In the last few decades, scientists have conducted much research with regards to the functions of sleep and dreaming. Although the primary function of sleep is unknown, scientists have shown through experimentation that sleep is a biological requirement in most animals.
In contrast, the function and importance of dreams are still widely debated. Possible functions of dreams posed include developmental, evolutionary, and psychological, and these functions carry physical, mental, and social health implications. A few neural correlates have been linked to dreaming, particularly those involved in rapid-eye movement, or REM sleep. Furthermore, three main explanations have developed as to why dreams occur: psychoanalytic, psychobiological, and cognitive.
The psychoanalytic theory was developed in the early years of psychology, with Freud at the forefront. The psychobiological theory, on the other hand, takes a more biological approach dominated by empirical research; the neural correlates that have been linked to dreaming are the basis for much of the psychobiological theory. The third explanation, called the cognitive model, is more dynamic than the psychoanalytic or psychobiological models; this explanation blends ideas from both of the previous models, and also incorporates the consolidation hypothesis, which explains a possible function for sleep.
The consolidation hypothesis was developed from Jenkins and Dallenbach’s (1924) experiment in which they tested the functions of sleep in regards to learning. They found that subjects who were allowed to sleep after learning something new had better memory retention than those who were denied sleep. The researchers believed that sleep aids in the consolidation of new information, which allows for a faster and more accurate retention rate of information (Dallenbach, 1924). Although the cognitive explanation for the function of dreams utilizes empirical data for support, it also employs the consolidation hypothesis in order to help explain and interpret the empirical research that has been done pertaining to dreams. While all three theories make compelling arguments as to the possible function of dreams, the cognitive model seems to be the most plausible, combining elements from the other theories and providing a new model with which to look at dreams and their importance.
Louis Breger proposes three purposes for dreams in the Journal of Abnormal Psychology. The first purpose is of a developmental nature. He points to an article from 1966 that suggests REM sleep is important in the early stages of the central nervous system’s (CNS) development. In the article, entitled ‘Ontogenetic Development of the Human Sleep-Dream Cycle,’ Roffwarg and colleagues claim that REM sleep’s main function during development is to facilitate the maturation of the CNS; in fact, infants spend roughly 50% of their time in the REM sleep stage. Roffwarg’s team hypothesizes that there is an ‘endogenous stimulation’ (Breger, 1967, p. 2) that occurs during REM that affects CNS development in a positive way. Since much of dreaming occurs during REM sleep, it could be implied that dreams play a crucial role in the beneficial stimulation of CNS development. This developmental role dreams play has some mental and physical health implications; if the CNS does not develop properly, for example, the individual could be stricken with a number of CNS disorders that affect mental and physical development.
When looking at the evolutionary function of dreaming, Breger references a 1966 article written by the chief of psychophysiology of sleep at the National Institute of Mental Health (NIMH) during the 1960s. Dr. Frederick Snyder (1966) suggests that REM sleep, during which dreams occur, is a crucial, preparatory state for organisms. REM acts as a multi-tasking watchman; it allows the organism to engage in much-needed sleep, while also keeping a close eye out for signs of imminent harm (Snyder, 1966). Because REM sleep is characterized by brain waves that closely match the waves of an alert organism, it allows the organism to awake suddenly and somewhat alertly if needed. This semi-alert state that dreams provide during REM have some physical health implications. For instance, organisms that dream might awaken more quickly in response to danger than those that do not dream, and this quick response to danger gives organisms that do dream an evolutionary advantage.
Breger also proposes a psychological function for dreams, a function that relates both the developmental and evolutionary aspects of dreaming to the psychological reasoning behind why dreams occur. Breger (1967) suggests that REM sleep sets the stage for the function of dreams later in life, which is to help ‘integrate recent perceived input into existing internal structures’ (p.4). According to Breger, the maturation from REM sleep to complex dreaming is a psychological one, and in order to understand the psychological function of dreams, one must look at the theories that have developed behind why dreams occur.
Psychoanalyst Sigmund Freud, author of The Interpretation of Dreams (1899/1911), was one of the first psychologists to address a function for dreams. Freud believed that all dreams could be interpreted based upon his psychoanalytic theory, also known as Freudian psychology. Freud developed his theory around the workings of the mind, which he compartmentalized into the conscious and unconscious mind. Additionally, his theory includes explanations as to the psychosexual development of humans based upon the three components of human personality: the id, the ego, and the superego. According to Freud, much information could be learned about a patient’s personality and desires by conducting dream analyses.
