Dream Bizarreness Reconsidered

EDITORIAL Dream Bizarreness Reconsidered Claudio Colace, Ph.D.

INTRODUCTION reams frequently show impossible and/or improbable aspects compared with common life experiences, which have been referred to as “dream bizarreness”. Although the issue of dream bizarreness has already been discussed by the psychoanalytic dream theory, the first systematic investigations on this aspect of dreaming only began in the Sixties, when a few authors started attempting to measure dream bizarreness by objective indicators (1-3). The “activation-synthesis” model (4) later proposed a first systematic attempt to explain the causes of dream bizarreness after Freud’s initial hypothesis. This model was based on the neurobiological events of REM sleep and opened a new perspective to investigation. However, it automatically invalidated the psychoanalytic approach and therefore excluded any sort of analysis of psychological or motivational determinants. At the same time the cognitive-psychological approach to dreaming processes (5,6) was limited to analysing dream bizarreness generation mechanisms (i.e., “how”) rather than its possible reasons and causes (i.e., “why?”). Therefore, investigations on the causes of dream bizarreness were restricted to the neurobiological level alone. Still according to the more recently revised versions of the “activationsynthesis” hypothesis, dream bizarreness can be fully explained by the particular

D

Acknowledgments: I am grateful to Dr. Vincenzo Natale for critical reading and constructive comments on the earlier version of this manuscript. Address reprint requests to: Dr. Claudio Colace, Via Luigi Volpicelli, 8, 00133 Roma, Italy Phone: 3336148977 e-mail: [email protected]

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neurobiological conditions that are found only in REM sleep (7-14). In addition, this approach emphasizes the role of PGO (ponto-geniculo-occipital) activity in determining dream bizarreness, on which two other neurobiological models, the “reverse learning” theory (15) and Seligman and Yellen’s model (16) are also grounded. This paper will review the literature on dream bizarreness in order to demonstrate that the current neurobiological approach to dreaming, represented primarily by the “activation-synthesis” hypothesis, is reductive and not consistent with various research data. The paper, after an attempt to define the term “dream bizarreness”, is structured as follows: Theoretical Models (Part I), Measuring Dream Bizarreness (Part II), Empirical Data and Implications (Part III), and Conclusions. DEFINING DREAM BIZARRENESS According to the Webster’s New Collegiate Dictionary, there are two features that define the word “bizarreness”: 1.Improbability (strikingly out of the ordinary) and 2.Unusualness, oddness, extravagance. Several terms have been used in literature to describe bizarreness, for example, “distortion from reality”, “metamorphosis”, “implausibility”, but many authors agree that the concept of bizarreness includes both: a) Impossibility, and b) Improbability and/or oddness compared to “common daily experiences”. The first dimension includes those situations that are impossible from a physical and/or logical point of view; the second dimension implies statistical improbability.

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Dream Bizarreness Reconsidered

Neurobiological approach

phase of sleep “dreaming is the cognitive by-product of a physiological state, REM sleep” (14, p. 202). The original theory stated that bizarreness is the result of a temporally random and non-cognitive input from the brainstem (PGO spikes) and that dreams are merely the product of “the best of a poor job” that the forebrain makes to give sense to this random bombardment (forebrain synthesis) (4). Later on, it was suggested that the aminergic demodulation found in REM sleep (or the lack of the inhibiting influence of norepinephrine and serotonin) causes defects in cognitive functioning (e.g. attention, memory, etc.) during forebrain synthesis, which contributes to dream bizarreness (7,14,2324). More recently, Hobson and others proposed an updated version of the “activation-synthesis” hypothesis, incorporated in a general brain/mind model called AIM (9-10,12-13). According to the AIM model, sleep and waking thought vary in function of three parameters: Activation level (A), Input sources (I) and information-processing Mode (M) (i.e., the aminergic to cholinergic neuromodulation rate). REM sleep is hypo-aminergic (compared to waking state) and hypercholinergic. As in the previous version, this model claims that dream bizarreness is due to an alteration of cognitive functioning caused by the shift from a high level of aminergic neuromodulation during waking state to a low level of same during REM sleep. In Hobson’s view, dream bizarreness is a constant formal property of all dreams. Bizarreness in itself has no particular psychological significance. It is motivationally neutral and its interpretation is gratuitous and probably hasty. Dream is inherently meaningless–a state of the mind similar to delirium or insanity (7,12,14,25-27).

“Activation-synthesis” hypothesis

“Reverse learning” theory

This model ascribes dream bizarreness exclusively to the unique neurobiological conditions of the brain during the REM

According to the “reverse learning” theory, dreaming and bizarreness are merely the result of the effort to erase from

PART I: THEORETICAL MODELS Psychoanalytic theory According to psychoanalytic theory, dream bizarreness is an expression of a motivated effort to disguise unconscious wishes that are unacceptable to the conscience. The Ego and Superego defensive mechanisms are responsible for this effort to disguise latent dream contents. For example, children do not dream bizarre dreams because they have not yet developed the superego which enables these defensive changes of latent dream contents (i.e. psychical censorship functions) (17-21). In adults, bizarreness may be present in direct relation to the state of the individual’s superego at particular moment in time (19). The psychoanalytic theory even classifies dreams according to bizarreness features. Dreams may be as follows: a. “Sensible, plausible and without oddities” - these sort of dreams lack any kind of “censorship” and dream-work activity; b. “Sensible and consistent in itself but odd compared to common life”; c. “Senseless, inconsistent and bizarre”; Types b and c show a moderate and high degree, respectively, of “censorship” activity (17). In Freud’s view, dream bizarreness is not an invariant property of dreams, as there are dreams that are typically nonbizarre (e.g., young children’s dreams, and adult dreams directly engendered by the frustration of vital needs) (19,22). Bizarre elements are psychologically meaningful, and dreams do have a meaning. Motivations play an important role in this model, while other models reviewed give little relevance to them.

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memory redundant associations or “parasitic” thoughts (i.e., information causing an overload in the memory system) during REM sleep. In other words, we dream to forget, or to reduce fantasies in the waking state. Random PGO spikes impinge on the neocortex, resulting in the erasure, or “unlearning”, of false information. As in Hobson and McCarley’s theory, in this model too random subcortical PGO activity plays an important role for bizarreness. Dream is inherently meaningless (15,28).

differences in the bizarre/realistic dreams.

