It may seem obvious to you what a dream is; and, for most everyday purposes, it is obvious. However, when performing research on dreams and dreaming, it’s essential that researchers have a clear and precise definition because what goes on in the mind during sleep varies as much as it does when we are awake (Pagel, Blagrove, Levin, et al., 2001). If a dream is defined simply as whatever people remember about their mental activity when they were asleep (e.g., Schredl & Wittman, 2005), virtually anything that occurs in the mind can be considered to be a dream. Much of this mental activity, however, is similar to what we experience during the day when we let our minds wander: relatively isolated thoughts and images “drift by” in an unorganized manner. A narrower definition will be used in this section: a dream is defined here as mental activity consisting of sequences of complex hallucinatory experiences during sleep that:
- are accepted by the person as actually happening;
- change during a single episode of dreaming.
In other words, a dream is a story consisting of imagined sights and sounds that the sleeping person believes are really 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 this happens, 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, conclude that a sleeping dog that barks and moves also may be dreaming.
Nevertheless, it may be a case of overgeneralization (an inference that is not justified based on the available evidence) to infer that dogs are having dream-like experiences based on human dreaming. It could be that their movements and noises are merely reflex actions caused by the activation of particular brain structures. The best way to know for sure would be to ask dogs; and, of course, they cannot answer our questions. There are other ways, however, to get evidence that animals dream. For example, experimenters have removed in cats the brain stem structure that “paralyzes” the body during REM sleep (Jouvet, 1999). These cats moved about their cages during REM sleep, apparently stalking and attacking prey in their dreams.
It’s very difficult to scientifically study dreams in humans because, in trying to be empirical — in attempting to observe dream events directly — it’s possible that we may change subjects’ dreams. Let’s call this the observation effect, and define it as changes that occur in a phenomenon when research participants know they’re 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 some other animals) often are aware that they’re being observed. As researchers, we must always try to determine if participants’ awareness 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 [reference]. 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 each person’s dreams tend to be to be similar from one night to the next, at least for short periods of time. One reason is that our dreams often reflect the concerns and experiences we have 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 (Freud, 1952). 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.
Dreaming also occurs during NREM sleep (Suzuki, et al., 2004): perhaps as much as 50% of the time in Stage 1 and 10% of the time in Stage 2 [reference]. Although this is less frequent than the 85% dreaming that occurs during REM sleep, it’s still a significant amount of dreaming. During the 1950s and 1960s, most sleep researchers believed that dreaming occurred only during REM sleep. For example, William Dement, a well-known sleep researcher who began his work in Nathaniel Kleitman’s sleep laboratory in the 1950s, stated that very few dreams occur during NREM sleep and, as evidence, presented 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” (Dement and Vaughan (1999) p. 293). The fact that he didn’t recall any dreams , however, is not good evidence for the claim that people, in general, don’t dream during NREM. Perhaps there was something unique about the characteristics of his NREM sleep. Furthermore, we don’t know from which NREM stages he was awakened. If they were Stages 3 and 4, then it wouldn’t be surprising that he remembered no dreams: little or no dreaming occurs during SW sleep. (See my blog post here for more about why anecdotes are not good evidence for claims.)
Dement offered another anecdote as further 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 & Vaughan, 1999). Dement then served as the subject so that he could show the other student the connection between REM sleep and dreaming. The student awakened him five times during the night, but Dement was 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, this may not be true of people in general.
The results of some studies suggest that the characteristics of REM dreams don’t differ from NREM dreams (Rosenlicht & Feinberg, 1999), whereas the results of other studies suggest that they do (Suzuki, et al., 2004). The studies that find differences report that REM dreams are more vivid, have more emotional content, and may be more bizarre. Nevertheless, not all agree that such differences exist. For example, David Foulkes (1996, 1999) argued that dreams are simply what happens at the conscious level whenever the brain is highly active during sleep: 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” (1999, p. 2). In other words, Foulkes claimed that we dream whenever three conditions occur:
- our brains are highly active;
- we are relatively unaware of the world outside of our bodies;
- we are unable to control the direction of our thoughts.
These three conditions occur during Stage 1, Stage 2, and REM sleep, and so, Foulkes concluded that the characteristics of dreams are similar in all three stages. The question is not yet settled, however, and research on REM versus NREM dreaming continues.
Study Questions for Section 2-11
- How would you define a “dream” in your own words?
- When would a series of images and thoughts occurring during sleep NOT be an example of a dream?
- What is some evidence that animals other than humans dream during sleep?
- What happens in sleeping cats when the part of the brain stem that paralyzes the body during REM sleep is removed?
- What is meant by the term “observation effect” and why is it of concern to researchers who study human and animal behavior?
- What is Freud’s concept of the “day residue” and what does it suggest about the meaning of dreams?
- What is the main problem with using anecdotes to support claims?
- During which stages of sleep do we dream the most?
- According to David Foulkes, why do we dream so frequently during these stages?
- What do research results tell us about possible differences between REM and NREM dreams?
Practice Quiz for Section 2-11
References
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