In lucid dreams the dreamer is aware of dreaming and often able to influence the ongoing dream content. Lucid dreaming is a learnable skill and a variety of techniques is suggested for lucid dreaming induction. This systematic review evaluated the evidence for the effectiveness of induction techniques. A comprehensive literature search was carried out in biomedical databases and specific resources. Thirty-five studies were included in the analysis , of which 26 employed cognitive techniques, 11 external stimulation and one drug application. (...) The methodological quality of the included studies was relatively low. None of the induction techniques were verified to induce lucid dreams reliably and consistently, although some of them look promising. On the basis of the reviewed studies, a taxonomy of lucid dream induction methods is presented. Several methodological issues are discussed and further directions for future studies are proposed. (shrink)

Empirical studies largely support the continuity hypothesis of dreaming. Despite of previous research efforts, the exact formulation of the continuity hypothesis remains vague. The present paper focuses on two aspects: the differential incorporation rate of different waking-life activities and the magnitude of which interindividual differences in waking-life activities are reflected in corresponding differences in dream content. Using a correlational design, a positive, non-zero correlation coefficient will support the continuity hypothesis. Although many researchers stress the importance of emotional involvement on the (...) incorporation rate of waking-life experiences into dreams, Hartmann formulated the hypothesis that highly focused cognitive processes such as reading, writing, etc. are rarely found in dreams due to the cholinergic activation of the brain during dreaming. The present findings based on dream diaries and the exact measurement of waking activities replicated two recent questionnaire studies. These findings indicate that it will be necessary to specify the continuity hypothesis more fully and include factors which modulate the incorporation rate of waking-life experiences into dreams. Whether the cholinergic state of the brain during REM sleep or other alterations of brain physiology are the underlying factors of the rare occurrence of highly focused cognitive processes in dreaming remains an open question. Although continuity between waking life and dreaming has been demonstrated, i.e., interindividual differences in the amount of time spent with specific waking-life activities are reflected in dream content, methodological issues have limited the capacity for detecting substantial relationships in all areas. Nevertheless, it might be concluded that the continuity hypothesis in its present general form is not valid and should be elaborated and tested in a more specific way. (shrink)

Even though various investigations found a preponderance of negative emotions in dreams, the conclusion that human dream life is, in general, negatively toned is limited by several methodological issues. The present study made use of three different approaches to measure dream emotions: dream intensity rated by the dreamer, intensity rated by a judge, and scoring of explicitly mentioned emotions (Hall & Van de Castle, 1966). Results indicate that only in the case of external raters' estimates do negative emotions outweigh the (...) positive ones; but in the case of self-ratings (i.e., those made by the dreamer himself/herself), the ratio was balanced. Analyses showed that this is mainly due to the underestimation of positive emotions in the external ratings. Additionally, a positive correlation was found between the intensity of dream emotions and dream recall frequency, whereas gender differences were nonsignificant as regards the emotional tone of diary dreams. (shrink)

Recent studies suggest that lucid dreaming might be associated with increased brain activity over frontal regions during rapid eye movement sleep. By applying transcranial direct current stimulation , we aimed to manipulate the activation of the dorsolateral prefrontal cortex during REM sleep to increase dream lucidity. Nineteen participants spent three consecutive nights in a sleep laboratory. On the second and third nights they randomly received either 1 mA tDCS for 10 min or sham stimulation during each REM period starting with (...) the second one. According to the participants’ self-ratings, tDCS over the DLPFC during REM sleep increased lucidity in dreams. The effects, however, were not strong and found only in frequent lucid dreamers. While this indicates some preliminary support for the involvement of the DLPFC in lucid dreaming, further research, controlling for indirect effects of stimulation and including other brain regions, is needed. (shrink)

Dreaming in patients with schizophrenia was and is of particular interest to researchers and clinicians due to the phenomenological similarities between the dreaming state and schizophrenic daytime symptomatology such as bizarre thoughts or hallucinations. Extensive literature reviews have shown that dream studies in the field of psychopathology often do not fulfill common scientific criteria. The present paper focuses on the methodological issues like sampling methods, the dream collection method, and dream content analysis that are crucial with regard to the validity (...) of the findings. It is also suggested that the so-called dimensional approach (linking severity of daytime symptoms directly to specific dream characteristics) will be very helpful for identifying which psychopathological symptoms of schizophrenia are most closely linked to dream content. (shrink)