To Freud, the ability to interpret dreams is a beneficial one, because a dream contains key information about the physical, mental, and social health of its beholder. Freud develops his psychoanalytic theory of dreaming in The Interpretation of Dreams by first criticizing ancient theories that explain the existence of dreams. For example, Freud (1899/1911) criticizes German physiologist Karl Friedrich Burdach, who believed that dreams have absolutely nothing to do with the waking state; on the contrary, Freud believes that dreams materialize due to a lack of contentment in the waking state. During Freud’s therapy sessions, patients would recount dreams and he would analyze them. Particularly, Freud analyzed the dreams for any underlying feelings or repressed desires that may be unacceptable to voice in a conscious state. Through this type of dream analysis, Freud noticed that certain words have other meanings that signify thoughts or wishes that might not be appropriate to express in a conscious state. For example, Freud (1899/1911) believed that the word house signified the human body, while the word bath signified birth. By identifying these dream symbols, Freud could determine the underlying problem in his patients’ lives. Thus, Freud believed that dreams served as a medium through which the unconscious psyche could make its desires known (1899/1911).
The psychoanalytic theory, in terms of its explanation for the function of dreams, has received much criticism from the psychological field. While Freud makes many intuitive claims based on the patients he treated, he provides no real empirical evidence to support his claims.
In fact, much of Freud’s early work in the field of psychoanalysis has been discredited due to lack of scientific data. In his 1996 book, Why Freud was Wrong: Sin, Science, and Psychoanalysis, Richard Webster examines Freud’s childhood, relating Freud’s deep religious background to the faulty science of Freud’s later years. He claims that Freud developed his theories according to divine dreams from his childhood, and lacks any concrete data to support his psychoanalytic theories (Webster, 1996). Although Freud makes an interesting argument as to the function of dreams, his theory lacks empirical evidence and thus should not be considered as the primary explanation behind the purpose of dreams.
In contrast to Freud’s psychoanalytic theory, the psychobiological theory for why dreams occur is founded upon modern, empirical evidence. Instead of looking solely at the behavior of subjects, as in the psychoanalytic approach, the psychobiological approach aims to empirically connect the biological and physiological components associated with dreams to explain their function. Through these empirical studies, scientists have discovered specific areas of the brain that are involved in dreaming. Allan Hobson, a psychiatry professor at Harvard Medical School, has conducted extensive research concerning sleep and dreams in order to better understand the role of dreams. In his 2000 article ‘Dreaming and the brain,’ Hobson empirically shows that there is a distinct difference between REM sleep and the waking state. Hobson and colleagues (2000) employed neuroimaging to look at the physiological differences that occur between REM sleep and waking. This type of experimentation is novel and important because it provides a more advanced look at the brain’s involvement during sleep, dreaming, and waking. For example, PET studies have shown that during REM sleep, there is a ‘preferential activation of limbic and paralimbic regions of the forebrain’ (Hobson, 2000, p. 808); this finding has replaced the older theory that a generalized activation of the forebrain occurs when individuals are sleeping and dreaming.
In the psychobiological theory, empirical studies are utilized to understand what is physiologically occurring when subjects are asleep versus when they are awake. Although the psychobiological theory provides solid evidence as to the biological aspects involved in dreaming, it fails to adequately explain the psychological reasons behind why dreams occur. It is more scientifically accurate than the psychoanalytic theory, yet it does not provide sufficient reasoning as to the social, physical, and mental health reasons why dreams exist, and thus is not an acceptable theory to explain the function of dreams.
A third theory that explains the function of dreaming is the cognitive model. This model incorporates elements from the consolidation hypothesis that explains the function of sleep, as well as elements from both the psychoanalytic and psychobiological theory. In his book, The Scientific Study of Dreams: Neural Networks, Cognitive Development, and Content Analysis (2002), Dr. Domhoff outlines the various empirical methods with which dreams have been studied as scientific advances have been made in fields like neuroscience, psychology, and psycholinguistics. In fact, the field of psycholinguistics has greatly aided psychologists who are interested in understanding dreams. David Foulkes of Emory University (1982) suggests that the cognitive way in which scientists have studied linguistics should be implemented when studying dreams. Aside from linguistics, Domhoff also sheds light on various observational studies that have been conducted with respect to dreams; he shows that dreams are often unchanging and repetitive, and they often portray topics with which the dreamer is preoccupied (2002).