Seligman and Yellen’s theory

Foulkes’s cognitive model

This model is based on “activationsynthesis” hypothesis and on previous studies that had found a relationship between tonic/phasic activities in REM sleep and some aspects of dream mentation (29-31). Seligman and Yellen (16) suggested that dreaming consists of three elements: (i) periodic, unrelated visual episodes (REM burst), (ii) emotional episodes, and (iii) the cognitive synthesis of both of the episodes above during REM quiescence. The bizarreness and discontinuity found in REM dreams are due to the “visual burst” (discharges of eye movements) that supposedly cause intrusions of inconsistent and discontinuous images in the dream plot. The authors suggest that there are two separate forms of visual information/ dream imagery. The first, generated by bursts, is more vivid and disjointed from the underlying plot while the second, generated by cognitive synthesis, is less bizarre. As in Hobson and McCarley’s model, Seligman and Yellen attributed bizarreness to random PGO activity (PGO spikes are commonly associated with visual bursts) and therefore to the difficulty in finding a sense in visual bursts. However, the authors argued that their model also accounts for the banality and realism of certain dreams (32). In other words, while bizarre dreams are due to visual burst activity, realistic dreams are due to a successful cognitive integration. Furthermore, individual differences in individual cognitive styles could explain the

Foulkes (5-6) indicates three components in dream production: the input, i.e. the activation of memory units, their processing, known as “planner”, and the output, i.e. conscious organisation. The dream is an attempt to give a plausible sense to input information. In Foulkes's view this attempt is generally successful. However this dream production mechanism may be disturbed by the presence of memory units with a higher and more impinging level of activation which the planner cannot exclude from processing. This event translates into the presence of thematic changes (i.e., discontinuity) and bizarre elements. Therefore bizarreness is considered an exception rather than the rule. Indeed Foulkes, based on the results of previous studies, suggests that the content of representatively sampled dreams (REM dreams) of both adults and children are generally realistic and ordinary, rather than fantastic and bizarre (32-35).

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frequency

of

Cognitive approach The cognitive approach assumes that dreaming is probably distributed along all sleep stages (particularly–but not limited to–the REM and 2-NREM stage) and that there is a common generative system for dreaming and waking fantasies. This approach is principally interested in studying dream production processes.

Antrobus’s General Cortical Activation/ Thresholds (GCAT) model According to Antrobus and colleagues, bizarre mentation is the product of two factors: cortical/cognitive activation and the level of environmental stimulation (or auditory thresholds) (36-41, Klinger’s study as cited in 39,42). Reinsel et al. (39) found that bizarreness is maximal in conditions of high to moderate 107

108 yes yes

Bizarreness has a psychological meaning

Influences of motivations on dream bizarreness production

/

Bizarreness is explained exclusively by neurobiological events of REM sleep

yes

A generative system of dreaming and waking imagery, including bizarreness, is common /

no

Bizarreness is exclusive to dream mentation

Bizarreness is present even when PGO activity is notably reduced

no

Psychonalytic

Bizarreness is an invariant property of dreams

Questions about dream bizarreness

Psychological

no

no

yes

no

no

yes

yes

no

no

yes

no

/

yes

yes

Reverse learning theory

no

no

yes

no

no

yes

no

Seligman and Yellen’s theory

Neurobiological Approach Activationsynthesis hypothesis

Table 1. Current models for dream bizarreness: Questions about dream bizarreness

no

no

no

/

yes

no

no

Foulkes’s cognitive model

no

no

no

yes

yes

no

no

Antrobus’s (GCAT) model

yes

yes

no

/

yes

no

no

Hunt’s phenomenological perspective

Cognitive Approach

Dream Bizarreness Reconsidered

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cortical/cognitive activation when external stimulation is minimal (i.e., REM sleep and relaxed waking). REM dreams are not specifically more bizarre than any other form of thought when the environmental conditions and the length of the dream report (i.e., rate of cognitive activation) are under control. For instance, the authors noticed that NREM dreams happen to be more bizarre in individuals with high activation levels during NREM sleep (42). In addition, Reinsel et al. show that bizarreness has many dimensions that can differentiate the quality of bizarre mentation across sleep and waking conditions. Thus, the types of bizarreness depend on the variations of the two parameters above: waking mentation bizarreness (i.e., discontinuity) is due to external stimuli disrupting ongoing mentation (in Reinsel et al.’s study (39) relaxed waking was interrupted at varying intervals); while bizarreness in REM dreams is associated with the more genuinely “strange” nature of the images (i.e., improbable or impossible identities). Improbable combinations (bizarre elements regardless of context) increase and are equally prevailing in relaxed waking (without stimuli) and in dreams. Phenomenological perspective Hunt (43-44) elaborated a “phenomenological classification-ratings system for formal anomalies in the dreaming experience” (see Table 2) and analyzed different samples of dream reports. In particular, laboratory dreams, home dreams, the “most fantastic” and the “most realistic” of home dreams, and dreams collected by Freud and Jung. In Hunt’s view, “normative dreams” (i.e., laboratory and home dreams), albeit largely realistic in content and plot (in the sense that they reproduce typical waking situations and capacities), may show aspects of bizarreness that can be assimilated to a mild clinical delirium, namely: visual intrusion (e.g., visual transformations of form and setting) and Sleep and Hypnosis, 5:3, 2003

cognitive confusion (e.g., deficiencies in memory and reasoning). Vice versa, dreams of Freud’s and Jung’s collections were characteristically bizarre. This approach does not consider bizarreness an invariant property of dreaming. Bizarreness is of great importance as an evidence of creative symbolic imagination (visualspatial processes) and has a metaphorical significance. In Hunt's view, dream bizarreness should be interpreted from several different levels of analysis and not from a merely physiological standpoint. PART II: MEASUREMENTS At the beginning of the 1960s a few authors attempted to measure the frequency of bizarre elements in dream contents by means of objective indicators. Retrospectively, we can see now that the terminology used by these scales of contents was influenced by the then prevailing theories. The measurement created in the 60’s and 70’s used terms like “distortion”, “metamorphosis”, “primary process thinking”, reflecting psychoanalytic concepts (e.g., “censorship”, “dream-work”, etc.). On the other hand, after the development of neurobiological and cognitive approaches, terms such as “discontinuities”, or “improbable combinations”, was clearly influenced by concepts like “random activity in the memory system” or “cognitive deficits” etc. The various scales of bizarreness may be categorized as follows: • general scales: these provide a qualitative ranking of general classes of bizarreness (e.g., discontinuity, incongruity, etc.) (see Table 2); • analytical scales: these provide a qualitative ranking of more specific kinds of bizarreness previously defined by the author (e.g., “changes in sex and identity”, “monsters”, etc.) (see Table 3); • global scales: these rank dreams using ordinal scales (e.g., various types of bizarreness are considered together without distinction in order to assign a 109

Dream Bizarreness Reconsidered

Table 2. Bizarreness - “General” content scales

110

Scale Name

Authors

Brief Description

Scoring Reactive Content

Rychlak & Brams (1963) (3)

This scale scores the unusual content compared to common expectation. Five categories: location, actors, action, mood terms, implements.

