Dreams have always been an object of fascination for people. It is very likely that dreams helped to shape human consciousness from the dawn of humanity. When Neanderthals and anatomically modern humans began to bury their dead some 200,000 years ago and when they began to decorate those burials with red ochre and other materials these peoples witnessed to a belief in a spirit world, most directly experienced in dreams, where the dreamer’s spirit wandered around and communed with the spirits of the animals and occasionally met spirits of their dead loved ones. Even today people who have lost a loved one very often experience the appearance of that loved one in dreams as confirmation that the loved one still lives somehow in the spirit world. For early peoples therefore the dream was the portal to the spirit world. The first systematic explorers of the dream world were therefore very likely spiritual specialist or shamans and healers. When the shamans took their initiates deep into the caves of Lascaux or Chauvet they very likely took them to view the animals that populated the spirit world—as derived from dreams. The images on the cave walls painted some 30,000 years ago in Europe may have had their source in dreams.
The act of exteriorizing one’s dream images by painting them on a cave surface was a genuine breakthrough in understanding dream imagery. Dreams were valorized as genuine manifestation of the gods and spirit world. If we use the method of examining modern ethnographic parallels to ascertain how people might have worked with dreams for the tens of thousands of years before the onset of the Neolithic, agricultural age we see that these people gave dreams a place of honor in their cultures. Lohmann (2007) has provided a recent survey of the literature on dreams in pre-modern cultures. In general, these people distinguished between several types of dreams. Some dreams were considered as the products of the imagination and therefore useful for entertainment in the form of story-telling. Most pre-modern peoples, however, regarded most dreams as arenas for interaction with the spirit world. Thus, Michael Harner (1972) reports that the South American Jívaro consider dreams to reveal a more true spiritual reality behind the illusory images people perceive in waking life. The Zuni and Quiché Maya traditions studied by Barbara Tedlock (1987), for example, see dream images as communications from ancestors, spirits, or divinities. The Tikopia (Firth, 2001) in Polynesia see dreams as opportunities for visitation of spirits to the dreamer. Perhaps most commonly among pre-modern peoples, dream images are explained as the experiences and perceptions of the dreamer’s soul, as it wanders outside the body (e.g., Gregor, 1981a, 1981b on Amazonia; Lohmann, 2003a, 2003b on Oceania; and Tonkinson, 1974, on Aboriginal Australia).
Given what we know concerning the centrality of group dream sharing in pre-modern tribal groups (Gregor, 1981a, 1981b, 2001; Schneider & Sharp, 1969; Tedlock, 1992a, 1992b), we can assume that dream sharing was a common practice in early human groups.
Even today young adults recall one to two dreams per week with 37% of these reporting that they recall a dream ‘every night’ or ‘very frequently’ (K. Belicki & D. Belicki, 1986; Goodenough, 1991; Strauch & Meir, 1996). In representative samples of the general population, between 40 and 75% recall between one and five intense and ‘impactful’ dreams per month (Borbély, 1984; Kuiken &d Sikora, 1993; Stepansky et al., 1998). Once recalled a dream is typically shared with another person (Stefanikis, 1995; Vann & Alperstein, 2000). For example, Vann and Alperstein reported that 98% of the 241 individuals they interviewed reported telling dreams to others, particularly friends and intimates. Once shared, they have the potential to go on influencing daytime mood and behavior of both self and others.
With the waning of the hunter gather way of life and the onset of the Neolithic dream sharing and dream exploration picked up speed. Dreams were still considered portals to the spirit world so the dream explorers were still generally the religious specialists. The bronze age and the classical age brought the first stirring of rational investigation into dreams but this work resulted in only in huge compendia of dream examples and their preferred interpretations. In the west the Greeks began to ask about the nature for the dream while in the east the Hindu and Buddhist religious specialist began to use lucid dreaming practices to explore the dream realm.
With the close of the axial age of world civilizations the west during the mediaeval period and the Islamic world entered a period of far reaching philosophical investigations grounded in recovery of the Greek philosophical classics. Here however no new empirical information was added to the database on dreams. With the onset of the enlightenment however some 4 centuries later dream research really began to take off. Yet again however this research was not empirically driven. Instead the dream was used in thought experiments to buttress skeptical portraits of man’s ability to know the waking world with any kind of epistemological certainty.
Empirical research on dreams had to await the dawn of the 20th century. It was the indeed the dawn of the 20th century that saw the publication of Freud’s ‘Interpretation of dreams.” Freud’s work was definitely a landmark publication on dreams but it was tied to a rather narrow evidential database and a rather elaborate theory of the psyche. Carl Jung’s work on dreams began with Freud’s hypothesis that dream content was the source of mythic (e.g. Oedipus) imagery and stories but soon discarded the Freudian theoretical apparatus. Jung presented a range of clinical and textual evidence for the view that dreams contained mythic archetypal universals that reflected psychic contents appropriate to universal conditions of humankind. But again the evidential database for these extravagant claims often outran the theoretical speculations Jung offered in his books and thus the speculations could not be sustained. Jung died in 1961. The epoch making discovery in dream research was made in 1953 but Jung and the depth psychology community in general seemed not to register the event at all.
