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A New Neurocognitive Theory of Dreams:
Ideas and Findings that Support a Potential Synthesis
in the Study of Dreams

G. William Domhoff
Psychology Department
University of California
Santa Cruz, CA 95064
(831) 429-1446
domhoff@cats.ucsc.edu

Abstract

Discoveries in three distinct areas of dream research make it possible to suggest the outlines of a new neurocognitive theory of dreaming that relates to a general theory of thinking, including the question of consciousness and how it develops. The first relevant findings come from work in the sleep laboratory, including longitudinal and cross-sectional developmental studies which reveal that only 20-30% of REM period awakenings lead to dream reports up to age 9, that the dreams of children under age 5 are bland and static in content, and that children cannot regularly include themselves as an active character in their dreams until about age 8. The second set of results comes from assessments of patients with brain lesions, which show that those who suffer insults to either parietal lobe or sustain bifrontal white matter injuries report loss of dreaming even though they continue to have REM sleep; that lesions in the visual association cortex lead to loss of visual dreaming; that injuries to the frontal-limbic area lead to increased frequency of dreaming and confusion of dreaming and reality; and that lesions to the temporal-limbic area lead to repetitive frightening dreams. The third set of findings comes from a rigorous system of content analysis, which demonstrates that the dreams of college students have not changed over the past 50 years, that dreams do not change with age after young adulthood, that dreams are more similar than different all over the world, that the dreams of individuals who keep dream journals are remarkably consistent over years and decades, and that dream content is in general continuous with waking conceptions and emotional preoccupations. Based on these findings, dreaming is a developmental cognitive achievement that depends upon the maturation and maintenance of a specific network of brain structures, and the output of this system is determined by a 'continuity principle' linked to current emotional concerns on the one hand and a ìrepetition principleî rooted in past emotional preoccupations on the other. The net result is a neurocognitive theory of dreams that contradicts the claims of Freud and other clinical theorists on the one hand and Hobson and other theorists who in effect equate REM sleep and dreaming on the other.

Introduction

Theorizing about dreams in the twentieth century was dominated by the clinically based theories developed by Freud and his opponents on the one side and the neurophysiological theories based on the equation of REM sleep and dreaming on the other. Neither type of theorizing holds out much appeal to those who work in the cognitive sciences. The clinical theories are suspect because they are based on retrospective dream analyses of an anecdotal nature that cannot be verified. In addition, they emerge from a context in which respect for authority, cognitive dissonance, and the demand characteristics of the situation may lead to the acceptance of implicit suggestions made by the clinician.(Loftus & Ketcham, 1994; Ofshe & Watters, 1994). Indeed, there is now experimental evidence that many participants in simulated clinical interviews concerning their dreams can be convinced that suggested events did happen to them before age 3. (Mazzoni & Loftus, 1998; Mazzoni, Loftus, Seitz, & Lynn, 1999).

REM-based theories stressing the bizarre and chaotic character of dream content imply there is little of use in sleep for those who study waking cognition.(Crick & Mitchison, 1983; 1986; Hobson, 1988; Hobson & McCarley, 1977). Those theories are called into question by the fact that there are full-blown dreams outside of REM periods, especially late in the sleep period; that there can be REM sleep without dreaming in young children, luekotomized schizophrenics, and brain-injured patients with parietal or bifrontal white matter damage; and that there are no correlations between phasic neurological events in REM sleep and changes in dream content. (Antrobus, 1983; Foulkes, 1982; 1985; Herman, Ellman, & Roffwarg, 1978; Solms, 1997; 2000; Vogel, 1978). The general results from dream content analysis also raise doubts about this theory. (Domhoff, 1999a).

Due to the failure of the clinical and REM theories to produce any evidence for the lawfulness of dreaming as a cognitive process, it comes as no surprise that few or no cognitive scientists have any interest in trying to incorporate dreaming into their theories. However, it may come as a surprise to cognitive scientists that some of the same factors that led to the rise of cognitive science also have generated findings about dreaming and dream content that actually hold out great potential value for new theoretical developments. These descriptive empirical results suggest that dreaming has many parallels with waking thought, and may even be of use in trying to come to grips with the development of consciousness. These findings come from three sources: the sleep laboratory, including two large-scale developmental studies of dreaming; neuropsychological studies of the complete loss of dreaming or dramatic changes in dreaming in patients suffering from brain lesions; and a wide range of studies of dream content using the Hall and Van de Castle (1966) coding system to quantify many thousands of dream reports from people of all ages in many different parts of the world.

The main finding and insights arising from these very different types of studies are presented in the next three sections, along with their implications for a neurocognitive theory of dreams. The fourth section suggests ways in which these diverse findings can be linked to each other and synthesized into a new neurocognitive theory of dreams. The burden of the paper, as expressed in a concluding section, is that the time may be ripe for a new approach to dreams despite the remarkable persistence of traditional dream theories in the face of contradictory evidence.

Dreaming and Cognition in the Sleep Laboratory

The serendipitous discovery of sleep stages in 1953, and especially the finding that the four or five Rapid Eye Movement (REM) periods of the night lead to dream reports from 80-90% of awakenings in most normal teenagers and adults, led to an enormous advance in the understanding of both sleep and dreaming. (Dement & Kleitman, 1957a; 1957b; Foulkes, 1966; Kamiya, 1961). These studies demonstrate that dreaming is far more ubiquitous in both REM and non-REM (NREM) sleep than any previous dream theorist had ever imagined, that it cannot be triggered by external stimuli, and that dream content is by and large impervious to the wide range of presleep and concurrent stimuli that have been used in an attempt to influence it.(Foulkes, 1985; 1996a). They further show that dreams collected from awakenings in the sleep laboratory, whether from REM or NREM sleep, are in large measure coherent and reasonable simulations of the real world, which suggests there is a greater parallel between dreams and waking thought than is assumed by either clinical or REM dream theorists (Cavallero & Foulkes, 1993; Foulkes, 1985; Meier, 1993; Snyder, 1970; Strauch & Meier, 1996). Moreover, specific dreaming deficits, such as loss of visual dreaming, correlate with similar waking cognitive deficits, which suggests there are common neuropsychological processes involved as well (Kerr, 1993; Kerr & Foulkes, 1981; Kerr, Foulkes, & Jurkovic, 1978; Solms, 1997; 2000).

In addition, there are several studies suggesting that waking thought can have dreamlike qualities, especially when relaxing in a darkened room. In the first two of these studies, awake participants monitored by the EEG while resting quietly in a dimly lighted room gave dreamlike responses to 15-20% of the requests for reports of what was going through their minds (Foulkes & Fleisher, 1975; Foulkes & Scott, 1973). In another set of laboratory studies, judges who compared REM reports with thought reports from awake participants reclining in a darkened room rated the waking reports as more dreamlike (Reinsel, Antrobus, & Wollman, 1992; Reinsel, Wollman, & Antrobus, 1986). Finally, a field study of waking consciousness--using pagers to contact participants-- discovered that 9% of the 1,425 thought samples had ìmore than a traceî of dreamlike thought and another 16% had a ìtraceî of such thought (Klinger & Cox, 1987/1988). Taken together, these studies lead to the idea that dreaming is not necessarily a function of sleep, thereby providing another possible linkage between waking cognition and dreaming. Instead, dreaming simply may require a high level of brain activation along with a reduction in external stimulation and a decrease in self-control (Antrobus, 1991; Foulkes, 1999).

It is within the context of this general evidence for the overlap of waking cognition and dreaming that two-large scale studies of the development of dreaming in children, one longitudinal, one cross-sectional, provide the first systematic basis for a neurocognitive theory of dreaming (Foulkes, 1982; Foulkes, 1999; Foulkes, Hollifield, Sullivan, Bradley, & Terry, 1990). The longitudinal study began with 7 boys and 7 girls ages 3-5 to cover the ages 3-9 over the five-year span of the study. It also included 8 girls and 8 boys ages 9-11 to account for the years between 9 and 15. Remarkably, all of the 14 children in the younger group participated in all five years of the study. Twelve of the 16 in the older group completed the study; the other 4 moved out of town.