Dream lucidity, or being aware that one is dreaming while dreaming, is not an all-or-none phenomenon. Often, subjects report being some variant of “a little lucid” as opposed to completely or not at all. As recent neuroimaging work begins to elucidate the neural underpinnings of lucid experience, understanding subtle phenomenological variation within lucid dreams is essential. Here, we focus on the variability of lucid experience by asking participants to report their awareness of the dream on a 5-point Likert scale. Participants (...) implemented a combination of mnemonic training lucid dream induction methods at home for one week and provided detailed reports about their dream experiences each morning. Consistent with previous research, cognitive induction methods led to about half of participants reporting at least one lucid dream and about half of all dreams including some level of lucidity. However, we also show that induction success rate varies significantly depending on the minimum criteria for lucidity. Participants also reported how much they adhered to specific components of each induction method, and the amount of mnemonic rehearsal during a brief early awake period was predictive of lucidity level. Furthermore, lucidity levels were positively correlated with dream control, dream bizarreness, and next-morning positive affect. Lastly, we asked participants open-ended questions about why they chose particular levels of lucidity. We focus a qualitative discussion on responses to those “semi-lucid” dreams to explore why participants rate their dreams as having intermediate levels of awareness. Together, the present study explores the frequency of semi-lucid dreams, what they are, why they might arise, their correlates, and how they impact methodological concerns in lucid dreaming research. (shrink)

All five target articles are of high quality and very stimulating for the field. Several factors such as dream report length and NREM/REM differences, may be affected by the waking process (transition from sleep to wakefulness) and the recall process. It is helpful to distinguish between a model for REM sleep regulation and a physiological model for dreaming. A third model accounting for cognitive activity (thought-like dreaming) can also be of value. The postulated adaptive function of dreaming in avoidance learning (...) does not seem very plausible because the two major basic assumptions (specificity of dream content and benefit of negative dreams) are not clearly supported by modern dream research: The critique of studies investigating memory consolidation in REM sleep is justified. Future studies integrating the knowledge of memory processes and sleep research will shed more light on the role of sleep, especially REM sleep in memory consolidation. [Hobson et al.; Nielsen; Revonsuo; Solms; Vertes & Eastman]. (shrink)

According to the continuity hypothesis of dreaming and contemporary psychodynamic approaches, dreams reflect waking life. The aim of the present study was to explore the relationship between the COVID-19 pandemic and dreaming in adolescents. A cross-sectional survey was conducted in Italy, Romania and Croatia involving 2,105 secondary school students. No substantial differences between countries were found. Thirty-one percent of the participants reported heightened dream recall, 18% noticed an increase in nightmares during the lockdown, and 15% of the provided dreams included (...) pandemic-related content. The results indicate that subjective emotional reactions to lockdown had a significantly higher correlation to dreaming than objective distress. These findings suggest that attention to dreams should be included in preventive programs for adolescents with pandemic-related stress. (shrink)

The coefficients of internal consistency and retest reliability had been rarely investigated within the methodology of dream content analysis. Analyzing a dream series of elderly, healthy persons obtained from weekly telephone interviews, the internal consistency of a series of 20 dreams and retests after 4 or 22 weeks, respectively, had been computed. The findings indicate that dream recall and dream length are quite stable, but dream characteristics such as bizarreness and emotional tone underlie large intraindividual fluctuations. In order to obtain (...) reliable measures for these variables which will be important for correlational studies, including waking-life trait measures, one has to obtain as many dreams as possible (about 20) in a very short time period. Further research is needed to extend the present findings to diary dreams and laboratory dreams. (shrink)

The coefficients of internal consistency and retest reliability had been rarely investigated within the methodology of dream content analysis. Analyzing a dream series of elderly, healthy persons obtained from weekly telephone interviews, the internal consistency of a series of 20 dreams and retests after 4 or 22 weeks, respectively, had been computed. The findings indicate that dream recall and dream length are quite stable, but dream characteristics such as bizarreness and emotional tone underlie large intraindividual fluctuations. In order to obtain (...) reliable measures for these variables which will be important for correlational studies, including waking-life trait measures, one has to obtain as many dreams as possible in a very short time period. Further research is needed to extend the present findings to diary dreams and laboratory dreams. (shrink)

In this commentary the “incredibly robust” evidence for the relationship between sleep and procedural memory is questioned; inconsistencies in the existing data are pointed out. In addition, some suggestions about extending research are made, for example, studying REM sleep augmentation or memory consolidation in patients with sleep disorders. Last, the possibility of a relationship between dreaming and memory processes is discussed.

Dream research shows sex differences in dream aggression that fit very well with the findings for waking-life aggressive behaviour. Dream studies are a valuable tool for investigating variables underlying the sex difference in aggression. One might argue that studying dream aggression might be even more promising because aggression in dreams is not socially labelled, as being aggressive in waking life is.

The hypothesis that dreaming is involved in off-line memory processing is difficult to test because major methodological issues have to be addressed, such as dream recall and the effect of remembered dreams on memory. It would be fruitful to study the dreams of persons who use AAOM regularly.