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Samson DR, Clerget A, Abbas N, Senese J, Sarma MS, Lew-Levy S, Mabulla IA, Mabulla AZP, Miegakanda V, Borghese F, Henckaerts P, Schwartz S, Sterpenich V, Gettler LT, Boyette A, Crittenden AN, Perogamvros L. Evidence for an emotional adaptive function of dreams: a cross-cultural study. Sci Rep 2023; 13:16530. [PMID: 37783728 PMCID: PMC10545663 DOI: 10.1038/s41598-023-43319-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Accepted: 09/22/2023] [Indexed: 10/04/2023] Open
Abstract
The function of dreams is a longstanding scientific research question. Simulation theories of dream function, which are based on the premise that dreams represent evolutionary past selective pressures and fitness improvement through modified states of consciousness, have yet to be tested in cross-cultural populations that include small-scale forager societies. Here, we analyze dream content with cross-cultural comparisons between the BaYaka (Rep. of Congo) and Hadza (Tanzania) foraging groups and Global North populations, to test the hypothesis that dreams in forager groups serve a more effective emotion regulation function due to their strong social norms and high interpersonal support. Using a linear mixed effects model we analyzed 896 dreams from 234 individuals across these populations, recorded using dream diaries. Dream texts were processed into four psychosocial constructs using the Linguistic Inquiry and Word Count (LIWC-22) dictionary. The BaYaka displayed greater community-oriented dream content. Both the BaYaka and Hadza exhibited heightened threat dream content, while, at the same time, the Hadza demonstrated low negative emotions in their dreams. The Global North Nightmare Disorder group had increased negative emotion content, and the Canadian student sample during the COVID-19 pandemic displayed the highest anxiety dream content. In conclusion, this study supports the notion that dreams in non-clinical populations can effectively regulate emotions by linking potential threats with non-fearful contexts, reducing anxiety and negative emotions through emotional release or catharsis. Overall, this work contributes to our understanding of the evolutionary significance of this altered state of consciousness.
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Affiliation(s)
- David R Samson
- Sleep and Human Evolution Lab, University of Toronto, Mississauga, Canada.
- Department of Anthropology, University of Toronto, 3359 Mississauga Road, Mississauga, ON, L5L 1C6, Canada.
| | - Alice Clerget
- Department of Basic Neurosciences, University of Geneva, Geneva, Switzerland
| | - Noor Abbas
- Sleep and Human Evolution Lab, University of Toronto, Mississauga, Canada
| | - Jeffrey Senese
- Sleep and Human Evolution Lab, University of Toronto, Mississauga, Canada
| | - Mallika S Sarma
- School of Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Sheina Lew-Levy
- Department of Human Behavior, Ecology and Culture, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - Ibrahim A Mabulla
- Department of Archaeology and Heritage, Institute of Resource Assessment, University of Dar es Salaam, Dar es Salaam, Tanzania
| | - Audax Z P Mabulla
- Department of Archaeology and Heritage, Institute of Resource Assessment, University of Dar es Salaam, Dar es Salaam, Tanzania
| | - Valchy Miegakanda
- Laboratoire National de Santé Publique, Brazzaville, Republic of the Congo
| | - Francesca Borghese
- Department of Basic Neurosciences, University of Geneva, Geneva, Switzerland
| | - Pauline Henckaerts
- Department of Basic Neurosciences, University of Geneva, Geneva, Switzerland
| | - Sophie Schwartz
- Department of Basic Neurosciences, University of Geneva, Geneva, Switzerland
| | - Virginie Sterpenich
- Department of Basic Neurosciences, University of Geneva, Geneva, Switzerland
| | - Lee T Gettler
- Department of Anthropology, University of Notre Dame, Notre Dame, IN, USA
| | - Adam Boyette
- Department of Human Behavior, Ecology and Culture, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | | | - Lampros Perogamvros
- Department of Basic Neurosciences, University of Geneva, Geneva, Switzerland.
- Department of Psychiatry, Center for Sleep Medicine, University Hospitals of Geneva, Geneva, Switzerland.
- Department of Psychiatry, Center for Sleep Medicine, 2 Chemin du Petit-Bel-Air, 1226 Thônex, Switzerland.