Salience

Cohen ’s study (as quoted in Winget & Kramer, 1979) (45)

Salience is defined by 8 scales. Bizarreness is one of these. Dreamer scores bizarreness as follows: settings (objects, space) and events (behavior, experiences) may be, 0-realistic likely, 1-unlikely, unexpected, but possible, 2-impossible, ridiculous.

Discontinuities. Improbable combinations. Improbable identities

Reinsel et al. (1992) (39)

Discontinuities: when a part of mentation is inconsistent with other parts according to common daily experiences; Improbable combinations (e.g. winged men); Improbable identities (e.g. impossible or changing identities).

Classificationratingsystem of formal anomalies

Hunt (1982) (43)

Dimensions/changes: a. Competence functions, b. performance (e.g. reasoning,memory attention), c. State of consciousness, d. Interpersonal relation and personality identity. These dimensions are divided into three stages: 1. Hypersensitivity to “ordinary” subjective aspects of experience. 2. Changes in awareness (e.g. derealization). 3. Specific anomalies in each dimension.

Dream bizarreness

Hobson et al. (1987) (27) Hobson (1988) (7)

Two-stage scoring system. Stage 1 identifies items as bizarre if they are physically impossible or improbable (e.g. plot, characters, thoughts of dreamer, etc.); Stage 2 characterizes items as showing discontinuity, inconsistency or uncertainty.

Bizarre contents

Cipolli, Bolzani, Cornoldi, De Beni, and Fagioli (1993) (46)

Bizarreness is defined according to the following criteria: a. physical impossibility, b. physical implausibility c. behavioral implausibility, d. functional implausibility and e. incongruity of dialogue, thought and feeling with respect to the situation.

Continuity and discontinuity

Sutton, Rittenhouse, PaceSchott, Stickgold, and Hobson (1994) (47)

This scale attempts to measure continuity and discontinuity in visual attention using the graphs theory. The sequence and developments of narrative reports are presented in hierarchy graphs. Discontinuities in temporal order are quantified by imposing a weighted value to each transition within the graph.

Discontinuities

Rittenhouse, Stickgold, and Hobson (1994) (48)

This scale analyzes the "mode" of discontinuities in settings, character and object. For example, we can observe the "Insertion" (sudden appearance) or "Removal" (sudden disappearance) of an object and character or "Shift" (initial) or "Return" (subsequent) in setting and plot.

Content Bizarreness Scoring

Revonsuo & Salmivalli (1995) (49)

Dreams are classified into a two-stage scoring: 1. Element identification (14 categories, e.g. self, actions, emotions) and 2. Content bizarreness scoring: A. Non-bizarre element (consistent with waking reality), B. Incongruous element (e.g. impossible in waking reality), C. Vague element, D. Discontinuous element.

Bizarreness

Colace & Natale (1997) (50)

This scoring scale classifies bizarreness as follows: 1) Bizarre Elements (4 types), a. Improbable or impossible characters, b. metamorphoses, c. improbable or impossible actions/inappropriate roles d. improbable or impossible objects; 2) Script bizarreness (4 types): a. improbable or impossible (physical) plot, b. improbable or impossible (logical) plot, c. plot discontinuity, d. improbable or impossible settings.

Bizarreness

Bosinelli (1999) (51)

Bizarreness is classified as: a. improbability, b. oddity or a+b. c. physical impossibility, d. logical impossibility or c+d.

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Table 3. Bizarreness - “Analytical” content scales Scale Name

Authors

Brief Description

Bizarre Elements

Domhoff & Kamiya (1964) (1)

This scale identifies 3 general classes of bizarre elements: metamorphoses (4 categories), unusual acts (2 categories), magical occurrences (4 categories).

Distortion from reality

Sutcliffe, Perry, & Sheehan, (1970) (52)

This scale scores atypical aspects with respect to the common experience occurring in real world. Samples of distortion considered are: changes in sex and identity, false belief, implausible behavior of an agent, alteration of typical appearances or dimension of an agent, etc.

Setting and characters distortion

Hall & Van de Castle (1966) (53)

Metamorphoses of characters: changes in sex, identity, or age. Changes from human into animal or vice-versa. Setting distortion: familiar settings indicated by the dreamer have an element of peculiarity or incongruity insofar as they differ from the way the dreamer knows the setting to be in his waking life.

Dream Bizarreness

McCarley & Hoffman (1981) (54)

Dream bizarreness is divided into three major groups: a. animate characters, 6 kinds (e.g. monsters, alien beings), b. inanimate environment, 3 kinds (e.g. violation of physical laws), c. dream transformations, 4 kinds (e.g. scene shift).

global score) (see Table 4); These three types of scales measure the quantity of dream bizarreness in different ways: while general and analytical scales score the frequency of bizarreness of dream reports in single units or elements (e.g., action or setting), global scales frequently score dream bizarreness by considering the dream as a whole. A common problem associated with many measurements is that some bizarre elements may be estimated differently without the help of the dreamer’s own judgments (e.g., improbability and implausibility in the light of their own personal waking reality) (49, 60). For example, Zepelin (60) compared the dreamer’s and the judge’s bizarreness ratings and concluded that the lack of knowledge about the dreamer’s waking experiences may lead the judge to exaggerate his/her rating of bizarreness. Future research should specify whether the bizarreness scale adopted includes the dreamer’s contribution or not1.

PART III: EMPIRICAL DATA AND IMPLICATIONS A. Frequencies Bizarreness in REM dreams Several studies have attempted to report the frequency of bizarre REM dreams; however, due to the different scales used, the conclusions reached were conflicting. Most of these studies agree in that bizarre dreams are very frequent, about 74% of REM dream reports (46,50,54, 60,62-67) (see Table 5 and 6). Less frequently, certain authors have suggested that there are notably lower percentages of bizarre REM dreams; however, they generally used a different definition of bizarreness (see Table 5) (3233). For example, in Snyder's study, an element being "extremely unlikely from the standpoint of waking reality" and yet conceivable is not evaluated as bizarre (p.146). Dorus et al. (33), who found little bizarreness in REM dreaming, used a content scale substantially different from

For the definitions and scales of bizarreness see also Hobson et al. (27) and, Bonato, Moffitt, Hoffmann, Cuddy & Wimmer (61).

