KeywordsDream Content Dream Equation Dream Interpretation Dream Research Neurobiological Approach
Dreams are a succession of vivid images, scenes, thoughts, and emotions that occur involuntarily in the mind in sleep, which the dreamer often experiences as something that is actually happening.
Dreams are a universal human experience and have always attracted the interest of man since ancient times. In the early twentieth century, dreams became a phenomenon worth of scientific study in Freud’s works; then, later on, since the mid-twentieth century they have become the subject of several empirical studies with sleep monitoring methodologies in sleep laboratories of North America, that gave rise to a spread of several neurobiological models based on the Rapid Eye Movement (REM) sleep = dreams equation. The most recent developments in brain imaging techniques and the study of dreaming in patients with brain lesions have allowed the scientific community to observe the active neuroanatomical regions underlying the dreaming processes. However, notwithstanding the continuing progress in dream science, certain key questions concerning the individual significance of dreams, their meaning in the context of human psychology, and their possible functions are still open to this date. After a short historical excursus and an outline of the developments in dream research, this paper describes certain current key questions faced by dream researchers, as well as the most influential theories on the possible functions of dreams.
The Chester Beatty papyri (1350 BCE) show that dreams are a phenomenon that has always fascinated and attracted the interest of human beings. In ancient times, dreams had an oracular and prophetic value. Through dreams, gods would guide men and affect several aspects of human lives by anticipating events (see Norman Mackenzie 1965). In ancient Greece, dreams also had a therapeutic function through the cult of incubation, where dreams induced in a temple could reveal a medical treatment. However, with Aristotle (fourth century BCE) and the atomists Leucippus and Democritus dreams started being studied as a natural inner phenomenon of man, and the first explanations of psychological and physiological nature were formulated. Later, Artemidorus (second century CE) tried to develop a first, systematic way of interpreting dreams that took into account the cultural, economic, and social context as well as the dreamer’s personality. In the early Middle Ages, there still was an inclination to believe in the oracular value of dreams. Furthermore, dreams and their interpretation (as it occurred among the Greeks) were seen as the privileged activities of few aristocrats (like emperors and kings). In the late Middle Ages (twelfth century), the dream phenomenon gradually lost its oracular value and started to be seen as a type of knowledge that was realized and expressed in metaphorical and symbolic forms. Dreams also started to gain consideration within the natural sciences. In addition, every man and woman could, by then, have a dream and interpret it (i.e., laicization and democratization of dreams). In the seventeenth and eighteenth centuries, the origin of dreams was attributed to man, and divine and supernatural causes were excluded. The influence of the Enlightenment and the fast progress of mechanics and physics led to the adoption of mechanistic models in physiology and to a reduction of the psychic fact to the nervous system activity. In this context, dreams were considered nonsense and an epiphenomenon of substantially somatic-physiologic mechanisms. During the nineteenth century, there was a spread of many theories on dreams that had opposing positions about the meaning and the function of dreaming. In the first half of the nineteenth century, the theories about dreaming were, to an extent, affected by the influence of Romantic philosophy. The dream was considered as the result of valid and important psychic activities with an inner meaning that could be deciphered and interpreted to reach a new understanding (e.g., G.H. Von Schubert; Hervey de Saint Denis). The second half of the nineteenth century saw the diffusion of medical and physiological theories about dreams. At that point, dreams were considered as an epiphenomenon of organic factors, a result of random and uncoordinated neurological activity, meaningless and uninterpretable (e.g., A. Maury; C. Binz). In the late nineteenth century and in the early decades of the twentieth century, more systematic studies on dreams started to spread (e.g., Calkins, M.W.; De Sanctis, S.; Kimmins, C.W.), the results of which, however, were deemed largely unproductive, due to numerous methodological limitations, by G. Ramsey, in 1953.
Freud’s Theory of Dreams
The distinctive aspect of Freud’s theory is the explanation of dreams in relation to a well-defined model of the human being’s general mental functioning. In Freud’s view, dreams are a motivated, meaningful, and sensible psychic act, although not immediately comprehensible. Dreams consent a disguised fulfillment of unconscious wishes (morally and/or ethically reprehensible) that, if expressed clearly, would endanger the dreamer’s mental health and the civil and social human existence. Wishes per se, with their pressing demand, provide the energy that triggers dreams. In other words, dreams act as a safety valve for dangerous individual instinctive energies, without interrupting the sleep (Freud 1900).