To check on the possibility that participation in the study improved dream recall and accounted for any increases in the frequency and narrative complexity of dream reports, 6 boys ages 11-13 were added to the older group in the third year and 7 girls ages 7-9 were added to the younger group in the fifth year, with the finding that the new participants generally did not differ on any dream measures from the original participants. In total, 26 children between the ages of 3 and 15 participated for five full years, 34 for at least three years, and 43 for at least one complete year. Normative dream data for each group were collected during the first, third, and fifth years of the study, when children slept in the laboratory for 9 nights each. They responded to 3 awakenings a night from either REM or NREM sleep for a total of 2711 awakenings. All the awakenings were carried out by Foulkes to insure experimenter consistency. During the second and fourth years the children participated in a variety of methodological studies, the most important of which compared dreams collected after a night of uninterrupted sleep in the laboratory with dreams collected in the morning at home by parents.

In addition to information on the frequency of dream recall and the content of the dream reports, a wide range of personality and cognitive tests were administered by other members of the project team, information about school performance was obtained, and observations of the youngest group were made at a two-week nursery school during the first three summers of the study. A total of 657 non-dream variables was correlated with the dream data because ìit would have constituted criminal neglect to have collected so many dream data and not to have searched far and wide for waking variables related to them(Foulkes, 1999, p. 49).

The cross-sectional study focused on children ages 5-8 to see if the most interesting results of the longitudinal study could be replicated. It included 20 children at each age who were within one month of their birthday for a total of 80 children who spent 3 nights in the sleep laboratory. They were each awakened a total of 10 times, with all of the 800 awakenings once again carried out by Foulkes. The children also took several cognitive tests measuring visuospatial, verbal, descriptive, and memory abilities that had correlated with dream recall or length of dream reports in the first study. In neither study did Foulkes know the results of the daytime tests until he had collected all of the dream data.

Findings on Dream Recall and Dream Content

There are several replicated results from these two studies that are important for a neurocognitive theory of dreams. None of the findings on rate of recall, report length, or narrative complexity showed any gender differences. First, and most unexpected, the median rate of dream recall was only 20-30% from REM awakenings until ages 9-11, when the median recall rate of 79% from REM awakenings approached adult levels. Recall from NREM awakenings went from 6% at ages 5-7 to 39% at ages 11-13. For both REM and NREM awakenings, recall came first from awakenings late in the night, then from awakenings in the middle of the night, and finally from awakenings early in the sleep period.

Second, the children's dream reports had very different content until ages 13-15 than what is reported by adults. For children under age 5, the REM reports consisted primarily of static and bland images in which they saw an animal, or were thinking about eating or sleeping. The dreams of children ages 5-8 showed a sequence of events in which characters moved about and interacted, but the dream narratives were not very well developed. Even more striking, it was not until age 8 that the dreams regularly included the dreamer as a participating character, which Foulkes sees as a fact with major implications for the study of consciousness. Compared to the dream reports of adults, those of the young children were notable for their low levels of aggressions, misfortunes, and negative emotions (Domhoff, 1996; Foulkes, 1982; 1999). Gender differences in dream content did begin to appear in late childhood (Domhoff, 1996; Foulkes, 1982), but were more prevalent by adolescence (Trupin, 1976).

The results on both recall and content are of great theoretical importance because they suggest that young children do not dream in the fashion expected by either the clinical or REM theorists. Instead, they reveal dreaming to be a cognitive achievement which develops gradually in the same way that many other cognitive abilities develop in children. The frequency and cognitive structure of children's dreams is not adult-like until ages 9-11, and the dream reports are not adult-like in length or content until ages 11-13. Although Freud (1900) and his co-workers claim that the dreams of preschool children--either overheard in the form of sleeptalking or reported to parents upon awakening-- are excellent evidence for the Freudian theory that all dreams contain a wish fulfillment, there is little or no sign of wishes in the cognitively impoverished dream reports collected by Foulkes. It therefore seems likely that the overheard ìdreamsî are the products of sleeptalking during one of the many micro-awakenings of 10 to 20 seconds that children and adults alike experience each night (Arkin, 1981; Boselli, Parrino, Smerieri, & Terzano, 1998; Mathur & Douglas, 1995). Nor is the static and bland content in these dreams anticipated by Jungian theory, which claims on the basis of adult recall of childhood dreams that the dreams of young children are more likely than ordinary adult dreams to be highly symbolic products of the collective unconscious (Jung, 1974; Kluger, 1975; Mattoon, 1978).

For the REM theorists, the absence of dreaming from so many REM periods is clearly a major surprise because of their continuing effort to place ìrealî dreaming within REM sleep or 'covert' REM sleep (Hobson, Pace-Schott, & Stickgold, 2000; Nielsen, 2000). The fact of significant NREM reporting by ages 11-13, especially from Stage II NREM late in the sleep period, also contradicts their expectations. To deal with the low recall from REM periods, they could have modified their view to say that REM sleep is necessary but not sufficient, but instead Resnick, Stickgold, Rittenhouse, and Hobson (1994) argue that the children in Foulkesí studies felt uncomfortable and inhibited in the laboratory. They then present their own evidence of full-fledged dreams from preschool children on the basis of home-reported dreams collected by parents after having the children repeatedly tell themselves at bedtime that they will remember a dream in the morning.

Contrary to their claims, Foulkes (1982; 1999) presents detailed evidence that his extensive efforts to make the children comfortable in the laboratory setting did prove successful. In addition, and again contrary to the claims by Resnick, Stickgold, Rittenhouse, and Hobson (1994), he tested for the possible effects of awakenings during the second and fourth years by allowing the children to sleep throughout the night in the laboratory and then report any dreams they recalled in the morning. This procedure showed there were no differences with dreams collected after morning awakenings at home, which means any differences between dreams collected from awakenings in the laboratory and at home are due to selective recall for atypical dreams at home rather than to any alleged inhibitory effect in the laboratory (Foulkes, 1979; 1982; 1996b). Foulkes (1996b; 1999) also notes that the implicit pressures to recall dreams in the Resnick, Stickgold, Rittenhouse, and Hobson (1994) study might have led to made-up dream reports on the part of the children. Since many pre-school children seem to have an understanding of what dreaming is (Woolley, 1995), despite the paucity of their own dream lives, there is now a need for new research on the way in which childrenís ìtheory of mindî interacts with what they learn about dreams from their parents and books to produce their beliefs and reports-- about dreams.

Waking Correlates of Dreaming and Dream Content

There has been no rush to draw out the implications of this finding. Instead, skeptics argue that the low rates of recall in young children may be due to an inability to report the dream experience rather than a lack of dreaming. For example, Hunt (1989) thinks the problem may be an inability to distinguish the ìembeddedî experience of a dream from other subjective states; others say that children simply may lack the linguistic skills to translate the non-verbal experience of dreaming into the narrative report necessary to show evidence of dreaming (Hobson et al., 2000; Weinstein, Schwartz, & Arkin, 1991). Foulkes finds these alternative explanations unlikely because none of the several linguistic, descriptive, memory, and story telling tests administered to the children correlated with rates of recall. Such explanations are also contradicted by the fact that both REM and NREM reports are first given late in the sleep period; it does not seem likely that either discriminatory or narrative skills would be unavailable earlier in the night once they had developed.

The idea that young children do not dream very well until their visuospatial skills are developed is supported by Foulkes' findings with two of the boys ages 11-13 ages who were added to the study during its third year. Both of them had average memory and verbal skills, and both were adequate students in school, but both turned out be very low on visuospatial skills. Neither reported very many dreams during REM awakenings, far below the average for all other children in their age group. Since neither of these boys lacked the linguistic skills claimed by critics to be the reason why younger children do not report dreams when awakened in the laboratory, it seems far more likely that they were not dreaming when awakened during REM sleep.