1

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111

Dream Bizarreness Reconsidered Table 4. Bizarreness - “Global” content scales

112

Scale Name

Authors

Brief Description

Distortion

Foulkes & Rechtschaffen’s study (as quoted in Winget & Kramer, 1979) (45)

Distortion is measured as follows: 1 extremely distorted , 2 quite distorted, 3 fairly distorted, 4 somewhat distorted, 5 slightly distorted, 6 not distorted at all.

Dream ratings (bizarreness)

Gooudenough, Lewis, Shapiro, and Sleser’s study (as cited in Winget & Kramer 1979) (45)

A three-point scale of bizarreness/ rationality: 1= “most bizarre” (e.g. strange objects or events), 1/ = unusual elements or confused combinations of 2 ordinary elements, 0 = dreams with ordinary elements.

Regressive dream content

Vogel, Foulkes, & Trosman’s study (as quoted in Winget & Kramer, 1979) (45)

This scale classifies dreams as follows:Nonregressive content dreams = plausible, realistic, consistent and undistorted dreams. Regressive content dreams = 1 or more bizarre categories such as, bizarre sequence of images, inappropriate or distorted images, magical omnipotent thinking, etc.

Child rating scales Foulkes, Pivik, Steadman, / distortion Spear, & Symonds (1967) (55)

Dreams are classified into four levels: level 0 – no distortion (realistic recreation or anticipation of upcoming event), 1- no distortion (plausible and very probable event), 2- slight distortion (plausible but not probable), 3- considerable distortion (content is neither plausible nor probable but contains certain elements of reality) 4- major elements are neither plausible nor probable.

Scoring dream dimensions

Koulack’s study (as quoted in Winget & Kramer, 1979) (45)

Dream bizarreness: this scale refers to the extent of “unreality”. 1. Dream which is entirely true to life. 2. Dream containing both real and unreal elements. 3. Dream which is totally unreal.

Vivid fantasy

Weisz and Foulkes (1970) (56)

This scale measures the feeling of unreality (i.e., imagination and distortion) coupled with intensity of experience (dramatization) (A 5 - point scale).

Primary process thinking

Auld, Goldenberg, & Weiss (1968) (57)

Starting from the psychoanalytic concept of primary process, the authors focus on evaluating the “mode of thinking”. A 7- point scale: 1) logical vs. 7) bizarre and illogical thought.

Classification of novelty in dreams

Dorus, Dorus, & Rechtschaffen (1971) (33)

This scale measures the novelty of elements (e.g. setting, objects etc.) with respect to the experience of each dreamer. 1. the dream element is an exact replication of something previously experienced vs. 6. the dream element was not previously experienced and it is extremely unlikely that such an element could occur in the dreamer’s experience

Chicago sleep mentation scales

Rechtschaffen, Watson, Wincor, and Molinari’s study (as quoted in Winget & Kramer, 1979) (45)

The experimenter asks: How unfamiliar, strange, or distorted was the very last experience in terms of your waking experience? 1. almost exactly like my waking experience vs 6. new and unfamiliar and very unlikely to occur in my waking life.

Implausibility

Breger, Hunter, & Lane’s study (as quoted in Winget & Kramer, 1979) (45)

This scale classifies dreams as follows: 1- quite plausible (something that could well happen to the dreamer) vs. 5-bizarre (something that is so extremely unreal or fantastic that would be unusual even in a dream report).

Dream distortion

Zepelin’s study (as quoted in Winget & Kramer, 1979) (45)

This scale measures the strangeness of dream contents compared to waking experience. Level 0 = the event of dream closely resembles recent waking experience vs level 5 = major aspects of the dream are impossible (i.e. combination of illogical or improbable elements).

Distortion/ Bizarreness

Colace, Violani & Solano (1993) (58) Colace & Tuci (1996) (59)

The authors attempt to formalize the original classification of dream bizarreness in Freud’s view. Dreams are classified as follows: 1 = “sensible, plausible and without strange elements”, 2 = “sensible, consistent in themselves but odd compared to common life”, 3 = “senseless, inconsistent and bizarre”. Sleep and Hypnosis, 5:3, 2003

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Table 5. Percentages of bizarre dreams in REM sleep Studies

No of Dreams

Bizarre REM Dreams

McCarley & Hoffman (1981) (54)

104

67 %

reports containing at least one element of bizarreness (e.g. monsters, scene shift)1

Zepelin (1989) (60)

322

91 %

reports containing at least a number of elements not true to life (scores: “perfectly true to life” vs. “not at all true” (ratings 1-6)

Zito, Cicogna & Cavallero (1992) (67)

183

63 %

reports containing at least one bizarre element (physical and/or logical impossibility, or improbability (according to dreamer’s experience)

Cicogna, Cavallero & Bosinelli (1991) (63)

27

67 %

reports were scored as “plausible” or “implausible” according to waking standards.

Cavallero et al. (1992) (62)

50

66%

reports were scored as “plausible” or “implausible” according to waking standards.

Cipolli et al. (1993) (46)

110

79 %

reports containing bizarre elements (e.g. physical impossibility, behavioral implausibility, etc.)

Colace & Natale (1997) (50)

50

82 %

reports containing at least one bizarre feature (e.g. improbable or impossible characters, actions, roles, etc.)

Cicogna et al (1998) (64)

1442

84 %

reports were scored as “plausible” or “implausible”

Cicogna et al (2000) (65)

20

75 %

reports containing one or more impossible or improbable elements according to the subject’s waking experience

Natale & Esposito (2001) (66)

342

70 %3

reports containing one or more impossible or improbable elements according to the subject’s waking experience

Snyder (1970) (32)

635

L: 20-35% M: 5-15% H: 2-7%4

Dorus et al. (1971) (33)

119

16 %

Measurement

very improbable elements with respect to waking reality but yet conceivable are not necessarily evaluated as bizarre dreams with elements that are a replication of something previously experienced, but with major changes from the original (level 3 of 6)5

See table 3 for detail So, St 2, REM. Average score REM 1, 2, 3, 4, cicle 4 L = Low, M = medium and H = high bizarreness 5 See table 4 for detail 1 2 3

more common bizarreness scales (see Tables 2-4). From a theoretical point of view, these data are not consistent with the hypothesis that REM dreams are generally realistic compared to dreams derived from a psychoanalytic setting or from a home setting (70). Actually, as stated above, REM dreaming often reveals bizarre features. On the other hand, it may be observed that Sleep and Hypnosis, 5:3, 2003

dream bizarreness is not an invariant formal property of all dreams. About 25% of REM dreams among adults are not at all bizarre. In addition, non-bizarre dreams occur very frequently in young children (see below). The non-invariant nature of bizarreness in REM dreams cannot be easily explained through approaches that regard bizarreness as intrinsic to the neurobiology of REM sleep (7,15). 113

Dream Bizarreness Reconsidered

Table 6. Percentages of bizarre dreams across sleep stages Sleep Stages

Bizarre Dreams / Range

Average

Sleep onset

min 33% - 43% max

38 %

Cicogna, Cavallero & Bosinelli (1991) (63); Cicogna et al (1998) (64); Zito, Cicogna & Cavallero (1992) (67); Cicogna et al. (1996) (68).