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Abbas NH, Samson DR. Dreaming during the COVID-19 pandemic: Support for the threat simulation function of dreams. Front Psychol 2023; 14:1124772. [PMID: 36814654 PMCID: PMC9939895 DOI: 10.3389/fpsyg.2023.1124772] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Accepted: 01/17/2023] [Indexed: 02/08/2023] Open
Abstract
Evolutionary theories suggest that dreams function as a world simulator of events that maximizes our ability to surmount social and threat-related challenges critical to survivorship and reproduction. Here, in contrast to the incorporation continuity hypothesis, we test the (1) social bias hypothesis, which states that dreams will overrepresent positive social interactions relative to waking life, (2) the mutually exclusive threat bias hypothesis, the idea that dream content will be negative relative to waking life, (3) the strengthening hypothesis, which states that dreams will rehearse more positive interactions with individuals the self is familiar with relative to waking life, and (4) the compensation hypothesis, which states that social contents in dreams increases during periods of social seclusion. Dream (n = 168) and wake (n = 184) reports were collected through a standardized online survey from 24 undergraduate students. Recalls were analyzed using the Social Content Scale. Generalized linear mixed effects models were used, and the following fixed-effects were considered for the study; the number of reports contributed, report state, biological sex, stress, social support, and media exposures. Results showed support for the threat bias hypothesis, we found that dreams were more negative and featured more unfamiliar individuals in contrast to waking life. Additionally, we found partial support for the social bias and the strengthening hypotheses, however no support was shown for the compensation hypothesis. Overall, these results demonstrate support for the threat simulation function of dreams.
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Predicting the affective tone of everyday dreams: A prospective study of state and trait variables. Sci Rep 2019; 9:14780. [PMID: 31611647 PMCID: PMC6791936 DOI: 10.1038/s41598-019-50859-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Accepted: 09/15/2019] [Indexed: 01/01/2023] Open
Abstract
Although emotions are reported in a large majority of dreams, little is known about the factors that account for night-to-night and person-to-person variations in people’s experience of dream affect. We investigated the relationship between waking trait and state variables and dream affect by testing multilevel models intended to predict the affective valence of people’s everyday dreams. Participants from the general population completed measures of personality and trauma history followed by a three-week daily journal in which they noted dream recall, valence of dreamed emotions and level of perceived stress for the day as well as prior to sleep onset. Within-subject effects accounted for most of the explained variance in the reported valence of dream affect. Trait anxiety was the only variable that significantly predicted dream emotional valence at the between-subjects level. In addition to highlighting the need for more fine-grained measures in this area of research, our results point to methodological limitations and biases associated with retrospective estimates of general dream affect and bring into focus state variables that may best explain observed within-subject variance in emotions experienced in everyday dreams.
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Tuominen J, Stenberg T, Revonsuo A, Valli K. Social contents in dreams: An empirical test of the Social Simulation Theory. Conscious Cogn 2019; 69:133-145. [PMID: 30769273 DOI: 10.1016/j.concog.2019.01.017] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Revised: 01/29/2019] [Accepted: 01/29/2019] [Indexed: 11/25/2022]
Abstract
Social Simulation Theory (SST) considers the function of dreaming to be the simulation of social events. The Sociality Bias and the Strengthening hypotheses of SST were tested. Social Content Scale (SCS) was developed to quantify social events. Additionally, we attempted to replicate a previous finding (McNamara et al., 2005, Psychological Science) of REM dreams as predisposed to aggressive, and NREM dreams to prosocial interactions. Further, we investigated the frequency and quality of interactions in late vs early REM and NREM dreams. Data consisted of wake, REM and NREM home dream reports (N = 232, 116, 116, respectively) from 15 students. Dreams overrepresented social events compared to wake reports, supporting the Sociality Bias hypothesis. However, the Strengthening Hypothesis was not supported. We weren't able to replicate the McNamara et al. finding, and no time of night effect was found. While SST gained partial support, further research on social contents in dreams is required.
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Affiliation(s)
- Jarno Tuominen
- Department of Psychology, University of Turku, FI-20014 Turku, Finland; Turku Brain and Mind Center, University of Turku, FI-20014 Turku, Finland.
| | - Tuula Stenberg
- Department of Psychology, University of Turku, FI-20014 Turku, Finland
| | - Antti Revonsuo
- Department of Psychology, University of Turku, FI-20014 Turku, Finland; Turku Brain and Mind Center, University of Turku, FI-20014 Turku, Finland; Department of Cognitive Neuroscience and Philosophy, School of Biosciences, University of Skövde SE-54128, Skövde, Sweden
| | - Katja Valli
- Department of Psychology, University of Turku, FI-20014 Turku, Finland; Turku Brain and Mind Center, University of Turku, FI-20014 Turku, Finland; Department of Cognitive Neuroscience and Philosophy, School of Biosciences, University of Skövde SE-54128, Skövde, Sweden
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