The word "dream" has four interrelated meanings that follow one from another. When we put them altogether, we know what a dream is.
First, a "dream" is a form of thinking that occurs when (a) there is a certain, as yet undetermined, minimal level of brain activation, and (b) external stimuli are blocked from entry into the mind, and(c) the system we call the "self system" (the "I," the "me") is shut down. This may seem overly complicated, but it is worded this way because we don't just dream during sleep, but also on some occasions in very relaxed waking states when we "drift off" and suddenly realize we have been dreaming. Two careful studies have shown that people are awake (by EEG criteria) during these episodes. (The fact that we don't need to be asleep in order to dream may have some important implications. For example, it favors a "cognitive" theory of dreams over theories that talk about neurophysiological or neurochemical changes during sleep that supposedly produce dreams.
Second, a "dream" is something we "experience" because the thinking is very real and makes use of our senses -- especially seeing and hearing; because usually we are the main actor; and because a dream is sometimes very emotional (but not always).
Third, a "dream" is what we remember in the morning, so it is "a memory" of the dreaming experience.
Fourth, a "dream" can also mean the spoken or written "report" we give to others about that experience, which is the only way anyone else can ever know about another person's dreams (because they can't be seen by others or told about by us while they are happening).
So, to sum it all up, we can think of a "dream" as a report of a memory of a cognitive experience that happens under the kinds of conditions that are most frequently produced in a state called "sleep." But if you want it to be more simple, you can think of dreams as the little dramas our minds make up when the "self" system is not keeping us alert to the world around us.
Why do we dream? Do dreams have a function or "purpose"?
No one knows for sure. Click here for further discussion.
How often do we dream, and when?
Most people over the age of 10 dream at least 4 to 6 times per night during a stage of sleep called REM (for Rapid Eye Movements, a distinguishing characteristic of this stage of sleep). During REM periods our brains become as active as they are during waking, although not all parts of the brain are reactivated (the parts of the brain that are reactivated in REM are discussed in Chapter 1 of Domhoff's The Scientific Study of Dreams (2003)). REM periods vary in length from 5 to 10 minutes for the first REM period of the night to as long as 30-34 minutes later in the night. It thus seems likely that dreams can be a half hour or more in length.
There is also evidence that we can dream in non-REM sleep in the hour or two before waking up, when the brain has become more activated than it was earlier in the night. That's why we said that we dream "at least" 4 to 6 times per night.
But there are further qualifications that need to be added. Sometimes we can have dreamlike moments during waking if we are in a relaxed state of mind and not noticing anything in our surroundings, as demonstrated in two different studies of people awake in slightly darkened rooms who were signaled at random intervals to say what was going through their minds. And the investigators knew these people were awake because their brain wave activity was being monitored via EEG. So, it may be that we dream any time that the following conditions are met: (1) an adequate level of brain activation; (2) a shutting out of external stimuli; and (3) a shutting down of the self-awareness system that helps focus our minds when we are awake.
One final note: We said that these findings refer to "people over the age of 10." That's because two important studies suggest that children under age 10 only dream in about 20% of their REM periods (again, see Domhoff, 2003).
In summary, we can dream in REM or non-REM sleep, and perhaps even during waking, but we also can have REM sleep without dreaming.
Do all dreams contain a hidden meaning?
That question doesn't have a definitive answer. Some people would say yes, and we'd have no way of proving them right or wrong. Some dreams may well contain "hidden" meanings in the form of metaphors or symbols, but an awful lot of dreams are just mundane "doodles" taken from the events of our lives.
I keep having this one dream that repeats over and over. Should I be concerned?
No, most people have recurring dreams of one kind or another. Furthermore, there's much more repetition in dream content than most theorists realize. For further information on the "repetition principle" in dreams, click here.
I had a dream that I was being chased or attacked. What's going on?
No one knows for sure, but if it is any solace, almost everyone has such dreams.
Are dreams influenced by fears or stress? Any other factors?
Most definitely. Dreams often express our current concerns and preoccupations; we call this "the continuity hypothesis." If you are nervous about studying for finals, you may have nervous dreams on the same topic. Dreams are not always about negative preoccupations, though. If you have a crush on someone, it is likely that you will dream about them; if you love basketball, you're more likely to dream about it than someone who doesn't follow the sport.