NREM, stage 2

47% - 79 %

61 %

Cicogna, Cavallero & Bosinelli (1991) (63); Cicogna et al (1998) (64); Natale & Esposito (2001) (66); M.Bosinelli (personal communication).

NREM, stages 3-4 and 4

48% - 54%

51 %

Cavallero et al. (1992) (62); Cicogna et al. (2000) (65); Colace & Natale (1997) (50); M. Bosinelli (personal communication); Natale (2000) (69).

REM

63% - 91%

74 %

Cipolli et al. (1993) (46); Colace & Natale (1997) (50); McCarley & Hoffman, (1981) (54); Zepelin, (1989) (60); Zito et al. (1992) (67); Cicogna, Cavallero & Bosinelli (1991) (63); Cavallero et al. (1992) (62); Cicogna et al (1998) (64); Cicogna et al. (2000) (65); Natale & Esposito (2001) (66).

support the hypothesis that the underlying cognitive processes of dream production mechanisms could be the same through all sleep stages. However this dream-generation system may be associated to the quantity of mnestic activation that is different between REM and NREM sleep (i.e., different levels of system engagement) (85);

Comparing bizarreness in REM and NREM dreams Empirical evidence suggests that the original “REM sleep=dreaming” hypothesis and the rigid REM/NREM dichotomy needs to be completely revised. In particular, researchers have found that2: • REM sleep, in itself is not a sufficient condition for dreaming. Foulkes has demonstrated that in children aged 3 to 5 REM dreaming is relatively absent; i.e. the presence of REM sleep is not a guarantee of concomitant dream activity (34-35,73); • REM sleep is not a necessary condition for dream production. Several studies have shown that dreams can occur during all the sleep stages (6,62,63,67,70,74-83). In particular, the work of the research group of the Sleep and Dream Laboratory of the Bologna University Department of Psychology has shown that dream-like mental activity is present also in slow wave sleep (SWS) (from a physiological point of view this sleep phase differs greatly from the REM phase) (65,66,69,72,84). These studies

STUDIES

• In agreement with the above, Solms’neuropsychological studies suggest that REM sleep and dreaming are dissociable states, controlled by different brain mechanisms (86-88). Thus, dreaming is preserved even when a major damage to pontine brainstem eliminate REM sleep. Therefore, dream mentation can occur without REM sleep. Furthermore, forebrain damage (dopamine circuit) would stop dreaming but would not affect REM sleep. Consequently, dreaming can be initiated by the forebrain mechanisms regardless of REM state. These results open the field to investigations on bizarreness in NREM dreaming as well. As a further analysis of dream bizarreness the following two

On the REM//NREM current debate see Nielsen (71) and Cavallero (72)

2

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questions should be answered to: 1. Is bizarreness an exclusive feature of REM dreaming? 2. Are REM dreams characteristically (qualitatively and quantitatively) more bizarre than NREM dreams? The data found in literature demonstrate that bizarreness is not exclusive to REM dreaming, as bizarre dreams are frequently present in NREM sleep. In particular, the percentage of bizarre dreams is about 38% in sleep onset, about 61% in NREM stage 2, and about 51% in stages 3 and 4 (SWS) (see Table 6). These results suggests that bizarre mentation is not state-specific of REM sleep, and its distinctive neurobiological events (PGO activity and aminergic demodulation), are not a necessary condition for bizarre dreaming. It could be hypothesized that there are other causes of bizarreness, different from the ones assumed in REM sleep. Thus, the models that base their explanation of bizarreness on REM neurobiological events do not account exhaustively for the explanation of dream bizarreness in other phases of sleep. The followings studies have compared directly the frequency of bizarre dreams in REM and NREM sleep and might contribute to providing an answer to the second question. REM vs. sleep onset. Several studies underlined the low frequency of bizarre dreams in sleep onset stage compared to REM sleep (63,64,67,76,82,89-91). A few authors have suggested that the contents of mentation at sleep onset are still strongly related to the waking state, which supposedly limits the presence of bizarreness (66,78). REM vs. NREM, Stage 2. The studies that have compared dream reports for bizarreness in REM and NREM stage 2 are controversial, and certain methodological aspects should be viewed in deeper detail before interpreting their results. • Measurements. The differences found between REM and NREM Stage 2 dreams depend much on the Sleep and Hypnosis, 5:3, 2003

measurement used for bizarreness. For example, by applying “global” (ordinal) bizarreness scales the REM dreams observed are more bizarre than NREM dreams, while “general” (qualitative) scales applied to the same dream reports do not lead to the same results (39,92). • Correlation between length and bizarreness of dream reports. The wellknown correlation between the length of dream reports and their bizarreness (36,54,57,93) may make the differences between REM and NREM dreams bizarreness scores less clear (REM dreams are frequently longer). Thus, the difference between REM and NREM stage 2 dream reports vary according to whether dream length is controlled or not (39). In general, authors suggesting that REM–NREM mentation differ only in quantitative terms but not qualitatively (i.e., the mechanisms of dream production are the same across sleep stages) usually compare REM and NREM dreams after dream report length is controlled and find no difference (39,66,69). These authors suggest that the heightened frequency of bizarreness in REM dreams is the result of the increased cortical activation (memory systems included) found in REM sleep (36,81). In other words, they suppose that REM dreams are longer and more bizarre because the underlying cognitive processes operate on higher levels of engagement than in NREM stage 2 sleep conditions. On the other hand, authors claiming that the correlation between bizarreness and length does not justify the differences between in REM and NREM dream bizarreness, (wrongly assumed only in quantitative terms), maintain that the difference remains even when length is controlled, hence REM dreams are always more bizarre than NREM, stage 2, (12,92,94). These authors have interpreted these results in support of the activation-synthesis model. The studies that analyzed REM vs. NREM stage 2 differences in dream 115