The importance of visuospatial skills for dreaming also has been demonstrated in a study of adults who claim they seldom or never dream The original pool of possible participants for this study was found through a newspaper ad asking for men who 'rarely or never dream' (Butler & Watson, 1985, p. 824). They were screened by means of a ten-day dream diary to eliminate those who wrote down dreams on four or more mornings. Six low recallers with high scores on the Block Design test and six low recallers with low scores on Block Design were then awakened in the laboratory during every REM period over two nights for a total of 106 awakenings. Recall percent was 83.5% for low recallers with high Block Design test scores, but only 48.5% for those with low scores; unexpectedly, there was a large variation from 0% to 100% recall among the six with low Block Design scores. However, those with low recall in the laboratory generally scored low on visualization tests other than Block Design, suggesting that a more general visuospatial dimension is involved in their failure to report dreams. Since those with low visuospatial scores had normal verbal and general intelligence, it seems likely that those who did not report dreams were not dreaming. These findings support Foulkes on the importance of visuospatial skills for dreaming in children, although they also show that a systematic research program would be needed to sort out the various reasons for non-reporting of dreams.

Returning to Foulkes' longitudinal study, the rarity of non-dreamers by late childhood is shown by the fact that visuospatial skills no longer correlated with rate of dream recall by ages 9-11. By that age the great majority of the children were able to dream proficiently, as indexed by higher rates of recall, more complex dream plots, and the ability to include themselves consistently as a character in their dreams. For most older children and adults, Foulkes (1999) argues, recall seems to relate to a wide range of variables. This conclusion is consistent with the fact that the search for cognitive and personality correlates of recall in large samples of representative adults has led to small and inconsistent findings that cannot be replicated (Cohen, 1979; Goodenough, 1991; Tonay, 1993). In particular, and contrary to Freudian claims, there is no evidence that ìrepressionî or any other form of denial or self-deception correlates with lack of recall (Cohen, 1979; Goodenough, 1991).

Once children have the ability to dream, their linguistic and descriptive skills begin to correlate with the length and narrative complexity of their dream reports, which shows that these factors do contribute to dreaming, although not quite in the way that most dream theorists probably expected. Still, it is not until ages 11-13 that dream content shows any relationship to personality dimensions. For example, individualistic and assertive children portray themselves as more active in their dreams, children with more violence in their waking fantasies have more aggressive interactions in their dreams, and those who display the most hostility before going to bed in the laboratory more often dream of themselves as angry. These findings on the continuity of dream content and waking mentation support findings in earlier studies of children in the laboratory (Foulkes, 1967; Foulkes, Larson, Swanson, & Rardin, 1969; Foulkes, Pivik, Steadman, Spear, & Symonds, 1967). They suggest that dreams can reflect personality dimensions once there is an adequate level of cognitive development. In effect, this finding is what remains of the large claims by clinical dream theorists (Domhoff, 1999a).

Implications for Cognition and Consciousness

On the basis of the many cognitive correlates of dreaming in young children, and the lack of any correlations with personality measures until preadolescence, Foulkes (1985; 1999) presents a cognitive theory of dreaming that rejects the claims of both the clinical and REM theorists. His theory suggests that waking cognitive development and the development of dreaming are closely related, and that dreaming is based on the same conceptions that form the basis for thinking in waking life. He also draws on work with brain-lesioned patients to argue that his theory has links to neuropsychology as well (Foulkes, 1985; 1999; Kerr & Foulkes, 1981; Kerr et al., 1978). This neuropsychological dimension contradicts the claim by Hobson, Pace-Schott, and Stickgold that Foulkes' theorizing ignores possible neurological correlates of dreaming, although it is true that he rejects the attempt to find specific relationships between events in REM sleep and dream content (Foulkes, 1996a; 1999).

Moreover, (Foulkes, 1990; 1999) claims that developmental dream studies may provide a new avenue to the study of consciousness: dreaming is the form that consciousness takes during sleep. It then follows that the development of consciousness can be discovered by doing detailed studies of the development of the ability to dream. As one part of this general idea, Foulkes further suggests that the ability to include oneself in a dream, which is not fully developed until around age 8, with the usual allowances for individual differences, may be the best index there is of when a child has a full sense of self. He reached this conclusion after finding that three waking tests designed to assess the development of the ìselfî concept did not correlate with each other and did not predict the inclusion of the dreamer as a character in his or her dream reports: I believe that an index of REM dream self-representation is inherently superior to any waking measure of self phenomena currently available, or likely to be developed soonÖWhen we have replicated and reliable evidence, from this best of all avenues to children's mental experience, suggesting a startlingly different picture of the early development of human mental life, that evidence deserves our serious attention. The evidence I refer to, of course, indicates the surprising lateness in children's development of the ability to imagine themselves as actors in their own mental imagery (Foulkes, 1999, p. 95).

In attempting to build on Foulkes' cognitive theory of dreaming, it may be useful to turn to new ideas and findings that have been developed on the basis of neuropsychological research. In particular, the correlation Foulkes discovered between visuospatial skills and dreaming in children up to age 8 may be of special importance in this regard because visuospatial skills have been linked by neuropsychological studies to specific locations in the brain (Robertson, 1998, for a summary of the findings). This linkage and others can be exploited through an examination of the work on brain-lesioned patients and dreaming.

Neuropsychology and Dreaming

Intrigued by reports of changes in dreaming or the complete loss of dreaming by some of the patients he examined as part of his clinical work, neuropsychologist Mark Solms (1997) questioned 361 consecutive patients in detail about possible changes in the frequency and nature of their dreaming. Twenty-nine patients turned out to be free of any brain lesions. They were used as a control group because they had been faced with the possibility of brain injuries, admitted to the hospital, and subjected to the same routines and tests as the patients who did suffer lesions.

Solms correlated the 332 brain-lesion patientsí responses concerning changes in their dreams with the findings from their neurological tests and brains scans. This analysis led to the conclusion that there are two different types of dreaming deficits, loss of visual dreaming and complete loss ('cessation') of dreaming . There are also two types of dreaming excesses, increased frequency of dreaming and increased nightmare frequency. All four types of changes in dreaming correlate with waking cognitive defects. In addition, they relate to five relatively specific brain sites. Solms then integrated his findings with those from 73 published studies mentioning deficits and excesses in dreaming that are scattered throughout a neurological literature that goes back over 100 years. The result is a new neuropsychological theory describing the network of brain areas that provides the basis for dreaming (Solms, 1997; 2000).

Solms first found that 200 of the 332 patients with brain lesions reported no changes in dreaming, which is highly useful information in and of itself because it reveals those parts of the brain that are not necessary for dreaming, namely, the dorsolateral prefrontal cortex, the sensorimotor cortex, and the primary visual cortex. This finding is for the most part supported by PET scan studies of REM sleep (Braun et al., 1998; Heiss, Pawlik, Herholz, Wagner, & Wienhard, 1985; Maquet et al., 1996), but there are some disagreements among these studies. More such studies, hopefully employing fMRI and other new imaging techniques, are necessary before neuroimaging studies can be considered as useful as Solmsí clinico-anatomical findings for developing a neuropsychological theory of dreams.

Turning to the 132 patients who reported changes in their dreaming, Solms (1997) found 112 patients with forebrain lesions who lost dreaming for varying periods of time or permanently. Since none of these patients had brainstem injuries, these findings show conclusively that REM sleep is not sufficient for dreaming. The loss of dreaming turned out to be due to two different types of forebrain lesions. Most of these patients--103 in all-- had injuries to one or both of the parietal lobes, which are essential to spatial representation, the mental rotation of objects, and the orientation of attention. For many of these patients, dreaming returned when the lesions healed. They also showed a decline in waking visuospatial abilities while dreaming was absent, which provides independent evidence for Foulkes' (1999) conclusions about the importance of visuospatial skills in the development of dreaming. This finding led Solms (1997) to the hypothesis that the cortical network for spatial representation, located primarily in the parietal lobes (Robertson, 1998), is essential for dreaming.

