The mental activity that occurs during sleep does not always involve dreaming. Instead, some of this mental activity is similar to what we experience during the day when we let our minds wander: we experience relatively isolated thoughts and images that “drift by” in an unorganized manner. On the other hand, a dream consists of sequences of complex hallucinatory experiences during sleep that:

• are accepted by the person as actual occurrences,
• change during a single episode.

In other words, a dream is a story made up of imagined sights and sounds that, at the time, are believed by the person to really be happening (Kramer, 1994; Jouvet, 1999). We know that dreaming occurs in humans most often during REM sleep, and that almost all mammals and many species of bird go into a stage similar to the REM sleep of humans. Does this mean that all these animals are dreaming? You may have noticed that dogs sometimes make barking or yelping noises and twitch their paws during sleep. When we see this happen, many of us say, “he’s dreaming about hunting!” Perhaps we infer this because we know that, when we dream, we seem to be talking and moving, and therefore, we reason that a dog that barks and moves during sleep also may be dreaming.

Nevertheless, it may be a case of overgeneralization[∂] to use human mental experiences to infer that dogs are having dream-like experiences. It could be that their movements and noises are merely reflex actions caused by the activation of particular brain structures during sleep. The only way we could know for certain whether an animal was dreaming or not would be to ask it. Of course, dogs cannot answer our questions. On the other hand, some apes have been taught to use rudiments of language (by signing or pointing to pictures) to communicate with humans. After sleeping, one gorilla signed the phrase, “sleep pictures,” apparently in reference to the visual images seen during her dreams. If the structure in the brain stem that "paralyzes" the body during REM sleep is surgically removed in cats, they often will move about their cages during REM, apparently stalking and attacking objects in their dreams (perhaps hunting prey). Examples such as these suggest that other mammalian species dream (Jouvet, 1999).

It is very difficult to scientifically study dreams in humans because, in trying to be empirical — in attempting to observe directly the dream phenomena in which we are interested — it is possible that we may change the dreams that people have. Let's call this the observation effect, and define it as changes that occur in the phenomenon being studied when research participants know that they are being observed. If such an effect is influencing the results of a study, then our observations may not be telling us much about what actually happens out there in the “real world.” This is a potential problem in almost every study done in psychology because humans and many other animals often are aware that they are being observed. As researchers, we must always try to determine if the mere fact that participants are aware of being observed is having an effect on their behavior. In the case of dream research, some studies have shown that, in several important respects, dream reports gathered privately at home are similar to those gathered in the laboratory. This suggests that studying dreams in sleep laboratories is a valid way to develop and test theories about dreams and dreaming.

Some dream research has shown that there tends to be similarities in what people dream from one night to the next, for at least short periods of time. One reason for this is the fact that our dreams often reflect the concerns and experiences we had during the previous days and weeks; and to the extent that these issues are “on our minds,” we tend to dream about them. Sigmund Freud referred to the day-to-day concerns and experiences that make up our dreams as the day residue. People who experience emotionally intense events during their waking lives are likely to dream about them (or about related events) and to experience emotions consistent with these dreamed-about events. For instance, someone who has just experienced a divorce or the death of a family member may dream about losing something important (such as a diamond ring) and wake up feeling sad. The concept of the day residue suggests that dreams can be meaningful: they can reflect concerns, issues, problems, and experiences important to us in our everyday lives. On the other hand, it is unknown how much insight into our personalities and our problems we can gain by analyzing our dreams (see Section 2-12).

Research has shown that dreaming occurs during NREM sleep: as much as 50% of the time in Stage 1 and 10% of the time in Stage 2. Although this is less frequent than the 85% dreaming that occurs during REM sleep, it is still a significant amount of dreaming. What is most surprising about this finding is that, during the 1950s and 1960s, most sleep researchers claimed that dreaming occurred only during REM sleep. For example, William Dement, a famous sleep researcher who began to study sleep when he was a graduate student in Nathaniel Kleitman's laboratory during the mid-1950s, argued as late as 1999 that very few dreams occur during NREM (Dement, 1999). As evidence for this claim, he related the following anecdote[∂]: “In my early days with Nathaniel Kleitman, I often served as a research subject.... [I]n at least 100 awakenings from non-REM sleep, I never recalled dreaming” (p. 293). The fact that he didn't recall any dreams when awakened from NREM sleep is not good evidence that people, in general, don't dream during NREM: perhaps there is something unique about his sleep patterns. Furthermore, we don't know from which NREM stages he was awakened. If they were Stages 3 and 4, then it would not be surprising that he remembered no dreams: in general there is little or no dreaming during SW sleep. This example illustrates the problems with using anecdotes as evidence for claims.

Dement (1999) offered another anecdote as evidence for the claim that dreaming occurs primarily during REM sleep. In 1954, he quickly trained another medical student to identify REM tracings on an EEG. Dement then served as the subject so that he could show the other student the connection between REM sleep and dreaming. The student awakened Dement five times throughout the night, but Dement was completely unable to recall any dreams. By the fifth awakening, “I was so embarrassed and upset, I lied. I haltingly produced a phony dream fragment” (p. 293). It turned out, however, that the other student mistakenly had awakened Dement during periods of NREM, not REM sleep. Dement concluded that,“If anyone wants to claim that ... bias plays a role in the REM sleep-dreaming relationship, I could not have been more biased toward recalling a dream, and I was utterly unable to dredge up even a wisp of one” (p. 294). But again, anecdotes are not good evidence for or against a claim because they are affected by things such as the prior beliefs of the person telling the anecdote.

When controlled research on dreaming is performed, researchers generally find that dreaming occurs during NREM rather frequently, as already stated. Furthermore, they find that NREM dreams do not differ appreciably from REM dreams with respect to any characteristic such as the vividness of the dreams (Rosenlicht & Feinberg, 1999). Thus, it seems that we must reject the equation of REM sleep with "dream sleep." Instead, it seems that we can dream during any stage of sleep — most frequently during REM sleep, followed by light sleep (Stages 1 and 2). and very rarely in deep sleep (Stages 3 and 4). The finding that dreaming occurs most frequently in REM and light sleep suggests that high levels of brain activity probably are necessary for dreaming to occur.

In this vein, David Foulkes (1996, 1999) has argued that dreams are simply the workings of the conscious level of the mind whenever the brain is highly active during sleep. Foulkes (1999) stated that the “evidence suggests that dreaming is the form assumed by consciousness whenever there is residual ... [mind/brain] activation in the relative absence of direction either from the person’s environment or from voluntary self-control” (p. 2). In short, Foulkes claimed that we will dream whenever three conditions occur:

(a) our brains are highly active;
(b) we are relatively unaware of the world outside of our bodies;
(c) we are unable to control the direction of our thoughts.

All three of these conditions occur primarily during Stage 1, Stage 2, and REM.

Study Questions for Section 2-11

1. How would you define a "dream" in your own words?
2. When would a series of images and thoughts occurring during sleep NOT be an example of a dream?
3. What is some evidence that animals other than humans dream during sleep?
4. What happens in sleeping cats when the part of the brain stem that paralyzes the body during REM sleep is removed?
5. What is meant by the term "observation effect" and why is it of concern to researchers who study human and animal behavior?
6. What is Freud's concept of the "day residue" and what does it suggest about the meaning of dreams?
7. What is the main problem with using anecdotes to support claims?
8. During which stages of sleep do we dream the most?
9. According to David Foulkes, why do we dream so frequently during these stages?

Go to Quiz 2-11 questions

Go to Readings Section 2-12