From Socrates and Descartes to Sigmund Freud and Carl Jung, history's best-known philosophers and psychoanalysts have weighed in on the subject.
Are dreams, as Freud and Jung believed, a window into our unconscious selves, or merely the not-so-meaningful by-products of sleep-related neural firings?
The question is still hotly debated by dream researchers, but most people outside the field seem to have made up their minds, shows a study published in the February issue of the Journal of Personality and Social Psychology.
Six separate surveys of very different populations showed that people tend to believe that their dreams reveal hidden truths about themselves and the world, says psychologist and study researcher Carey K. Morewedge, PhD.
In fact, the surveys showed that for many people dreams carry more weight than their conscious thoughts.
"People tend to think that dreams reveal hidden emotions and beliefs and they often find them to be more meaningful than thoughts they might have when they are awake," Morewedge tells WebMD. "But we also found that people don't attribute equal meaning to all dreams."
Dreaming Is Believing
In one study designed to determine if people from different cultures and backgrounds have similar beliefs about the meaning of dreams, Morewedge and colleague Michael Norton of Harvard Business School asked college students to rate different theories about the importance of dreams.
The survey group included science students from the U.S., economics students from India, and students in South Korea enrolled in a psychology class.
Across all three cultures, the vast majority of students endorsed the idea that dreams reveal hidden truths. This was also found to be the case in a survey of a nationally representative sample of Americans.
In a study designed to explore how dreams influence waking behavior, the researchers asked commuters in Boston to imagine one of four possible scenarios happening the night before a scheduled plane trip: consciously thinking about the plane crashing, hearing that the terrorist threat level had been raised, dreaming about a plane crash, or hearing about a real crash on the route they planned to take.
Dreaming of a plane crash produced the same degree of anxiety as hearing about an actual crash. Respondents said they would be more likely to change their travel plans after dreaming of a crash than after thinking about one or hearing that the threat level had been raised.
But another survey revealed that respondents were more likely to perceive a pleasant dream as meaningful when it was about someone they liked. Unpleasant dreams were considered more meaningful when the subject was disliked.
"We do see dreams as meaningful, but when they conflict with our existing beliefs and desires we tend to attribute less meaning to them," Morewedge says.
Dreams and Solving Problems
The researchers say more study is needed to fully understand how people interpret their dreams and whether they do actually reveal hidden information.
Behavioral psychologist Deirdre Barrett, PhD, has been studying dreams for more than a decade.
An assistant professor of psychology at Harvard Medical School, Barrett tells WebMD that she has come to believe that, like waking thoughts, some dreams are important and others aren't.
"Many of our waking thoughts are really trivial and repetitive and some are profound and meaningful," she says. "I think dreams are the same way. Some may reveal hidden truths, but some are just noise."
Barrett's own research suggests that dreams can be a useful tool for problem solving.
In one study, Barrett asked a group of students to think about a particular homework or personal problem that they needed to solve as they drifted off to sleep.
The students kept notebooks by their beds and were asked to try to recall their dreams when they first woke in the morning before thinking about anything else.
Over the course of a week, about half the students reported that they dreamed about the problem and half of these students said they dreamed a solution to the problem.
Barrett says there are countless anecdotal reports of dreams helping people solve problems, including two Nobel Prize winners who claim their breakthroughs came to them in their dreams.
Nobel laureate Otto Loewi famously credited a dream for providing the experiment that allowed him to prove that the transmission of nerve impulses was chemical and not electrical.
And World War II general George S. Patton publicly said that he came up with battle plans in his dreams.
"These are anecdotes, but they come from areas where you would not expect people to exaggerate the importance of a dream," Barrett says. "Scientists and generals don't get brownie points for having dreamed their ideas. They are more likely to get made fun of."