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bizarreness are still numerically insufficient in order to draw any sort of general conclusions. The evidence that emerges from previous studies is insufficient to conclude that REM dreams are more bizarreness than NREM stage 2 dreams. REM vs. NREM, stages 3 and 4. Very few studies have compared REM and Stage 3 and 4 sleep mentation for bizarreness scores. Cavallero et al. (62) used a measurement of Plausibility/Implausibility and found no significant differences in the frequency of “plausible” dreams between REM and SWS sleep (slow wave sleep). Colace and Natale (50) compared REM and SWS sleep mentation (Dreams Data Bank, Bologna University, Department of Psychology, 95) and found that REM dream reports were significantly more bizarre than SWS dream reports for “script bizarreness”, but no significant differences were found when looking at “bizarre elements” (see Table 2 for detail). It is interesting to note that when dream length was controlled, all REM/SWS differences disappeared. Recently, Cicogna et al. (65) found no significant differences in “implausibility” (one or more impossible or improbable elements) between REM and SWS mentation. Although the comparison between REM and Stage 3-4 sleep mentation should be examined more closely, the data available seem to point to the conclusion that there are not significant differences in bizarreness between these two stages. In conclusion, previous researches have found no clear differences in bizarreness between REM and NREM dreaming (with the exception of sleep onset dreaming). There is not enough evidence to support the hypothesis that REM dreaming is typically more bizarre than NREM dreaming. The methodological issues of the uniformity of the measures used, and of whether it is appropriate or not to correct report length are still open in comparative analyses between REM and NREM dreaming (96). Bizarreness: dreams vs. waking mentation The studies on bizarreness in relaxed 116

wakeful mentation may contribute to clarify whether bizarreness is exclusive to dreaming or not, and whether REM dreams are typically more bizarre than waking mentation (i.e. relaxed wakefulness, "simulated dreams," daydreaming). The findings in literature reveal that bizarreness is also undoubtedly present in relaxed wakeful mentation (97-99). Furthermore, other studies have found that relaxed wakeful mentation and "simulated dreams” are equally–or perhaps even more–bizarre than REM dream reports (39,100). For example, Reinsel et al. (39) compared REM dreams, NREM stage 2 dreams, and relaxed wakeful mentation (subjects were reclining in a darkened room) and found that there is a greater quantity of bizarreness in waking thoughts. The authors suggested that these results were consistent with the GCAT model, according to which the higher cortical activation level during waking state (compared to REM and NREM sleep) might increase bizarre contents. The studies based on “home dreaming” led to controversial results. Williams et al. (99) compared “home dreaming” reports to waking fantasies and showed that home dreams were significantly more bizarre. The authors claimed that their results were consistent with the “activation synthesis” hypothesis. Subsequently, Strauch & Lederborgen (101) obtained comparable results. On the other hand, Carswell and Webb (102) compared home dreams and “artificial dream reports” (i.e., subjectdeveloped summaries of a random succession of photographs) and found no difference in the rates of “implausibility” and bizarreness used (“unusual acts” and “magical occurrence”). The only category found to be more frequent in home dreams was the “metamorphosis”. Since studies have revealed that there were at least no significant differences between REM dream reports and waking mentation, the great quantity of bizarreness found in home dreams by certain authors could be due to the effects of a better recall of bizarre elements after a longer time span since dream generation (46). It is clear, from the Sleep and Hypnosis, 5:3, 2003

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studies reviewed, that there is no distinctive physiological property of REM sleep that can explain bizarreness alone, because bizarreness also occur in waking mentation and because REM dreams do not seem to be characteristically more bizarre than waking fantasies. Vice versa, these results are more consistent with those models that assume qualitatively common processes during dreams and waking fantasies. B. Neurophysiological and neurobiological factors Phasic events Several authors have focused on the phasic events of REM and NREM sleep and on the parallel presence of bizarre elements in dream contents (103-105). Bizarreness seems to be related to REMs (Rapid eye movements) (106), with PIPs (Periorbital Integrated Potentials, the equivalent of PGO in humans) in REM and NREM sleep (107-109) and with MEMA (middle-ear muscle activity) in REM and NREM sleep (110). However these data were not always confirmed (111). While there is no evidence supporting that PGO spikes are a necessary cause of bizarreness (see below) the possibility remains that, phasic neural events (intrusion), in general and not only at PGO level, during REM and NREM sleep may provide one source (i.e., correlate) of bizarre mentation. PGO activity The hypothesis that dream bizarreness may be attributed to the nature of pontine PGO activity suggests that dream bizarreness imagery might be due to: a) non-cognitive (subcortical) and random nature of eye movements and their associated PGO spikes, and b) from the fact that dreaming and dream bizarreness could consist of associations and memory units elicited from the forebrain in response to random inputs from the brainstem (PGO) (i.e., random processing in memory system). Unfortunately, several

data do not support this hypothesis: • bizarreness is also present in NREM dreams where PGO activity is notably reduced (39); • there are insufficient data to support the concept of random and non-cognitive nature of pontine brainstem activation. In fact the beginning of eye movement (EM), its associated PGO activity, and the resulting dream imagery might not be totally independent from the prior cortical/cognitive activity. In other words, the cortex may have an important role in initiating and creating the visual imagery of dreaming. (38,112-116)3; • Solms (88) suggested that dream imagery is not generated by the brainstem’s chaotic activation of the forebrain–on the contrary, it is apparently built through complex cognitive processes; • various studies have shown that dreams are meaningful rather than random events. In particular, dream contents are affected by gender, age, social status and psychopatology (118-119,45). • the data from studies on memory consolidation during REM sleep clash with the hypothesis of random processing in memory system. Pavlides and Winson (120-121) in an singleunit experiment with rats found that hippocampal neurons (CA1 “place cell”), that had fired preferably in their place fields during waking state, in order to encode spatial information and committing it to memory, fired preferably in subsequent sleep states (REM/SWS). This result was replicated in another study with three rats (122). Similarly, Skaggs and McNaughton (123) found that the pattern of rat hippocampal pyramidal cells during sleep reflects the order in which the cells fired during earlier spatial exploration in a waking state. These data imply the existence of a sort of orderly processing of the memory

On this topic see also Mancia (117)