Domhoff’s work is just one of many examples of how the cognitive model attempts to explore the function of dreams. It is a fluid model that is able to incorporate new findings and information as science and the technology used to study dreaming advance. Based upon observational studies, the cognitive model theorizes that dreams sift through unimportant, non-essential subjects and help the dreamer to focus on more important topics, including new things that the individual has learned or issues that the dreamer deems significant (Domhoff, 2002). The cognitive theory is backed by empirical research, like the psychobiological theory, but the cognitive model is also backed by many legitimate observational studies, including dream journals and other individual studies that are much more certifiable than Freud’s dream analyses. The cognitive model thus seems to present an unbiased, thorough explanation as to the function of dreaming, making it the most plausible of the three theories for the function of dreams.
Psychologists have made many advances towards the discovery of the function of sleep and dreams. Through observational and empirical research, they have found that sleep is an important, necessary process in most animals. The importance of dreams, however, is a more debatable issue due to the lack of tangible, substantial evidence in favor of its advantages and overall functions. Researchers have proposed developmental, evolutionary, and even psychological benefits to dreams, and three major theories have developed regarding the function and overall significance of dreams.
The earliest theory to emerge, Freud’s psychoanalytic theory, takes an observational approach to identifying the function that dreams serve. Freud theorized that dreams are the result of unfulfilled wishes or desires in the subject’s life. If the dreams are properly analyzed, he proposed, then they can provide great insight into the subject’s needs and be used to the subject’s advantage. This possible function for dreams poses many physical, mental, and social health implications; if dreams are the medium through which the subconscious mind speak, then they could play a beneficial role in the subject’s life and well-being. While Freud’s psychoanalytic theory serves as a good starting point when thinking about dreams in terms of their function, it is not a very realistic theory; there is no empirical evidence to support Freud’s claims, and most of his analyses are purely subjective, not objective.
The psychobiological theory focuses on the biological interactions associated with sleep and dreams based on verifiable, empirical evidence. In fact, the theory relies on experimental findings to confirm the biological processes that are activated during sleep, particularly during REM sleep when dreams occur. While the theory is supported by many research experiments, and scientists have learned a considerable amount about the various biological and chemical correlates involved in dreaming, the theory does not provide a sufficient explanation as to the primary function of dreams. Thus, the reasoning behind why dreaming occurs cannot be explained solely by the psychobiological theory.
Scientists have developed a third theory as to the function and importance of dreams, named the cognitive theory. This theory seems to blend components of Freud’s psychoanalytic theory, the psychobiological theory, and the consolidation hypothesis proposed by Jenkins and Dallenbach that describes the function of sleep. The cognitive model is partly based upon research that scientists have conducted using advanced technology to identify the specific parts of the brain that are engaged during sleep and dreaming. The cognitive theory goes one step further than the psychobiological theory, however, by not only determining what is going on in the brain when individuals sleep, but also by theorizing the reasons behind why dreams occur. Currently, scientists for the cognitive model believe that dreams occur according to the consolidation hypothesis (Dallenbach, 1924); dreams are a way of reinforcing and remembering new information that has been learned or information that the individual deems important (Domhoff, 2002). Additionally, scientists have compared the findings and advances in psycholinguistics to the expanding field of the study of dreams and their associated processes and functions.
Psychologists still have much to learn about dreams in the way of their functions and importance, and future experimentation in the field is needed in order to better characterize the role dreams play in the dreamer. Further research should be conducted on the physiological processes that occur during dreams, particularly during the REM stage of the sleep cycle. Scientists should research the molecular aspects governing dreams, paying special attention to the cellular interactions that are required for dreams to develop. Moreover, researchers should further identify and characterize any dreaming differences seen in subjects who suffer from sleep disorders like narcolepsy and insomnia as opposed to healthy individuals. These are just a few of the many research experiments that could be formulated in order to better understand the function of dreams.