Modern Dream Research
The Discovery of REM Sleep
In 1953, Eugene Aserinsky and Natalie Kleitman, at the sleep laboratory of the Chicago University, discovered the sleep phase characterized by Rapid Eye Movements (REM) and its association to the dreaming experience. Later on, William C. Dement’s research (e.g., Dement & Kleitman, 1957), showing that subjects reported dreams upon awakening from REM stage and not from other stages of sleep, gave further strength to the assumption that REM = dreaming. In this climate, there was a huge growth of empirical research on dreaming based on the use of sleep lab methodologies, and there was hope that certain key questions about dreams would soon find an answer. However, one negative aspect of this scenario was that dreams had become a predominantly electrophysiological phenomenon, explained merely by the cortical activation of REM sleep.
Freud’s Theory of Dreams in Sleep Laboratories
However, in the early years of dream studies conducted at sleep laboratories (1960s), there were also several attempts to merge Freudian concepts with the data from psycho-physiological research on REM sleep and dreaming. Nevertheless, those studies frequently failed to reach clear results regarding the psychoanalytic assumptions they tried to verify, due to the lack of an appropriate background of knowledge about Freud’s dream theory, so that the assumptions they formulated did not represent a correct evaluation of the original Freudian hypotheses.
The Decline of Freud’s Dream Model and the Diffusion of Neurobiological Approaches
The REM sleep = dream equation had two apparently important implications for Freud’s dream model: (a) The cyclical and automatic character of REM sleep and dreams led to considering dreams as events caused by neuro-physiological factors rather than by affective–motivational instigation. (b) Studies on test animals showed that REM sleep is activated by brainstem structures and that the forebrain (i.e., the ideational and cognitive center) does not need to be active in order to trigger the REM sleep phase, and hence dreaming. Both results apparently clash with the Freudian hypothesis of dreams as valid psychological phenomena with ideational-motivational meaning. In this climate, various neurobiological theories on dreams developed. According to the most popular one, the “activation-synthesis” theory, dreams are simply the by-product of neurobiological events during REM sleep state and are therefore inherently meaningless and do not require any interpretation (Hobson and McCarley 1977).
The Cognitive Approach to Dreaming
Cognitive dream models also focus very little on dream contents and meaning and on dream interpretation, privileging the study of dream production processes (e.g., see models of John Antrobus and of David Foulkes). However, unlike in most neurobiological models, in cognitive studies (with the important contribution of the Department of Psychology at the University of Bologna, Italy) the hypothesis that dreaming is distributed along all sleep stages has made its way. These studies showed that a high percentage of subjects who awakened during NREM sleep could recall their dreams (much also depends on the definition of dream being used) and that NREM dreams are similar to REM dreams under various aspects (e.g., Foulkes 1962; Cicogna et al. 2000). The assumption from this perspective is that the underlying cognitive processes of dream production may be the same through all sleep stages, although with different levels of engagement associated with different levels of brain activation (i.e., the so-called “single dream generator” theory).
The Brain Lesion Studies
In the course of time, further major empirical evidence has shown that REM sleep is a condition neither necessary nor sufficient for the dream experience. Brain lesion studies (i.e., the studies of the impact on dreaming of a trauma suffered by a given brain area) (Solms 1997) have suggested that: (a) dreaming is preserved even when a major damage to pontine brainstem removes REM sleep and (b) the neuroanatomic bases that seem to be most involved in the dream production process are those that “affective neuroscience” (e.g., Panksepp, 1998) has identified as involved in the instigation of goal-seeking behaviors and appetitive interactions with the world (i.e., the mesocortical dopaminergic system).
Freud’s Theory of Dreams Revaluated
Starting from the first half of the 1990s, several studies have prepared the ground for a reconsideration of Freud’s dream theory: (1) the reprise, in cognitive psychology, of certain Freudian mental constructions (e.g., the unconscious) (e.g., Erdelyi 1985); (2) the use of functional neuroimaging techniques (PET – Positron Emission Tomography and fMRI – functional Magnetic Resonance Imaging) that facilitated the study of the neuroanatomic bases of emotions and of primary motivations (“affective neuroscience”) (e.g., Panksepp, 1998), as well as the involvement of emotional and motivational brain (i.e., several forebrain structures, including frontal and limbic areas) in the dreaming processes (e.g., Maquet et al. 1996; Braun et al. 1997); and (3) the above-referred brain lesions studies according to which dreams are instigated by “appetitive drives” (associated with terms like “curiosity” or “interest”) which is consistent with Freud’s idea that dreams are instigated by wishes and give expression to instinctual drives (i.e., the hypothesis of motivational instigation of dream).