The other 9 cases of complete loss of dreaming had bifrontal lesions in the white matter inferior to the frontal horns of the lateral ventricles, an area that provides a crucial link between limbic structures and frontal cortex. While the evidence for the importance of this area may seem weak because it is based on a small number of cases, Solms strengthens his argument by drawing on the previously overlooked literature reporting the complete loss of dreaming in 70-90% of the schizophrenic patients who were lesioned in that area between 1940 and 1975 as a way to control their symptoms (Frank, 1946; 1950; Solms, 1997; 2000). In some of the more recent cases this absence of dreaming was confirmed with awakenings in the laboratory during REM sleep (Jus et al., 1973). It is noteworthy that most of these patients were lacking in initiative, curiosity, and fantasy in waking life. p Third, Solms had 9 cases where injuries in the frontal-limbic region led to reports of excessive and very vivid dreaming of a highly realistic nature. These patients also complained of dreamlike thought in waking life. Observations by hospital staff and the patients' own testimony suggested that they were suffering from a confusion of dreaming and waking thought as well. Fourth, Solms had 9 patients with lesions in the temporal lobe who suffered from greatly increased nightmares of a repetitive nature. These findings correspond with a large literature on the nightmares that often accompany temporal lobes seizures (Penfield & Erickson, 1941). They also correspond with reports of dreamy states when the temporal lobes are stimulated through stereotaxic electrodes in diagnostic studies designed to locate the sites of seizures in epileptic patients for purposes of surgical intervention (Bancaud, Brunet-Bourgin, Chauvel, & Halgren, 1994).

Finally, Solms had two patients with injuries to the visual association cortex, one who lost all visual imagery in dreams for a short time, the other of whom was able to see static dream images from time to time. Both had one or another difficulty in terms of waking mental imagery. These findings correspond with 13 cases that go back to the 1880s in the neurological literature. They are also supported by Kerr, Foulkes, and Jurkovicís (1978) laboratory study of a patient with damage in her visual association cortex who had neither waking mental imagery nor any visual imagery in her dreams. Solms (1997, p. 105) describes his second case as 'strikingly reminiscent' of another patient studied in the laboratory by Kerr and Foulkes (1981).

Generally speaking, the findings on visual deficits in dreaming provide the most detailed evidence for the close relationship between specific dreaming and waking deficits. Patients with lesions in the occipito-temporal region of the visual association cortex lose waking mental imagery and visual dreaming; patients who can no longer recognize faces report that people are faceless in their dreams; people who lose their color vision report the loss of color in their dreams; and patients who lose their ability to imagine movement report that their dreams are like still photographs or a series of slides rather than moving pictures (Solms, 1997).

Solms puts the five lesion sites together as follows to provide the foundation for a neurocognitive theory of dreaming (see Figure 1 for an overview of the system). First, he hypothesizes that the initiating mechanisms of the neural network for dream generation are probably located in the temporal-limbic region because of the increased nightmare frequency in patients with temporal lobe injuries. He argues that this area provides 'affective arousal' (Solms, 1997, p. 243). Second, Solms argues that the frontal-limbic area is a necessary component of the dream generation system that provides an element of 'selectivity' to the dream's content. Third, he argues that the bifrontal white matter is a vital linkage to the frontal lobes from the dopaminergic circuits that provide the 'appetitive interest' necessary for dreaming. This hypothesis is based in good part on the loss of initiative, curiosity, and exploratory interest in the schizophrenics who were lesioned in this area, but a similar waking syndrome was noticed in several of his bifrontal cases as well.

However, these three brain areas are not enough in and of themselves for dreaming to occur because the parietal lobes must be able to provide the critical element of spatial representation. Solms (1997, p. 271) reports there is even some evidence that the left parietal region 'contributes symbolic (quasispatial) mechanisms to the dream process whereas the right parietal region contributes concrete spatial mechanisms,' but he also stresses that this claim needs further investigation. Finally, the visual association cortex located in the occipito-temporal area is necessary for the dream to have a visual aspect.

As can be seen, this theory does not give any direct role to REM sleep in generating dreams. Just as the cessation of dreaming due to parietal lobe or deep bifrontal lesions shows that REM sleep is not sufficient for dreaming, the fact that dreaming can occur in NREM sleep due to temporal lobe seizures shows that REM sleep is not necessary. However, the new theory is consistent with the fact that dreaming most often occurs during REM sleep because the temporal-limbic region that is the trigger site for dreaming is regularly stimulated by the periodic activation of the brainstem (Hobson et al., 2000).

There remain major disagreements between Solms and the REM dream theorists about the role of brainstem mechanisms in triggering the dream state, with the REM theorists insisting that the brainstem mechanisms are essential for dreaming to occur even in the late-night --and allegedly not very dreamlike--NREM dreams Hobson, 1992; Hobson et al., 2000). Nonetheless, there is broad agreement that a forebrain network along the lines suggested by Solms is necessary for dreaming. There is also agreement that this network plays the major role in terms of shaping dream content (Hobson et al., 2000; Hobson, Stickgold, & Pace-Schott, 1998). For those who want to develop a neurocognitive theory of dreams, it is the forebrain network for dream generation that is the real issue.

The argument over the role of REM sleep, which serves as a stalking horse for Hobson's (1988) all-out attack on Freudian theory, and leads to his rejection of all psychological theories of dreams, is beside the point once the problems of all clinical theories are acknowledged and Foulkes' (1982; 1999) cognitive findings are accepted. Furthermore, the continuing new discoveries that force changes in the details of the REM-based theories, along with the disagreements about the implications of their findings among those neuroscientists who work at the cellular and brainstem levels, suggests that it is at best extremely premature to insist on the comprehensive 'mind-brain' theory advocated by Hobson, Pace-Schott, and Stickgold (2000). However, it also would be premature to say that the forebrain system necessary for dream generation is now definitively established. It may turn out to include a few parts that are not yet known, and it is seems very likely that it can be specified in more detail concerning the relative importance of the general areas that have been identified. It also may be the case that studies of dreaming episodes in which the dreamers turn out to be aware they are dreaming will show more activity in the brain areas necessary for self-awareness than normally is the case; this possibility is discussed in the synthesis section.

Moreover, there is much to be learned about how the network actually operates. For example, there is a need to examine Solms' (1997) Freudian-derived speculation that some areas in the frontal lobes may play an inhibitory role that turns impulses away from the prefrontal cortex and sends them 'backwards' to the inferior parietal lobes and the visual association cortex. In addition, the claim that the dream generation system may protect sleep in a fashion hypothesized by Freud would need to be demonstrated in great detail given the adequacy of sleep in preschool children before they develop dreaming and in patients who have lost dreaming. Moreover, it seems likely that mechanisms for maintaining sleep in the face of brainstem activation developed along with REM sleep in early mammals, long before there is any likelihood that dreaming was a part of sleep.

What seems certain is that progress toward an increasingly detailed mapping of this network is inevitable in an era in which neuropsychology is making rapid strides and neuroimaging studies are becoming commonplace. The stage is therefore set for a consideration of lawful dream content of the kind that might be expected from Foulkes' cognitive theory and Solmsí neuropsychological model.

The Content Analysis of Dream Reports

The Hall/Van de Castle coding system is the most comprehensive method for studying dream content that has been develop to date. It is also one of the few that has been used extensively by investigators other than those who created the system, including researchers from Japan, India, Switzerland, and The Netherlands, and it has proven useful with dreams collected by anthropologists in small traditional societies as well (Domhoff, 1996; 2000). The system has 10 basic empirical categories at the nominal level of measurement, which for a variety of reasons is the best level of measurement for studying dream content, including the fact that such categories can be coded with excellent reliability (Domhoff, 1999b; 2000). There is only one assumption underlying the system: the frequency of appearance of an element reveals the intensity of concern with that element.

The ten categories are as follows:

• Characters (humans, animals, and creatures)
• Social Interactions (aggressive, friendly, and sexual)
• Misfortunes and Good Fortunes (e.g., a person is lost or ill; a person finds money)
• Striving (success and failure)
• Emotions (happiness, anger, apprehension, sadness, and confusion)
• Activities (e.g., running, playing, thinking, watching)
• Physical Surroundings (settings and objects)
• Descriptive Elements (e.g., evaluation, intensity, size, velocity)
• Food and Eating
• Elements From The Past

These large numbers are necessary because most dream elements do not appear often enough to be studied reliably with small samples. For example, friendly interactions occur in only 42% of women's dreams and 37% of men's dreams, which means that a sample of 30 dreams from women and 30 dreams from men would have less that 15 observations in each sample on this indicator.