Do drugs influence dreaming?
At the least, they often make dreams more vivid and scary, as seen best when L-dopa is given to those suffering from Parkinson's Disease. However, there are no large-scale studies showing if and how specific drugs may influence dream content. For an interesting pilot study on how an SSRI (selective serotonin reuptake inhibitor) affected the dreams of a young woman suffering from anxiety attacks, along with references to past studies, click here.
Do animals dream too?
We can never know for sure. All we can measure is whether or not they have REM (rapid eye movement) sleep, which is more or less associated with dreams. All mammals have REM sleep, but that doesn't prove that they dream. Humans don't always dream during REM (and what's more, some dreams happen outside of REM). For more information, look up the following informative article by David Foulkes:
Foulkes, D. (1983). Cognitive processes during sleep: Evolutionary aspects. In A. Mayes (Ed.), Sleep mechanisms and functions in humans and animals: An evolutionary perspective (pp. 313-337). Wokington, UK: Van Nostrand Reinhold.
Do blind people dream? If so, what are their dreams like?
Yes, blind people dream, and it is a testimony to the highly visual nature of most people's dreams that this question gets asked. For a paper that provides information on the dreams of one group of blind people, along with references to most of the literature on blind people and dreams, click here.
What are the dreams of children like?
If sleep lab studies where children are awakened throughout the night can be trusted -- and we think they can -- then children's dreams are less frequent and more bland than popular stereotypes suggest. But children are probably pretty good dreamers by the 5th grade. To see some samples of dreams from children of various ages, look in the DreamBank. To read a study of the dreams of 7th grade boys and girls, click here.
Are dreams collected in a sleep lab very different from those remembered at home (presumably because people are "on guard" in the lab)?
We once thought so, but several studies showed otherwise, and then we did a reanalysis of some of Hall's early data on the question that showed very little difference. Click here to read the analysis.
I've been writing down my dreams. What's a good way to study them that doesn't involve scary statistical analysis or flaky stuff about symbolism?
Calvin S. Hall developed a good and simple method based on themes. Click here to read an article about it.
Why don't I remember more dreams?
There's no one final answer so far, just several little ones. Keep reading to learn more.
Why are dreams so forgettable?
It seems likely that all of us forget 95-99% of our dreams for the very ordinary reason that we sleep right through them and aren't paying attention to remembering anything. One dream researcher suggests that it's similar to when you are doing something that doesn't take much concentration, such as driving on an open road, so you are not paying attention to what you are doing.
Can you predict who will recall a lot of dreams and who won't?
In studies that compare people who recall several dreams a week with those who recall one a month or less, the biggest difference is that the people who recall have a greater interest in dreams and therefore a greater motivation to pay attention to them. For some reason, these people have decided that their dreams are worth remembering. Sometimes it is because they had one that seemed to come true, or one that fascinated them. The main reason we know "interest" and "motivation" are important is the high recallers say on surveys that they think dreams are important. But we also know it because some low recallers are stimulated to recall when they read about dreams or take a class on them.
Are there other mental or personality factors that influence rate of recall?
Some low recallers seem to be less good at tasks involving visual imagination, such as when they have to look at a picture of a building made of blocks and then construct one out of blocks that are sitting in front of them. There may be other "cognitive skills" relating to the ability to imagine things that are important, too, but the research is not yet completely convincing on this point.
As far as personality factors, which many people might think to be the main factor, studies using several personality tests don't show either large or consistent relationships. Nor is there any evidence that some people are too "defensive" or "repressed" to remember their dreams. Several studies are pretty convincing on that point.
What does it mean if someone recalls an excessive number of dreams, or no dreams at all?
In extreme cases of excessive dream recall, or no dream recall at all, there may be chemical imbalances at work. We think we know this because some medications lead people to report to physicians that they are remembering more dreams, and that the dreams are very vivid and realistic, and sometimes very scary.
In extreme cases of no recall, still another thing may be going on. These people may be dreaming very little or not at all. That probably sounds unlikely to most of you who heard growing up that everyone dreams at least during the four or five Rapid Eye Movement (REM) periods of the night. But the people who did that research in the 1950s and early 1960s may have jumped the gun a little because they hadn't studied the full range of people. Based on recent studies, including one using low recallers who were very low on visuospatial skills, it now seems probable again that some people don't dream.
