Forgetting of dreams in the laboratory

The effect of dream report collection and dream incorporation on memory consolidation during sleep

Collecting dream reports typically requires waking subjects up from their sleep—a method that has been used to study the relationship between dreams and memory consolidation. However, it is unclear whether these awakenings influence sleep‐associated memory consolidation processes. Furthermore, it is unclear how the incorporation of the learning task into dreams is related to memory consolidation. In this study we compared memory performance in a word–picture association learning task after a night with and without awakenings in 22 young and healthy participants. We then examined if the stimuli from the learning task are successfully incorporated into dreams, and if this incorporation is related to the task performance the next morning. We show that while the awakenings impaired both subjective and objective sleep quality, they did not affect sleep‐associated memory consolidation. When dreams were collected during the night by awakenings, memories of the learning task were successfully incorporated into dreams. When dreams were collected in the morning, no incorporations were detected. Task incorporation into non‐rapid eye movement sleep dreams, but not rapid eye movement sleep dreams positively predicted memory performance the next morning. We conclude that the method of awakenings to collect dream reports is suitable and necessary for dream and memory studies. Furthermore, our study suggests that dreams in non‐rapid eye movement rather than rapid eye movement sleep might be related to processes of memory consolidation during sleep.

Dream Recall: State or Trait Variable? Part I: Model, Theories, Methodology and Trait Factors

The aim of the present article is to carefully review the research carried out hitherto regarding factors influencing dream recall. With respect to the hypotheses explaining the variation in dream recall frequency (DRF) and a model of the dream recall process, the empirical data has been divided into two groups, trait factors and state factors. In the first part of the article the studies on the influence of trait factors are reviewed. The second part incudes data concerning state factors, new empirical data and some final conclusions. State factors such as nocturnal awakening and focusing on dreams in the morning and trait factors such as fantasy life, creativity and visual memory play a major role in explaining variability in dream recall.

Facilitating the Reportage of Dreams with Semantic Cues

Three experiments investigated dream reports from the previous night. The major hypothesis tested was that the reportage of dreams could be facilitated with cues. Three different types of cues were examined: semantic cues related to the themes of dreams, event cues related to experiences from the day before the dream, and color-names. On the whole, cuing increased the reportage of dreams beyond free-recall, with semantic cues related to the theme of dreams being the most effective prompts. The results were discussed in terms of findings from the study of amnesia and theories of memory that emphasize the retrieval cuing.

Dream Reports and Autobiographical Memory

Two experiments investigated autobiographical memory by studying dream reports. The continuity of autobiographical memory in the waking state and in sleep was demonstrated via Crovitz and Schiffman's retention function. The retention function was found to hold for vivid memories of dreams and vivid memories of waking experiences. It was also found to hold for waking events referenced in dream reports. In addition, the incidence of day residues was examined. About half of the dream reports collected included references to waking events of the previous day. The results were discussed in light of Freud's theory of dreams and cognitive theories of memory.

Memory Processes Involved in Morning Recall of Mental Rem-Sleep Experience: A Psycholinguistic Study

For two nights 10 subjects were asked to recall their mental sleep experience after experimental awakening during REM sleep (night report) and again upon spontaneous morning awakening (morning report). The two types of report were subjected to linguistic analysis and compared. The number of sentences used to describe the mental sleep experience, their syntactic structures, and over-all report length were similar. Those contents common to both reports were in both cases encoded in about one fourth of the sleep-related kernel sentences, these kernel sentences being distributed over about two-thirds of the sentences of the report, generally the longer ones. The organization of the morning reports reflects the consolidation of the contents in memory. The only significant physiological variable, waking time, was negatively correlated to the numbers of kernel sentences and sentences reproducing contents previously encoded in the night reports. The organization of the morning report primarily appears to be the result of retrieval and encoding procedures relative to the mental sleep experience preceding the night awakening rather than simply to the encoded contents of the night report.

Analyzing Modifications across Dream Reports

Reports of 56 dreams from 5 subjects, given upon awakening during the second REMP, were analyzed and compared with a further 3 reports of each dream, obtained the following morning, 3 days, and 1 wk. later, using a system of Coding Units (CUs) and the Scoring System for Latent Structure of Foulkes. There were no significant differences between the second, third, and fourth reports, while the most important differences between the first and subsequent reports concerned: (a) a decrease in the number of CUs, words and sentences as indicated by the scoring; (b) a partial restructuring of the material, interpretable as secondary revision; (c) a decrease in the motivational component (interactive sentences) vs the cognitive component (associative sentences); (d) a decrease in the interactive sentences with Ego present in the text vs those without Ego present. Results are discussed in the light of interference and repression hypotheses.

Memory Processes in Morning Recall after Multiple Night Awakenings

Some episodes of mental sleep experience which are reported after multiple awakenings during sleep are not recalled in the morning. Have they decayed or are they temporarily inhibited to retrieval? Responses of 10 men were recorded for four non-consecutive nights; they were awakened each night four times after 9 win. of REM sleep. Upon each awakening they were asked to report their mental sleep experience, and in the morning they were asked to re-report these experiences. Where subjects were unable to provide a spontaneous morning report they were prompted using a probe, the probe being the first contentful proposition of the corresponding night report. Subjects were aware of this design. All the night and morning reports were subjected to linguistic analysis. Spontaneous morning reports were significantly less frequent than night reports, but the use of the probe significantly increased the frequency of morning reports. Both spontaneous and probed morning reports and their corresponding night reports shared similar linguistic structures, but the probed reports and their corresponding night reports were shorter. The percentage of contents common to night and morning reports was similar for both spontaneous and probed morning reports, as was the stability of the serial position of those contents. We suggest that, with respect to settings with only one night awakening, multiple awakenings increase retrieval difficulty for entire episodes of mental sleep experience but not for single contents.