The Quality Of The Data

There is often concern about the quality of the data in studies of dream content because the usual methods of collecting data are not readily utilized. Dream content is relatively unique among areas of psychological study because external stimuli have little or no influence on dreams, which limits the possibility for experimental studies. Furthermore, dreams can't be seen by researchers or reported upon by dreamers while they are happening, so the outcomes of experimental manipulations cannot be studied directly. Studies of dream content are therefore limited to waking verbal reports of memories of a cognitive experience that happened in a very different neurological state. That point holds true even for laboratory studies, so all dream researchers are entirely at the mercy of what dreamers are able and willing to report, and there is no direct way to assess the accuracy of their reports (Foulkes, 1999).

Nonetheless, there is good reason to believe that the dream reports used in Hall/Van de Castle analyses are a representative sample of dreams from a representative sample of people. First, the people who provide dream reports are in general a representative sample of adults on most of the cognitive and personality dimensions psychologists can measure; this claim is based on the finding that there are no reliable differences on these measures between high dream recallers and low dream recallers (Cohen, 1979; Goodenough, 1991; Tonay, 1993). There are two exceptions to this conclusion, those few lacking in visuospatial skills (Butler & Watson, 1985), and those few with 'thin' mental boundaries on Hartmann's (1992) questionnaire for studying the 'boundaries of the mind,' which awaits full psychometric assessment and does not correlate with other personality and cognitive dimensions in any case (Hartmann, Elkin, & Garg, 1991).

Secondly, laboratory studies show there are no differences between dreams reported from awakenings early in the night and awakenings later in the sleep period, which means that any tendency to recall the last dream of the night does not present a problem as far as the representativeness of the recalled dreams (Dement & Wolpert, 1958; Domhoff & Kamiya, 1964; Foulkes, 1966; Hall, 1966b). Third, carefully controlled studies by Foulkes (1979; Weisz & Foulkes, 1970) show that there are no differences between dream reports collected from the same participants in the laboratory and at home, except on aggression in adult dreams. This finding is supported by a reanalysis by Domhoff & Schneider (1999b) using effect sizes to look at seemingly contradictory conclusions reported by Hall (1966b); the study showed that the only systematic differences of any consequence in his large-scale study were on some of the indicators concerning aggression. Overall, Domhoff and Schneider's (1999) results suggest that large samples collected outside the laboratory can be useful for studies of dream content.

Fourth, the fact that most people don't feel "responsible" for their dreams makes them quite willing to provide candid accounts, especially when the reports are voluntary and anonymous, as they are in most Hall/Van de Castle studies. Fifth, any distortions that volunteers may introduce into their reports concerning sexual or aggressive elements have no effect on the Hall/Van de Castle indicators that are important in developing a good understanding of dream content. Sixth, the dream journals kept by a wide range of people for very different reasons are useful unobtrusive measures because they are uninfluenced by the expectations of dream content analysts and lead to similar results despite the disparate motives for which they were kept (Webb, Campbell, Schwartz, Sechrest, & Grove, 1981). In short, the overall quality of the data is surprisingly good (Domhoff, 1996; 1999b).

Relevant Findings

Drawing on many investigations using the Hall/Van de Castle system, four general results emerge that are useful in developing a neurocognitive theory of dreams. First, the system has produced a set of normative findings based on the dreams of college men and women at Case Western Reserve University and Baldwin Wallace College from 1949-1951 (Hall & Van de Castle, 1966). These norms have been replicated with samples from the University of Richmond in 1980 (Hall, Domhoff, Blick, & Weesner, 1982), the University of California, Berkeley, in 1986 (Tonay, 1990/1991), Salem College in 1987 and 1990 (Dudley & Fungaroli, 1987; Dudley & Swank, 1990), and the University of California, Santa Cruz, in 1992 (Domhoff, 1996). Methodologically, the norms are important as the basis for studying unique individuals or groups that might be of special relevance for building bridges to the neural network for dreaming. Theoretically, the norms and the replications are significant because they reveal that college men and women in the United States had the same dream life throughout the second half of the 20th century despite major cultural changes.

The second discovery, as unexpected as the historical continuity in the dreams of college students, is that there is little or no change in dream content with age once adulthood is reached. That is, older dreamers do not differ from the young adults on whom the norms are based, except perhaps for a decline in physical aggressions and negative emotions (Cote, Lortie-Lussier, Roy, & DeKoninck, 1996; Hall & Domhoff, 1963; 1964; Howe & Blick, 1983; Strauch, 2000; Zepelin, 1980). Nor does dream content change much in longitudinal studies of dream journals provided by adults, a claim that holds true for periods as long as four or five decades and for people still keeping journals in their late 70s (Hall & Nordby, 1972; Smith & Hall, 1964; Van Rompay, 1999). There are two important implications to be drawn from these findings. Methodologically, they mean that the norms can be used to study individuals or groups of any age. Theoretically, they mean that any viable neurocognitive theory of dreams has to be compatible with this large body of cross-sectional and longitudinal findings.

The third relevant result with the Hall/Van de Castle system is that there is a stable pattern of cross cultural similarities and differences. Everywhere in the world, for example, women and men have the same differences in the ratio of male to female characters in their dream reports, with women dreaming equally of men and women, and men dreaming about other men by a 2:1 ratio (Hall, 1984). For both men and women, there is usually more aggression than friendliness, more misfortune than good fortune, and more negative emotions than positive emotions (Domhoff, 1996). In addition to these similarities, there are also a few differences that make sense in terms of large-scale cultural differences. Small traditional societies have a higher animal percent, and there are variations from society to society in the percentage of all aggressive interactions that are physical in nature, although it is also the case that men in almost all societies have a higher physical aggression percent than women (Domhoff, 1996; Gregor, 1981; O'Nell & O'Nell, 1977).

Fourth, studies of dream journals have demonstrated wide individual differences in high and low frequencies on a variety of Hall/Van de Castle indicators that are in general continuous with the waking conceptions and past or present emotional preoccupations of the dreamers. That is, contrary to Jung's (1974) emphasis on the compensatory nature of dreams, in which aspects of the personality neglected in waking life are highlighted in dreams, there is a continuity between dream content and waking thought (Bell, 1971; Domhoff, 1996; Hall & Nordby, 1972). This finding leads to the hypothesis of a 'continuity principle' in dreams that is compatible with Foulkes'(1967; 1982; 1999) findings in laboratory studies with both children and adults. This hypothesis is best demonstrated by blind analyses of dream journals where nothing is known about the dreamer until she or he later answers questions developed on the basis of the content analysis (Domhoff, 1996).

Replies by the dreamers to individually tailored questions are used in these studies because personality tests, whether of the projective or objective variety, have not proven as useful as might have been hoped despite the generally consistent nature of the results with them (Domhoff, 1996). The continuing critique of personality tests because they cannot really deal with the make-up of individual cases also suggests that it is prudent to move forward without a large investment in trait-based testing (Cervone & Shoda, 1999). Using the individualistic approach, the confirmatory replies to inferences based on blind analyses has led to the important conclusion that dreams are not primarily about personality as it is conventionally defined. Instead, dreams are about interests, wishes, hopes, fears, and worries. Put another way, the Hall/Van de Castle system reveals what is on the dreamer's mind, not a constellation of personality traits or a clinical diagnosis, which means that it lends itself to the development of a neurocognitive theory of dreams.

The Repetition Principle in Dreams

Several of these discoveries with the Hall/Van de Castle system, and especially the consistency in what adults dream about throughout most of their lifetimes, lead to the idea that there is a 'repetition principle' in dreams (Domhoff, 1993; Domhoff, 1996). This tendency to repeat has gone unnoticed by those who study one dream at a time with clinical patients, use samples of individual dream reports from groups of people, or hold to Jung's (1974) theory that a dream series shows a pattern of symbolic change toward greater personal integration. The idea of a repetition principle in dreams not only accounts for the consistency over years and decades in characters, social interactions, activities, and settings in longitudinal studies using the Hall/Van de Castle system, but it encompasses and makes sense of four other aspects of dream life that must be comprehended within a neurocognitive theory of dreaming.

First, there is a large clinical literature on the repetitive nightmares of posttraumatic stress disorder that fits well with the idea of a repetition principle (Hartmann, 1984; Kramer, Schoen, & Kinney, 1987). These dreams are so persistent and frightening that they forced Freud to partially abandon his wish fulfillment theory of dreams with the statement that 'ìt is impossible to classify as wish fulfillments the dreams we have been discussing which occur in traumatic neurosis, or the dreams during psychoanalysis which bring to memory the psychical traumas of childhood' (1920). More generally, there are few if any extant theories that can easily encompass these dreams, which have a waking cognitive parallel in the flashbacks that often accompany this disorder. True, only a small percentage of people suffer from such dreams, but they must be accounted for nonetheless by any adequate theory, and they may be an especially good bridge to the neuropsychological network for dreaming.