3

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rather than a random activity during sleep. In particular, Winson suggest that in REM sleep types of memory that are important for survival information during waking state are selectively and preferentially reprocessed (122,124). This group of data is not consistent with the models according to which PGO random activation and its supposed consequences in the memory system are the cause of bizarreness. Specifically, these studies show that PGO activity is neither a necessary nor a sufficient condition of dream bizarreness. More generally, these data clash with the concept of dreams as a chaotic and random product. Aminergic demodulation In Hobson’s view, the aminergic demodulation of the brain in REM sleep could be a cause of cognitive deficits that contribute to dream bizarreness, compared to waking state where aminergic neuromodulation is high (12,14,125). For example, aminergic demodulation might predict an alteration in the strength of associative links in memory (i.e., hyperassociative character) that would explain the bizarre character of REM dreaming (126). Recently this view has been suggested also by Gottesman (127128) who claimed that the aminergic demodulation in REM sleep (with the exception of dopaminergic neurons) could be responsible for unusual cognitive functioning and for dream bizarreness. These hypotheses seem scarcely plausible, as long as we have seen that: a) bizarreness is also present in waking mentation and in NREM sleep, where aminergic modulation is supposed to be efficient (see above); b) recent studies suggest that certain cognitive abilities, e.g. attentional processes, are not impaired during dreaming compared to waking (129-131); c) while, according to the “aminergic demodulation hyphotesis”, bizarreness should be a constant formal property of all 118

dreams, it has been found that young children’s dreams are not bizarre at all (see below); On grounds of the above, aminergic demodulation is neither a necessary nor a sufficient condition for dream bizarreness. Dorsolateral prefrontal cortex inactivity Studies on dreaming with Positron Emission Tomography (PET) show which parts of the brain areas are active and which are inactive during REM sleep. With this method, some authors have hypothesized that the deactivation of the dorsolateral pre-frontal cortex during REM sleep, which causes cognitive deficits (e.g., short-term memory, orientation, etc.), would explain why dreams are so bizarre and illogical (12, 23,127,132-136). These approaches to the explanation of REM dream bizarreness are inclined to considering bizarreness as a constant formal property; however, we have seen that this is not true. Cortical/cognitive activation The hypothesis of Antrobus et al. (3839,112), i.e. bizarreness is due to an overall increase in cortical and cognitive activation, appears to be backed by the following data: a) Individuals with high cortical activation in NREM sleep have shown a greater amount of “dreaming” while individuals with slow cortical activation showed NREM mentation defined as “thought-like” (42); b) Dream reports of the second half of night sleep (where it is supposed to be a greater cortical/cognitive activation) are generally more bizarre than in the first part (66,70,94,114,137-139); c) Waking and REM mentation (states with higher activation), if report length is not controlled, may appear more bizarre than NREM stage 2 mentation (39). Based on these data, the bizarreness of REM dreaming could reflect persistent cortical activation rather than specific Sleep and Hypnosis, 5:3, 2003

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mechanism of REM sleep. Frontal-limbic structures Based on clinic/anatomical studies, Solms (86,88) hypothesized that the frontal–limbic structures (anterior cingulate gyrus, anterior and dorsomedial thalamus, basal forebrain nuclei, and medial frontal cortex) would be implicated in Freud’s “censorship” function. In fact this region seems essential for the control and regulation of emotions and impulses, and for the reality monitoring system through the inhibition of the motor system during sleep. When this region is functioning normally, arousal stimuli of dream processes are deflected towards the perceptive system (i.e., dream-work, symbolic operation etc.); conversely, when this region is damaged excessively frequent and intense dreaming is triggered. C. Individual factors Age Various studies have shown that dreams of normal children of preschool age are often simple rather than bizarre, even if collected with different methodologies (family/nonfamily interviewer) and/or in different settings (dream laboratory, home, school) (34,58,59,140-145). The frequency of nonbizarre dreams is about 70%. These data confirm previous anecdotal and quantitative observation on the simplicity of children’s dreams (146-148). Bizarreness seems to occur more frequently starting from 5 to 6 years of age compared to dreams of younger children (34,58,142,149). These data suggest that dream bizarreness should not be considered as an intrinsic regular property of the dream process. Indeed, in the light of children’s dreams, it’s difficult to ascribe dream bizarreness to a unique neurobiological condition. In particular, why do random PGO activity and aminergic demodulation not cause bizarre features in children’s dreams? Hobson’s colleagues also found that children’s dreams are not bizarre, but, Sleep and Hypnosis, 5:3, 2003

quite surprisingly, no implications of this finding were elaborated for their own theory of dream bizarreness (12,145). Finally, some preliminary systematic observations in young children’s dreams show that they are frequently a clear and easily understandable wish-fulfillment (142,150). From this point of view, dreams cannot be characterized as meaningless, the result of random nerve cell activity (7) or as a mere activity aimed at reducing spurious associations, fantasy and obsession (15). Studies on formal aspect of children dreams are fully consistent with the psychoanalytic approach. Personality development The psychoanalytic model predicts that children dreams are not bizarre because they have not yet developed the superego function that could permit the defensive transformation of latent dream contents (17,19-22). Certain studies have found indications consistent with this hypothesis. For example, Foulkes (34) has shown that dream “distortion” is correlated to “social comprehension” scores (Wechsler Test) (i.e., development of moral norms, adjustment to reality). Colace et al. (58,141,142) suggest that the appearance of bizarreness in children’s dreams seems more related to measures of the “capacity to experience guilt feelings” (i.e., differentiation of the super- ego function, interiorization of moral norms) than to descriptive/linguistic abilities. Furthermore, in agreement with Foulkes’ findings, these authors found that in children of 3-6 years of age “social comprehension” is correlated to scores of the “capacity to experience guilt feelings” and that both these variables are positively correlated with measures of dream bizarreness (142). Waking creativity Several empirical studies have strongly supported the hypothesis of a positive relationship between dream bizarreness and waking creativity (151-157). In a critical review of these studies, Wood, Sebba and Domino (93) suggested that dream 119

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bizarreness might be primarily related to vocabulary knowledge than to waking creativity. According to Wood, Sebba and Domino, the dream reports of verbally intelligent people obtain higher bizarreness ratings only because they are longer, and not because they contain a higher “density” of bizarre events. A similar result was found by Livingston and Levin (158). However, at least three facts should be mentioned in opposition to these statements: a) people with higher verbal creativity do not always have longer dreams (159), b) several studies have found that non-verbal measures of imaginative ability rather than verbal ability are excellent predictors of dream bizarreness (160-164), c) certain authors suggest and maintain that, in observing the relationship between bizarreness and creativity, to separate dream length from bizarreness may be a questionable practice (43,96,164). In accordance with these data, Hartmann’s group found that individuals with “thin boundaries” property (i.e., flexible, imaginative and creative individuals) report more bizarre dreams than people with “thick boundaries” property (i.e., solid, rigid and reliable individuals) (165-169). Psychopathology indices Several studies have given good support to the relationship between dream bizarreness ratings and the degree of psychological disturbance of the dreamer measured with the MMPI test (total score and/or scale of “hysteria” and Sc) (2,3,171). Other studies have observed that the dreams of schizophrenic patients generally appear more bizarre (oddity, implausibility) than those of normal individuals (170,172-174). In addition, the dreams of the schizophrenic are frequently characterised as unrealistic (175-180). Carrington (170) compared the dream reports of schizophrenic and nonschizophrenic individuals and showed that the dreams of the former were more bizarre than those of control subjects. Furthermore, in the control group, dream 120