Some Current Key Questions in Dream Research and Theory
The Nature of “Dream Bizarreness”
The problem of the origin of “dream bizarreness” (i.e., the impossible and/or improbable characteristic of dreams) has become crucial in the current dream research debate (Colace, 2012). While neurobiological approaches ascribed dream bizarreness to the unique neurobiological conditions of the brain during REM sleep (temporally random and noncognitive input from the brainstem, and the aminergic demodulated forebrain’s attempt to give sense to this random bombardment), and consider bizarreness as a default property of all dreams, avoiding all psychological significance and interpretation intents, Freud’s disguise-censorship model describes dream bizarreness as the expression and the result of a motivated effort to disguise unconscious wishes that are morally and ethically unacceptable to the dreamer’s conscience. Recent studies have shown unequivocally that most young children’s dreams are frequently simple and understandably related to everyday experience without any sign of bizarreness in their content (Colace 2010). This might prove that dream bizarreness cannot be considered as intrinsic to the nature of dreaming processes nor a universal property of dreams.
Sleep, Dream, and Emotional Regulation
The most influential theories on the function of dreams
Emotional adaptive theories
Dream serves to discharge instinctual energies (i.e., safety valve for the psyche)
Dream preserves sleep by treating the stimuli that disturb it
Breger, Hunter and Lane2; Fiss3, Cartwright4
Dream resolves emotionally disturbing events
Dream serves a biological and adaptive function by simulating threatening events and improves the dreamer’s ability to cope with threats during the state of wake
Dream has a role in reinforcing the typical behavior of a species. Dream could be involved in the stability of the dreamer’s personality (Psychological individualism)
Dream reduces the intensity of emotional distress or calms emotional storms
Dream serves as mood regulator
Nielsen and Levin9
Levin and Nielsen10
Dream serves to facilitate fear memory extinction through the recombination and finally the expression of the associated emotions, allowing a downregulation of negative and arousing emotions
Dream serves as regulator and restorer of psychological organization and affectivity
Dream resolves a unprocessed and disturbing affective state and provides an affective reestablishment of the dreamer
Perogamvros and Schwartz13
Dream may have a role in learning and memory, as well as in emotion regulation processes (Reward Activation Model)
Crick and Mitchison14
Dream serves to reduce memory-redundant associations or parasitic thoughts during REM sleep
Dream may contribute to the formation of new ideas. These may be selected and developed if useful, or discarded if useless or maladaptive (theory of “Oneiric Darwinism”)
Wamsley et al.16
Dreams may improved spatial memory performance
No function theories
McCarley and Hobson17; Hobson18
Dreaming is a by-product or random result of a REM physiological state; it has no motivational function. Cognitive content is ambiguous and misleading (“Activation-sytnhesis hypothesis”; AIM model)
Dreaming is instigated by random diffuse mnestic activation (i.e., not psychologically motivated). It has no special purpose nor deep meaning and nor adactive functions. However dreams are a high-level cognitive process that reveal conceptual and personal knowledge of dreamer
Hobson and Friston20
Dreams providing a virtual model of the world would be necessary for the development and maintenance of waking consciousness. Dreams are a mere subjective epiphenomena of REM sleep (i.e., sleep-dream protoconsciousness theory
The Theoretical-Epistemological Debate on Freud’s Dream Theory
Recently, J.A. Hobson reiterated the hypothesis (inspired by Karl Raimund Popper, 1959) of the alleged empirical untestability (for lack of scientific standards) and scientific obsolescence of Freud’s dream theory. Actually, contrary to Popper’s and Hobson’s positions, clear examples of empirical falsifiability have been provided for some Freudian clinical hypothesis (Grünbaum, 1984) and also for several assumptions in Freud’s theory of dreams (Colace 2010), revealing their scientific vitality and usefulness in explaining the dream phenomenon in various fields of application (Colace and Boag 2015; Michael 2015).
What Are the Functions of Dreams?
Theories about the possible funtions of dreams included an attempt to answer to such key questions on dreaming as: Are dreams a valid mental act? Do dreams have a meaning? Most influential theories are summarized in the Table 1 below.
Conclusions. Dreams: Motivated Phenomena or Meaningless?
The studies suggesting a motivational instigation of dreams, and the data on the role of sleep and dream in the re-activation and processing of recent significant emotions and experiences, appear to support an interpretation of dreaming as a significant psychological and motivated event, rather than as the result of a random process or a by-product of the physiological state of sleep.
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