Second, the repetition principle can encompass the recurrent dreams that 50-80% of people claim to have had at one time or another in their lives, often starting in late childhood or early adolescence, and sometimes lasting for the rest of their lives (Cartwright & Romanek, 1978; D'Andrade, 1985; Robbins & Houshi, 1983). Like posttraumatic stress disorder nightmares, recurrent dreams are usually highly negative and emotionally upsetting. Unlike PTSD nightmares, however, they cannot be regularly shown to have their origins in what can be called traumatic events, even if that term is stretched to include family tensions.

Third, the idea of a repetition principle can incorporate the repeated themes found in most series of 20 or more dreams Hall, 1947; 1953c; Hall & Nordby, 1972; Jung, 1974; Mattoon, 1978). In other words, it is not just Hall/Van de Castle indicators that are consistent over many years, but also more general themes like being lost, preparing meals, or being late for an examination. In a journal consisting of 904 dreams over a 50 year period, just six themes accounted for at least part of the content in 76% of the dream reports. In 25% of the dreams the dreamer was eating or thinking about food; in 17% she had lost her purse or some other possession; in 10% she was in a small or disorderly room; in another 10% she was interacting with her mother; in 8% she was trying to go to the toilet, usually being interrupted in the process; and in 6% she was concerned about being late or missing a train or bus (Domhoff, 1993).

Finally, the idea of a repetition principle can encompass 'typical' dreams, such as flying under one's own power, having teeth fall out, or finding oneself inappropriately dressed in public. Content analyses of hundreds of dream reports in journals kept during college courses demonstrate that such dreams account for less than 2% of dream life, so they are not very frequent (Barrett, 1991; Domhoff, 1996). However, several survey studies suggest that at least a significant minority of respondents claim to have had one or more such dream at least once (Griffith, Miyago, & Tago, 1958; Nielsen, Zadra, Germain, & Montplaisir, 1999; Ward, Beck, & Rascoe, 1961). There are reasons to be wary of exact figures from such survey studies because most people do not have a very accurate idea of what they dream about, and therefore may answer on the basis of cultural beliefs about dreams, but typical dreams do happen often enough that they have to be explained. Moreover, they are of potential interest because of their stereotypic content, and they may provide a bridge to waking cognition.

Ideas Toward A Synthesis

This section uses the disparate literatures discussed in the three previous sections to explore some of the intersections between cognitive development, neuropsychology, and dream content that might be of value in developing a neurocognitive theory of dreams. It begins with the links between cognitive development and the neuropsychology of dreaming, then turns to the connections between neuropsychology and dream content, and concludes with the possible relationships between dream content and waking cognition. The main causal connections to be discussed are presented on the sides of the triangle in Figure 2, along with several examples of the kinds of questions that might be answered through future studies. Cognition and Neuropsychology

The first and most important hypothesis that might lead to a neurocognitive theory of dreams is that the gradual development of dreaming in children may correlate with the maturation of the neuropsychological system necessary for dreaming in adults. If the low levels of dreaming in children and the differences in their dream reports from normative adult findings are treated as if they were 'deficits,' then the search could be made for possible causal 'defects' in the neuropsychological network necessary for dreaming. This strategy has been used by Welsh, Pennington, and Groisser (1993) in studying the development of frontal lobe executive functions in children using neuropsychological tests in conjunction with standard developmental tests.

This approach is suggested most strongly by the parallel between the dependence of dreaming in children on visuospatial skills, which are based primarily in the parietal lobes, and the loss of dreaming in adults with injuries to either parietal lobe. The static nature of preschool children's dreams and the absence of movement imagery in the dreams of adults with lesions in specific parts of the visual association cortex might provide another useful linkage. In addition to studying the maturation of the brain structures necessary for dreaming in adults, it also might be useful to adopt Solms' strategy by looking for dreaming deficits in children with a wide range of neurological disorders. For example, Foulkes (1999) has raised the question of whether or not autistic children have the ability to dream, and they may not if the lack of reports from three REM sleep awakenings over two nights in a 25-year-old patient with Asperger's Syndrome are any indication (Godbout, Bergeron, Stip, & Mottron, 1998). That is, the eventual understanding of the neuropsychology of autism and other childhood neurological disorders may also help to understand the development of parts of the neural network necessary for dreaming.

The intersection of cognition and neuropsychology also might shed light on the occasional occurrence of an awareness of dreaming during a dream, a phenomenon that enjoyed a flurry of attention and speculation in the 1980s under the morally toned label of 'lucid dreaming,' which implies a superior or elite status for 'lucid dreamers' (Gackenbach & Bosveld, 1989; LaBerge, 1985; LaBerge, Nagel, Dement, & Zarcone, 1981). If dreaming is the form that consciousness takes during sleep, and if changes in the neural network for dreaming underlie dreaming states, then 'lucid' dreaming may simply be a product of a dream state in which brain centers having to do with self-awareness are more active than is the usual case. This speculation is consistent with the finding that higher levels of alpha activity during REM sleep are related to lucid dream reports (Tyson, Ogilvie, & Hunt, 1984), as is the fact that self-awareness during REM sleep is associated with phasic activation within the REM period (Bradley, Hollifield, & Foulkes, 1992). So is a finding on the more 'realistic' nature of the content of lucid dreams in a study using Hall/Van de Castle coding categories (Gackenbach, 1988). In addition, it is noteworthy that dream reports in an exploratory PET scan study of l2 male participants showed a greater sense of control when the medial frontal cortex and rectal orbital gyrus were more active, and a greater sense of things being out of control when the amygdalae were most active (Shapiro et al., 1995).

There is also non-laboratory evidence suggesting that a 'lighter' stage of sleep closer to waking fantasy life may be the only explanation needed for this phenomenon: most lucid dreams happen late in the sleep period when sleep consists of REM and Stage II of NREM. In fact, lucid dreams seem to happen most often after an early morning awakening that is followed by imagery rehearsal and a conscious attempt to be aware of dreaming upon falling back to sleep (LaBerge, 1985). Whether these people are in REM sleep or Stage II NREM, the new question of interest due to Solms' findings is the overall state of the neuropsychological network that generates dreams.

Neuroimaging studies of people during lucid dreaming might even be useful in learning more about the parts of the brain involved in self-awareness. That is, the difference between the brain during a lucid dream and a typical dream might be precisely those parts of the brain that are necessary for such awareness.

Neuropsychology and Content Analysis

The repetition principle provides the first and most promising link between dream content and the neuropsychological network for dreaming, particularly in terms of its possible relationship with the vigilance/fear system that seems to be centered in the amygdala (LeDoux, 1996; Whalen, 1998). The best examples of this point, of course, are the repetitive nightmares of posttraumatic stress disorder, which sometimes happen in Stage II of NREM sleep (Van der Kolk, Blitz, Burr, Sherry, & Hartmann, 1984) and seem to have parallels with the nightmares suffered by epileptics due to seizures in NREM sleep (Solms, 1997; 2000). There is also evidence that PTSD patients studied in the sleep laboratory have fewer contemporary settings in their REM dream reports in general (Dow, Kelsoe, & Gillin, 1996).

Then, too, studies using stereotaxic electrodes to locate the sites causing seizures in epileptic patients show that the 'dreamy state' sometimes experienced as part of the diagnostic process are related to the temporal-limbic region; in one large-scale study the amygdala, anterior hippocampus, and temporal neocortex were involved in every spontaneous occurrence of this state during the procedure (Bancaud et al., 1994) . Thus, future neuroimaging work on both posttraumatic stress disorder and epilepsy may hold promise for linkages between the repetition principle and the neuropsychology of dreaming.