bizarreness was associated with welladjusted/maladjusted (MMPI) scores. Carrington concluded that a high rate of dream bizarreness might, on the basis of further investigation, turn out to be at least an important index of the degree of maladjustment in the dreamer. It is also worth noting that dreams are more unrealistic among children suffering from emotional disturbances (55). These results are consistent with the psychoanalytic view according to which the dreams of maladjusted persons are generally more bizarre (quantitatively) than those of normal persons (18). The results of studies on waking creativity and psychopathology converge together towards the following statements: • NREM PIPs activity (correlate of bizarreness), that vary from one individual to another, is more frequent in psychiatric patients and in individuals who show a greater imagination (correlates with dream bizarreness) (181-184); • NREM PIPs activity seems more frequent in persons who have less control of overanxiety, fluid ego boundaries, less solid sense of self , and with more imagination (i.e., “thin boundaries” structure) rather than in persons with better control of anxiety, rigid ego boundaries and less imagination (i.e., “thick boundaries” structure) (182). We have seen that “thin” persons are exactly those who dream a greater number of bizarre dreams (see above). The data on the relationship between dream bizarreness and waking creativity, psychopathology degree, and types of ego boundaries structure, suggest that dream bizarreness is substantially and not negligibly affected by individual differences. All those models that ascribe dream bizarreness solely to neurobiological events cannot explain the effects of individual differences (Hobson, Crick and Mitchison) or at least do not explain how can these variables reconcile Sleep and Hypnosis, 5:3, 2003

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with a neurobiological explanation. CONCLUSIONS The activation-synthesis hypothesis and its updated versions, that attribute dream bizarreness solely to the distinctive neurobiological conditions of REM sleep, can be essentially rejected on the basis of the data found in literature. This approach suggests that dream bizarreness is a constant formal property of all dreams because it is intrinsic to REM sleep neurobiology, namely PGO random activity and aminergic brain demodulation. Moreover, as these neurobiological events are not present in NREM dreaming and in waking mentation, bizarreness is supposed to be exclusive and peculiar to REM dreaming. These assertions are not supported by data. Indeed there is evidence that dream bizarreness is a non-invariant, non-exclusive and not peculiar feature of REM dreaming. Particularly, although REM dreams are frequently bizarre in adults, there are also REM dreams that are not at all bizarre, and non-bizarre dreams have been often observed in young children. In practice, the neurobiological events of REM sleep are not a sufficient condition for the occurrence of bizarreness. The literature shows that bizarreness is present also in NREM dreaming and in some waking mentation (e.g., relaxed waking, fantasies, etc.). In addition, it cannot be clearly distinguished from REM dreaming bizarreness. In other words, the neurobiological events of REM sleep (PGO activity, aminergic demodulation) are not an essential requirement for bizarreness. Results from other researches have cast doubts on the role of PGO brainstem activation as a cause of REM dream bizarreness. Thus, the assumption that REM dream bizarreness may be attributed to the random and non-cognitive nature of PGO activity is not supported by the following data: in first place, dream imagery seems to be actively constructed through complex cognitive processes rather than generated by brainstem chaotic activation of the forebrain; secondly, experimental studies on Sleep and Hypnosis, 5:3, 2003

rat sleep suggest that during REM sleep the processes in the memory system are orderly, rather than random. Most of these data, conflicting with the “activation-synthesis” hypothesis, also question the two other neurobiological explanations of bizarreness, which are largely based on the concept of PGO activity and on the REM=dreaming equation (i.e., the “reverse learning” theory and Seligman and Yellen’s model). Apart from the evidence to the contrary at neurobiological level, there is another major reason for reconsidering the neurobiological approach to dream bizarreness: the data on the relationship between dream bizarreness and waking creativity, psychopathology and types of ego boundaries structure, suggest that dream bizarreness is substantially influenced by individual variables. From this viewpoint, the studies on children’s dreams have been quite useful in reconsidering dream bizarreness. In particular, they have shown that: (i) bizarreness is not present in early forms of dreaming, (ii) bizarreness seems to appear at around 5 to 6 year of age, and (iii) it seems to be related to the development of moral norms. While the literature data do not seem consistent with the activation-synthesis hypothesis and other neurobiological approaches, they appear to be at least in part consistent with other alternative theories on dream bizarreness. The non-invariant nature of bizarreness seems more consistent with models that do not regard bizarreness as intrinsic to dreaming processes. The presence of bizarreness in dreams in all sleep stages and in some waking mentation (e.g., fantasies) seems more consistent with the concept of a common dream generation system in the stages of sleep and of waking fantasies that is typical of cognitive approaches. On the other hand, Foulkes’s claim of an essential realism of REM dream reports does not seems to be confirmed. The evidence of more bizarreness in dream reports of the second half of night sleep than in those of the first part is 121

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consistent with the GCAT model on the role of cortical cognitive activation in the increase of dream bizarreness. While there is no evidence that PGO spikes are fundamental for bizarreness, there still is the possibility that, phasic neural events (intrusion), in general and not only PGO, during REM and NREM sleep may be a source (i.e., correlate) of bizarre mentation. From this viewpoint, Watson has shown that PIPs activity varies individually and is more frequent in psychiatric patients and in persons with greater imaginative abilities; exactly those people who apparently have more bizarre dreams. The data on the relationship between dream bizarreness and psychopathology are consistent with Hunt’s finding that dream reports in a psychoanalytic setting are more bizarre than home and laboratory dreams. Together, these data seem to confirm Freud‘s observation, i.e. that the dreams of neurotic patients were more bizarre than those of normal people. In addition, the studies on the formal aspect of children’s dreams are totally consistent with the psychoanalytic approach.

Briefly, the literature has highlighted a need to reconsider dream bizarreness in a more general way, including several levels of analysis (neurobiological, cognitive and psychological-motivational), rather than taking only the neurobiological point of view. Dream bizarreness cannot be explained as a simple expression of neurobiological facts, and, on the other hand, individual determinants seem to play an important role in its theoretical explanation. From this perspective, considering dream bizarreness as deprived of any psychological significance and dreams themselves as a meaningless byproduct appears to be premature. The studies on dream bizarreness could probably be supported by research work on those forms of dreaming which, for reason still unclear, do not show the presence of bizarreness (e.g., children dreams, childish adult dreams, etc.). On the other hand, the clinical/anatomical method, which has already proved to be useful somehow in the study of dreams, might also contribute to the research on the underlying factors of dream bizarreness production.

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