The Memory Experiences and Dreams Questionnaire (MED-Q): A Validated Measure of Dream Remembering

Dream recall has been investigated via various means, often relying upon self-report judgments. Such methods, as well as individual differences and cognitive correlates of dream recall, rarely acknowledge models, theory, or empirical work concerning waking memory. Study 1 presents the development and psychometric validation of the Memory Experiences and Dreaming Questionnaire (MED-Q)—a 30-item measure of autobiographical and dream memory sensations incorporating items on dreaming, sensory experiences, and autobiographical remembering behaviors. It produces a single score and can be broken down into its constituent factors: “awareness of dreaming,” “daydreaming,” “dream sensations upon waking,” “déjà-states,” “comprehensibility of dream content,” and “senses.” Study 2 demonstrates the validity of the MED-Q as compared with dream report indices of dream detail. The MED-Q measures the extent to which a person engages with their dream memories through both frequency and subjective characteristic ratings. It is therefore novel in emphasizing the context of autobiographical memory for dreaming.

Non-dreamers

OBJECTIVE

Assess incidence and clarify whether diagnostic correlates exist for sleep laboratory patients reporting a lack of dream recall. To awaken, during polysomnographically defined sleep including rapid eye movement (REM) sleep, individuals reporting never having experienced a dream, and determine whether they report dreaming.

METHODS

Study # 1 - Incidence and polysomnographic correlates of sleep lab patients responding on questionnaire that they had never experienced dreaming. Study # 2 - Phone interviews with those individuals reporting non-dreaming on questionnaire to reassess incidence. Study # 3 - After reassessment, individuals (non-dreamers - # 16) are awakened during polysomnographic defined sleep (including REM sleep) and queried about dream recall. This group is compared statistically to a group (rare-dreamers - # 12) that reported dreaming as an extremely rare occurrence (mean dream recall latency - 13.5 years).

RESULTS

Study # 1: Incidence of questionnaire reported non-dreaming in this sleep laboratory population is 6.5% (N=534) and is associated with the diagnosis of obstructive sleep apnea (specificity 95.6% for respiratory disturbance index >15). Study # 2 - Individuals who report after interview to have never experienced dreaming are more unusual (0.38% of this sleep laboratory population). Study # 3 - None of the non-dreamers (# 16) reported dream recall after waking in the sleep laboratory (36 awakenings in total for this group). This group does not differ, based on polysomnographic, clinical, or demographic variables, from the rare-dreaming group that occasionally reported dreams when awakened (3/12 patients, 3/32 awakenings) - a finding consistent with the reports of previous studies.

CONCLUSION

The experience of dreaming may not be as ubiquitous as generally accepted. The group of non-dreamers evaluated in this study reports never having recalled a dream and reports no dreams when awakened during polysomnographicly defined sleep. These individuals might not experience dreaming.

Completeness and accuracy of morning reports after a recall cue: comparison of dream and film reports

Our goal was to test the efficiency and accuracy of a complementary morning report, after recall cue, of an experience (having a dream or viewing a film) made and first described during the night. Twenty participants were awakened 10 min after the onset of the second REM sleep. Upon awakening, on one night they described the dream they just had and on the other night they were presented a 4-min video, then had to describe it. A new description requested in the morning after a recall cue yielded an important amount of new information both for the film and the dreams, and for the film, where the accuracy could be checked, 86% of this new information was accurate. Some aspects of the results pointed to an effect of hypermnesia. In conclusion, the morning additional information after recall cue stems from a good access to the memory of the night experience.

Daily reports of posttraumatic nightmares and anxiety dreams in Dutch war victims

A selected sample of outpatients (n = 39) suffering from "delayed" posttraumatic symptoms (more than 40 years after the original war traumatization) took part in an investigation in which posttraumatic nightmares and anxiety dreams were analyzed over a 4-week period on the basis of a daily systematic dream account. Subjects were asked to fill out a questionnaire that focused on different aspects of posttraumatic re-experiencing during dreams at home and immediately after waking up, covering a period of 28 consecutive days. All the subjects were initially screened with a standardized psychiatric interview, the Impact of Event Scale, the Symptom Check List-90, and the Clinician-Administered PTSD Scale. Nightmares were most strongly related to recalled dream content and recalled dream content was strongly associated with war experiences. The original traumatic event was often present in the form of what seemed to be an exact replay ("replication") of the original event. Replication and repetition were significantly correlated. The reliability of reports of nightmare content proved to be good.

Age differences in dreams. II: Distortion and other variables

Age-related change in manifest dream content was assessed in dreams recalled from REM sleep by fifty-eight men aged twenty-seven to sixty-four and in dreams recalled from sleep at home. There was evidence of a small-age-related decline in dream distortion (bizarreness) and family-related content, with family-related content most prominent from ages thirty-five to fifty-five. Overall the effect of increasing age on dream content is slight.