However, there need not be an exclusive focus on patients. The consistency of emotionally painful themes and of heightened scores on Hall/Van de Castle indicators in the dreams of many normal participants suggest that their dream life is often 'stuck' in the past in a way that fits with the persistence of negative memories stored in the vigilance/fear system (Block, 1999; Bowen & Dunn, 1999; Domhoff, 1996). Both dreams and the vigilance/fear system provide a neurocognitive record of traumas, upsets, and tensions over a lifetime. Neuroimaging studies of people while they are experiencing one of their repetitive negative themes might be able to provide a more specific picture of why there is more aggression than friendliness in dreams and why negative emotions outnumber positive ones by 4:1.

Systematic studies showing the effects of different drugs on dream content, when done in conjunction with neuroimaging studies, might help to pinpoint relationships between dream content and specific components of the dream-generation network. The promise for such studies is seen in the fact that both alkaloids (Cartwright, 1966; Ketchum, Sidell, Crowell, Aghajanian, & Hayes, 1973) and dopamine (Hartmann, Russ, Oldfield, Falke, & Skoff, 1980; Solms, 1997; 2000) intensify the dream experience.

Patients suffering from epilepsy or Parkinsonís might be potential candidates for content studies because it already is known that the medications that eliminate epileptic seizures also reduce or eliminate the patients' nightmares, and that L-dopa potentiates the dream experience for Parkinsonís patients (Bearden, 1994; Hartmann, 1984; Solms, 1997). Content studies might be able to determine whether or not the types of settings, characters, activities, and social interactions in the dreams of people taking such substances change in ways that might be expected on the basis of what is known about the way in which they impact specific sites within the neuropychological network for dreaming.

Although earlier content studies on the effect of drugs on dreams led to few clear results for a variety of reasons (Roth, Kramer, & Salis, 1979), the potential for pre/post studies of individual cases is shown in the large positive changes in the dream content of a 21-year-old woman after she began taking an SSRI to cope with anxiety attacks (Kirschner, 1999). These positive changes include more friendly interactions, less aggressive interactions, and less negative emotions. In terms of the repetition dimension as an indicator of fixation to the past, it is also of interest that she showed a decline in elements from the past as well (see Figure 3 for an overview of the continuity and change in her dream content).

The fact that the dream content became more positive in Kirschner's (1999) study also provides a strong reminder that not all dreams are negative. Nor do all people with painful pasts necessarily have negative dreams in the present. The positive content in dreams could be studied by using neuroimaging and neurochemical methods with people whose dreams are more positive than is usually the case.

Dream content and neuropsychology also might be linked by investigations that correlate specific neuropsychological defects with atypical scores on Hall/Van de Castle indicators, or that track the relationship between the return of dreaming after parietal lobe injuries and changes in dream content. That is, just as specific language defects in the aftermath of strokes or organic brain diseases often relate to the specific location of the lesion, perhaps it might be possible to link changes in dream content to specific defects in the dream-generation system. Studies employing the Hall/Van de Castle categories for activities and objects also might be useful for examining Solms' (1997) hypothesis that the left and right parietal lobes serve slightly different functions in the construction of a dream.

The potential for such studies is demonstrated in older reports cited by Solms (1997) showing a decline in 'narrative complexity' in the dreams of patients with specific defects through injuries or operations. It is also seen in the finding that 17 male chronic brain syndrome patients had more family members, less aggression, and less emotional content in the 31 dreams they reported than did the Hall/Van de Castle normative sample. This array of findings suggests that their dreams were very bland, a characterization which fits with their waking personalities (Kramer, Roth, & Trinder, 1975; Torda, 1969).

It might even be that there is a different profile on Hall/Van de Castle indicators for each type of neuropsychological defect. An example of this possibility with mental patients is shown in Figure 4, which presents the differences between a sample of 104 dreams collected from 20 male schizophrenics in the early 1960s and the Hall/Van de Castle norms for males. As can be seen, the patients were lower in the percent of characters who were friends, in the index of friendly interactions per character, and in the percentage of dreams with at least one friendly interaction. This set of findings has been reported in several studies of mental patients (Hall, 1966a; Kramer, 1970; Kramer & Roth, 1973; Maharaj, 1997; Schnetzler & Carbonel, 1976).

Dream Content and Cognition

The continuity principle established through blind analyses of individual dream journals provides a strong link between dreaming and waking cognition because it shows that both of these cognitive states are dealing with the same psychological issues to a large extent. It provides the basis for a cognitive theory of dreams which starts with the idea that dreams express our conceptions of self and others (Foulkes, 1985; Hall, 1953b). The emphasis is on conceptions of 'self' and 'others' because studies of adult dream content show that dreams reflect relatively little about a person's attitudes toward current events and politics (Hall, 1951). Similarly, (Foulkes, 1982; 1999) found that children between ages 5 and 15 dreamed very little of their two most time-consuming daytime activities, going to school and watching television; instead, they dreamed about recreational activities.

This emphasis on the highly personal nature of dreams also may explain why the dreams of college students in the United States have not changed over the past 50 years; the culture has changed, but personal concerns probably remain very stable. This emphasis also may explain why dreams are more similar than they are different around the world. As anthropologist Thomas Gregor (1981, p. 389) suggests at the conclusion of his detailed study of 385 dream reports from men and women in a very small native group deep in the Amazon jungle, 'it may be possible to show that the dream experience is less variant than other aspects of culture.'

However, as the evidence concerning the importance of the repetition principle shows, the continuity principle does not operate entirely in terms of current personal interests and concerns. Dream content is also continuous in varying degrees for different individuals with past waking concerns. Discrepancies between current waking concerns and dream content, such as dreaming about painful events that the person no longer thinks about in waking life, could be used to see how the continuity and repetition principles interact with each other to shape dream content.

Studies of dream content also might be able to provide a link between waking cognition and dreaming to the degree that they can identify the use of the same conceptual metaphors, metonymies, and conceptual blends in dreams that have been shown by cognitive linguistics and psycholinguists to be pervasive in waking thought (Fauconnier, 1997; Gibbs, 1994; Gibbs, 1999; Lakoff & Johnson, 1980; Lakoff & Johnson, 1999). Although strategies for locating metaphors in a dream series through the use of content analysis go back several decades (Hall, 1953a), very little progress has been made in this direction. Lakoff (1993; 1997) presents new ideas for studying metaphors in dreams that provide additional starting points, as demonstrated by Dunn (1999).

One avenue into this possible linkage might be found in the typical dreams discussed in the previous section as one point along the repetition dimension. These dreams may be examples of 'primary' metaphors, which are based on repeated correlations between two dimensions of experience that are common in childhood development, such as lifting a heavy object and experiencing strain, leading to the metaphor that 'difficulties are burdens' (Grady, 1999). Consider dreams of flying under one's own power, which are experienced by a little over half of college students in two surveys, and said by them to be generally positive in feeling tone (Domhoff, 1996). Searching for a metaphor related to flying, the possibility arises that these dreams may be instances of the primary metaphor 'Happiness is Up,' as found in such expressions as 'high as a kite,' 'walking on air,' and 'floating on cloud nine.' This speculation also fits with the fact that people sometimes become apprehensive about falling during their positive flying dreams, just as people worry that they may 'crash' or have 'the air let out of their balloon' when they are too elated in waking life.

Similarly, it may be that dreams of appearing inappropriately dressed in public are instances of the metaphor 'Embarrassment is Exposure,' which is expressed through such well-known phrases as 'caught red-handed,' 'caught with egg on your face,' or 'caught with your pants down' (Holland & Kipnis, 1994). It might be evidence for this conjecture that people who are asked to write down the dream in which they experienced the greatest feeling of embarrassment most often report one in which they are inadequately attired in a public place (Domhoff, 1996).

These two hypothetical examples aside, the few attempts to undertake systematic studies of metaphor in dreams suggest that most dreams do not seem to relate very obviously to primary metaphors (Hall, 1953a). Most dreams seem more like dramas or plays in which the dreamer acts out various scenarios that revolve around a few basic personal themes (Hall, 1947). They seem to be instances of the 'thematic' point on the repetition dimension, that is, specific 'examples' of more general emotional preoccupations, usually negative in nature, but not always. This means that less obvious forms of metaphor or other types of figurative thinking must be invoked if very many dreams are to be encompassed by the ideas of cognitive linguists.

