Why do we have dreams? Dreaming is a complicated experience that can take on numerous emotional tones and simulate reality to varying degrees.
It is a consequence of our brain’s neurophysiology. As a result, there is no definitive solution to this question.
A study led by the universities of Geneva (UNIGE) and Toronto, as well as the Geneva University Hospitals (HUG), compared the dreams of two forager communities in Tanzania and the Democratic Republic of the Congo to those of individuals living in Europe and North America. It showed that the first two groups produced more threatening, but also more cathartic and socially oriented dreams than the Western groups.
The results show how strong the links are between the socio-cultural environment and the function of dreams.
The hallucinatory experience of dreaming is universal among all humans. It transpires with greater frequency throughout the paradoxical Rapid Eye Movement (REM) phase of sleep. However, it is possible for dreaming to happen during any stage of slumber.
What are the physiological, emotional or cultural functions of dreams? Does it regulate our emotions? Does it prepare us to deal with a specific situation?
Recent theories suggest that during a “functional” dream, the individual simulates more threatening and/or social situations, which would have an evolutionary advantage in promoting adapted behavior to real-life situations.
To put these theories to the test, researchers from UNIGE and the University of Toronto compared the content of the dreams of the BaYaka in the Democratic Republic of the Congo and the Hadza in Tanzania — two communities whose way of life is similar to that of our hunter-gatherer ancestors — with that of different groups of people living in Europe and North America (Switzerland, Belgium, Canada), including healthy participants and patients with psychiatric disorders.
Adaptive Dynamic Scenarios
For the BaYaka and Hadza, dream narratives were collected over a two-month period in the field by anthropologists from the University of Toronto. Data on Western groups’ dreams came from previous studies published between 2014 and 2022.
“We discovered that the dreams of the BaYaka and Hadza are very dynamic. They often begin with a situation of danger, in which life is threatened, but end up staging a means of coping with this threat, unlike the scenarios in the Western groups we observed,”
explained Lampros Perogamvros, a privat-docent and group leader in the Departments of Psychiatry and Basic Neurosciences at the UNIGE Faculty of Medicine, and an attending physician at the HUG Center for Sleep Medicine, who led the study.
Conversely, clinical populations — such as individuals afflicted with social anxiety or nightmares — experience vivid dreams devoid of a cathartic emotional resolution. It appears that the adaptive function of dreaming is lacking in these latter groups.
The researchers discovered that among the responses available to Indigenous people when confronted with a threat in their dreams, those related to social support were extremely common.
This is the case, for example, when an Indigenous person reports a dream in which he is hit by a buffalo in the middle of the bush, only to be rescued by a member of his community.
Alternatively, in a dream, another individual falls into a well and is assisted by one of his companions. Each of these dreams has its own unique emotional resolution.
“Among the BaYaka and Hadza, the social bonds they have are, by necessity, very strong. Compared to the more individualist societies in Europe and North America, day to day life and division of labor is typically more egalitarian. It appears this kind of social connection, and reliance on community means that the best way they process the emotional content associated with threat in their dreams, is by way of the social relationships they have. In effect these relationships are the emotional tools used to process life’s challenges,”
explained David Samson, Associate Professor of Evolutionary Anthropology at the University of Toronto, Mississauga, and first author of the study.
The research team consequently proposes that there exists a close relationship between the purpose of dreams and the values and norms of each particular society under study.
“However, it is difficult to deduce any causal links between the dreams and daytime functioning in this study. Nor should we conclude that dreams in groups of Western individuals have no emotional function,”
Indeed, a study conducted by the aforementioned research team in 2019 demonstrated that “bad dreams,” which refer to negative-themed dreams that do not qualify as nightmares, frequently function as preparatory exercises for our actual anxieties when we awaken.
“There seems to be more than one type of ‘functional’ dreams. The present study shows that there is a strong link between our socio-cultural life and the function of dreams,”
concluded the researcher.
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.
- Samson, D.R., Clerget, A., Abbas, N. et al. Evidence for an emotional adaptive function of dreams: a cross-cultural study. Sci Rep 13, 16530 (2023). doi: 10.1038/s41598-023-43319-z