Moreover, some people who suffer lesions in specific parts of the brain are known to lose their ability to dream for varying periods of time. These unusual cases show that it is possible to have the usual amount of REM sleep -- about 20-25% of the night -- and not dream. And to be mentally healthy without ever dreaming.
Young children don't seem to recall many dreams. Why is that?
There's evidence, based on over 1,000 awakenings during REM sleep in a laboratory setting, that children under age 9 just don't dream that much. Some people claim that their young children dream a lot, based on verbalizations they make during sleep, but this may just be "sleeptalking." We all have several little awakenings of a few seconds each night that we don't remember in the morning, and that may be when preschool children are doing some of the mumbling that is mistaken for dreams.
Can you recommend some good sources for learning more about dreams and dream recall?
G. William Domhoff, Finding Meaning in Dreams, Plenum Press, 1996, chapter 3.
David Foulkes, Children's Dreaming and the Development of Consciousness, Harvard University Press, 1999.
Mark Solms, The Neuropsychology of Dreaming, Erlbaum Associates, 1997.
What about non-scientific, "popular" sources?
Sorry, but we know of no "popular" books that are informative and accurate on this topic.
Can dreams predict the future?
No. We haven't seen any solid scientific evidence to support any age-old parapsychological claims about dreams, such as precognition, clairvoyance, or telepathy. Click here for a detailed account of the problems with paranormal research.
Can you die when you dream?
No; or rather, you're no more likely to die while dreaming than any other time. The rumor that "if you die in your dreams, you'll really die" is completely false. In fact, some "dying" dreams can actually be pleasant; see the following reference for more information:
Barrett, D. (1988). Dreams of death. Omega: Journal of Death & Dying, 19, 95-101.
Where can I find a list of dream symbols and what they mean?
There are many such lists, but we don't trust them. This is not to say that dreams don't have symbolic meaning; rather, everyone has their own set of symbols. We cannot endorse any claims by those who think they can analyze a single dream (or dreamer) on the basis of the objects contained therein. For an excellent article that traces the origins of dubious American "dream code" books back to the second century A.D. in Italy and Greece, see the following reference:
Weiss, H. B. (1944). Oneirocritica Americana. Bulletin of the New York Public Library, 48, 519-541. Reprinted in M. F. DeMartino (Ed.). (1959). Dreams and Personality Dynamics (pp. 29-44). Springfield, IL: Charles C. Thomas.
What do you think about the idea that there are symbols in dreams?
If you mean symbols that have one set meaning or foretell the future, we don't think there are such symbols (see above). Nor do we think that symbols provide a "disguise" for forbidden wishes, as Freud claimed. If there are symbols in dreams -- and that's a big "if" because there are as yet no convincing studies -- they are probably based on the same types of "figurative thought" used in waking life to create metaphors ("cross that bridge when you come to it," "don't burn your bridges") and slang ("she's a fox," "he's an ass"). For a serious paper by Hall that criticizes Freud's theory of dream symbols and presents a metaphoric theory that attempts to explain some -- and only some -- dream elements, click here
What's your best guess as to a comprehensive theory that explains dreams?
No one has developed a "perfect" theory yet. For Calvin S. Hall's cognitive theory of dreams from 1953 -- which is a very good start -- click here. For our more recent and comprehensive neurocognitive theory of dreams, click here.
What's your take on Freud and Jung's theories?
They were creative and plausible for their time, and they showed that dreams are a psychological phenomenon that has meaning, but systematic research does not support their specific claims. For a summary of our view, click here.
What about the activation-synthesis theory; i.e., that dreams are just the reaction to brainstem activation, and therefore without inherent meaning?
We very much doubt this theory based on a variety of findings. Click here for a critique of activation-synthesis theory (among others).
What do you think of Patricia Garfield's ideas about "Universal" dreams?
Not much. For Bill Domhoff's detailed critique of her 29 categories, click here.
Is there anything to Ernest Hartmann's claims about "contextualizing images" in his book on Dreams and Nightmares (1998)?
We think much more research is needed on the idea with a more reliable coding system than is being used now. This is especially so for the coding of emotions in dreams. Click here for a detailed critique of Hartmann's methods.