These more complex dreams may rely on 'resemblance' metaphors, which depend upon the perception of the common aspects in two representational schemas (Grady, 1999), or on conceptual blends that often start with basic conceptual metaphors and then are elaborated into highly novel thoughts (Grady, Oakley, & Coulson, 1999). Lakoff (1993) demonstrates how a resemblance metaphor might be applied to dreams by analyzing a dream told to him by a woman who had recently married a professor, but was concerned the marriage might fail for financial reasons. In the dream she was back in college taking a class from her favorite male professor. The professor walked over to her and said she was not working hard enough, and therefore would fail the course.

Using his knowledge of the woman's personal life, Lakoff suggests that the dream can be linked to her waking concerns about her marriage due to the fact that both situations are perceived by the dreamer as sharing a resemblance, a fear of failure in a relationship with a favorite professor. That is, the dream is a metaphoric example of her underlying concern based on the resemblance between the feelings and perceptions she had when she was a student of one favorite professor and now when she is married to another favorite professor. While this example might be more convincing if it were based on a blind analysis in which nothing is known about the dreamer, such blind analyses of individual dreams are only possible when a large number of dreams from the person is available. In that context, Hall (1953a) has shown that blind analyses of a series of dreams can lead to very plausible and potentially verifiable metaphoric inferences about dream content when resemblance metaphors relating to a major concern are utilized several times in the dream series.

To take his best example, a young woman who provided a series of dreams had an especially striking dream in which she was searching for her wedding gown because she and her husband were to be married again on their first wedding anniversary. However, she was very disappointed when she found the gown: it was dirty and torn. With tears in her eyes, she put the gown under her arm and arrived to the church, only to have her husband ask why she had brought the gown. She reports she was 'confused and bewildered and felt strange and alone.' (Hall, 1953a, p. 179) Looking at the dream from a metaphoric point of view, Hall hypothesized that the state of the dress might express her conception of her marriage. In today's terms, the dream may be a conceptual blend based upon a metonymy.

To test this hypothesis, Hall looked to see if there were other dreams in the series that might suggest the marriage is in difficulty, and there were several: (1.) the stone from her engagement ring is missing; (2.) her husband has tuberculosis; (3.) one of her women friends is going through a divorce; and (4) a friend who is about to be married receives a lot of useless bric-a-brac for wedding presents. Now that the Hall/Van de Castle system is available, future cases of this type also could compare her aggressions-per-character ratio with her husband to the same ratio with other adult males.

Moreover, future studies of figurative thought in dreams based on dream series could incorporate two further steps. First, they could interview the dreamer once the blind analysis is completed. Second, they could ask friends and relatives of the dreamer about the issue in question. In the case of the woman discussed above who seemed to be unhappy with her marriage, the inference would be considered correct if she agreed with it, or if her friends and relatives said she was unhappy in her marriage, even though she did not report to the investigators that she was. In the latter scenario, it could be said that she had a 'blind spot,' metaphorically speaking, about this key conception in her life. However, and importantly, if both the dreamer and the other people interviewed deny the inference, then it must be counted as incorrect. In short, this methodology provides a cognitive approach to inferences about 'unconscious' thoughts that has the great virtue of being eminently falsifiable .

The possibility that some dreams are based on figurative thinking provides a way for a neurocognitive theory of dreams to incorporate the interesting idea that past experiences are sometimes used to express current conflicts that have similar emotions and feelings at their core (Kramer et al., 1987). This idea comes from a study of Vietnam vets who had recovered from their posttraumatic stress disorder. However, they later came back to the Veterans Administration for help when war-related themes began to appear in their dreams in the face of new life stressors, such as marital conflict, conflicts with children, or work-related conflicts. In effect, the war-related dreams are conceptual blends that combine past experiences with aspects of the stressful situations they are now enduring. The resemblance is in the similarity of the feelings in both the war and the new situation--'itís a war-zone out there,' they might be thinking in relation to their current problems.

To date, the few investigations of the relationship between metaphoric thinking and dream content have focused on adults, but it also might be possible to study the development of metaphoric thinking and dreaming in children. For example, McKay and Konishi (1980) show that the animals in children's stories socialize children concerning stereotypic gender roles by means of personification. This finding might be a starting point for understanding the high percentage of animal characters in children's dreams (Van de Castle, 1983). It also might be helpful to see if the first appearances of typical dreams parallel the ability to make use of the relevant primary metaphors in waking thought. Then, too, it might be possible that children's dreams become more complex as they develop the ability and store of knowledge to use sophisticated resemblance metaphors; if so, this may relate to Foulkes' (1982) finding in his longitudinal study that personality differences did not show up very consistently in dream content until preadolescence.

If dreaming is in good part figurative, especially in terms of primary metaphors, resemblance metaphors, and metonymies, then a neurocognitive theory of dreams could advance in parallel with new understandings in cognitive linguistics. Such a linkage would be a very gratifying result at the theoretical level. However, it still would be necessary to do the same kind of thematic and Hall/Van de Castle content analyses of a dream series that have been carried out in the past in order to understand any given series of dreams because many resemblance metaphors are likely to be unique to the dreamer. Moreover, several different primary metaphors sometimes use the same source domain, such as 'vertical orientation,' so contextual analysis would be necessary to decide among such possibilities as 'Happy is Up,' 'More is Up,' and 'Control is Up' (Lakoff & Johnson, 1999, pp. 50-53) .

In closing this section on cognition and dream content, it needs to be stressed that there is little or no systematic evidence that dreams make use of the vast system of figurative thought available to most individuals through a combination of developmental experiences and cultural heritage. Of all the possible linkages among the three areas of dream research suggested in this paper, the idea that dream content studies may provide bridges to the insights of cognitive linguistics is by far the most speculative.

Discussion and Conclusion

There are other linkages among the three areas of dream research discussed in this paper, but enough has been said to demonstrate that there is now a large body of established empirical findings upon which it is possible to base a new neurocognitive theory of dreams. This theory builds on a newly discovered neuropsychological network of dream generation, links that network to the gradual development of dreaming in children, and then studies dream content as the result of the interaction between the continuity and repetition principles, with an eye out for the possibility that the thinking during dreaming in adults is at least in part figurative. Each of these linkages has something to contribute to an emerging synthesis on dreams, and a new neurocognitive theory would be incomplete if it left out any of them.

This theory also could be related to theories of waking cognition because of the several parallels between waking cognition and dreams, only some of which have been explored in this paper (see Cavallero & Foulkes, 1993, for the full range of studies). Recalling Foulkes' (1999) insights about the possible relationship between the development of dreaming and the development of consciousness, it might even be that a neurocognitive theory of dreams could add a new dimension to consciousness studies. The idea that the ability to portray oneself as an active dream character is an index of an adult-like self-consciousness may be an especially promising avenue.

Moreover, the research tools are now available to make the many necessary studies possible. The rapid advances in neuroimaging are the most obvious examples of this point, but the advent of personal computers and the constant improvements in software have made content analysis somewhat less labor intensive and far more accurate than it was in the past (Schneider & Domhoff, 1995). It is also now possible to use a new program called DreamSearch to analyze thousands of dreams from many different individuals at the same time for single words, strings of words, or phrases, and then to make detailed comparisons among types of dream reports (Schneider & Domhoff, 1999). DreamSearch may prove especially useful for metaphoric studies (Dunn, 1999).

If the history of dream research in the twentieth century is any indication, the prospects for a new synthesis are not certain even if the many new findings and methods call out for one. The staying power of the rival clinical theories originating in the early decades of the century stands as a somber reminder that the study of dreams is nearly unique among scientific areas of research in its resistance to new theories. So, too, does the continuing interest in theories that equate dreaming with REM sleep even though such theories were toppled for most empirical dream psychologists in the 1960s by the discovery of solid evidence for NREM dreaming (Berger, 1967; 1969; Foulkes, 1966; Hall, 1967; Kamiya, 1961). However, there is one ray of hope that the reign of unlikely dream theories may soon end. If the developments in the cognitive sciences in general in the past 20 years are any indication of things to come, then it is likely that the study of dreams will be incorporated into the scientific mainstream through a neurocognitive theory of dreams. This paper offers the starting point for how this process of incorporation might take place.

Table 1. The Formulas For Calculating Hall/Van de Castle Content Indicators.

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