The modern period in dream research was initiated by the epoch making discovery of REM sleep by Aserinsky and Kleitman in 1953. Our most vivid dreams occur in REM sleep and thus a biology of dreaming became possible. Since 1953 literally thousands of studies have been conducted on REM dreams by awakening people when they exhibit the EEG and behavioral signs of rapid eye movement sleep. Thousands of content studies of these dreams reveal some stable characteristics of REM dreams: they are typically vivid visual simulations of social interactions involving a mix of familiar and unfamiliar characters and often involving bizarre situations or events. No current theory of dreams can explain the peculiar content of REM dreams. That content is not consistent with Freudian or Jungian theory. Nor is it consistent with any other current theoretical accounts of the dream.
The activation-synthesis theory originally described by Hobson and McCarley (1977) and updated recently by Hobson et al. (2000b) as the activation-input source-neuromodulation model or AIM model of dreaming, represents some of the finest work accomplished in the study of sleep and dreams. In the AIM model REM sleep generation is conceived as a process involving every level of the neuraxis, from the brain stem to the reticular activating system in the midbrain, to the hypothalamus and thalamus, basal forebrain, amygdala, limbic system, and cortex. Cortical activation (A in AIM), in addition to brain stem activation, is given great weight in the new model. Cortical activation allows for efficient access to significant amounts of stored information during dream synthesis. Dream construction depends on access to an internal (I) source of information, which is facilitated (or forced) by sensory blockade during REM. The shift of the brain from aminergic to cholinergic neuromodulation (M) reduces reliability of cortical circuits in dream construction, thus increasing the likelihood that dreams will contain bizarre elements.
Antrobus (1987, 1991) attempted to provide a neurocognitive model of dreaming. In his neural network simulations of dreaming, Antrobus assumed that the properties of both dream and waking mentation varied as a function of cortical activation and degree of external stimulation (indexed by sensory thresholds). What created the dream narrative was not so much the brain states NREM or REM but rather intracortical interactions of specialized cortical networks mediating relevant sensorimotor and cognitive functions along with incoming subcortical inputs that needed to be integrated into ongoing cortical processing. Dream bizarreness, in this model, is due to failure to adequately summate all of these competing inputs to ongoing dream construction.
Solms (1997, 2000) has systematically investigated the effects of brain lesions on dream expression. He submitted a questionnaire on recall of dreams to 332 patients with various types of cerebral lesions (and 29 nonlesioned controls). Reports of global cessation of dreaming were associated with lesions in the region of the inferior parietal lobes on either side or with lesions deep to the medial frontal region in the white matter tracts connecting the frontal lobes with both cortical and subcortical sites. Two hundred patients with lesions outside these areas reported no changes in their dreaming patterns. This set of lesions would presumably disconnect anterior frontal cortex from subcortical and limbic sites. Thus, the mesofrontal tracts likely play a role in the generation of dreaming. Many of these tracts are catecholaminergic, and Solms believes that the most important ones for dreaming are the dopaminergic tracts that predict reward-related incentives (the appetitive and expectancy circuits). Thus Solms argues that these data support some of Freud’s speculations regarding the wish fulfillment functions of dreams.
Domhoff (2003) draws on Solms’s data, the recent set of findings gathered from neuroimaging studies, and his own extensive studies on dream content to propose a detailed neurocognitive model of dreaming. Like Hobson et al., Antrobus, and Solms, Domhoff suggests that dreaming depends on brain activation patterns, but the content of dreaming comes from access to the conceptual system of schemata and scripts housed in the cognitive system. This attention to cognitive detail and modern cognitive science theory is a real advance over previous neurocognitive models.
Revonsuo (2000) proposes that the function of dreaming is to simulate threatening events. Threat simulations are thought to allow for rehearsal of threat perception and thus to enhance threat avoidance. Revonsuo notes that dream content is not random but instead consistently over represents simulations of unpleasant or threatening events. In some cases, these simulations are repetitions of previous unpleasant dreams (Domhoff’s repetition principle) such as a nightmare of being chased by a wild animal, and so on. Repeated simulations of such threatening events in the dreaming mind of an ancestral human are thought to confer a selective advantage on that individual relative to individuals not experiencing such simulations. The advantage might be a slightly faster response time when confronted with a threat or a slightly improved ability to detect an incipient attack, and so forth. Children, in particular, would benefit from such a threat simulation device, and studies of dreams of modern children show that wild threatening animals are over represented in their dreams.
McNamara (2004; McNamara et al., 2010) presented an extensive amount of data on content differences between REM and NREM dreams and he argued that any adequate account of dreams must explain these content differences. He argued that REM and NREM sleep mentation differences expressed internal psyhic conflict grounded in genomic conflict.
Scherdl (2000x) has presented an abundance of empirical data on all kinds of content indices of dreams. He argues that most dreams are not that different from waking consciousness and that they reflect current concerns of the individual dreamer. This is known as the continuity hypothesis.
While the above mentioned theories are the most debated in current dream research none of them have proved adequate to the protean phenomena of dreams themselves and so the field is still awaiting a theoretical breakthrough.
Patrick McNamara, PhD
Chief Scientific Advisor, Dreamboard Inc.