … Hartmann argues that the life of early man was filled with the kind of traumas — watching friends gored by animals with sharp tusks or fall through holes in the ice and drown, just to give you two possibilities — that few people experience today. Those who were able to regain their emotional balance after living through a traumatic event were more likely to survive over the long run than those who dwelled on the negative. As evidence of his theory, Hartmann points to the fact that the mind has a tendency to replay scary or harrowing experiences in dreams almost exactly as they happened in real life for several nights after the event. … For some people, however, the brain gets stuck replaying traumas, like a band that only knows one song. When the brain fails to set aside the event in its long-term memory — a move that researchers see as a sign that the emotional system has come to accept what happened and can now put it into perspective — a person may experience recurring nightmares, which is one of the hallmarks of post-traumatic stress disorder.

Grim as this may sound, however, let’s not forget that dreams also help us do the very opposite — they allow our brains to digest and regulate negative emotions. And, if all else fails, there’s always the option of training yourself to control your dreams.

Dreamland remains a must-read in its entirety. Complement it with the science of internal time.

Public domain images via Flickr Commons