Sleep. For something we spend so much time doing — by some estimates we spend one-third of our life sleeping — there is a remarkable amount we are yet to understand about it.
While there is a growing body of research examining the factors behind getting a good night’s sleep and how it may affect our bodies, there is one aspect of sleeping that continues to mystify researchers around the world: dreaming.
From Sigmund Freud’s psychoanalytic theory of dreaming, in which he described these phenomena as windows into our unconscious, to physiological theories that dreams are a by-product of spontaneous neural activity, we have long sought to understand why we dream. A new study by a team of international researchers, including from the University of Toronto, sheds some light on this question and suggests that emotions and evolution may play a role.
Are dreams a simulation?
The primary dream theory investigated by the study is the simulation theory of dream function. As the authors explain, this theory proposes that dreaming — which occurs most often during rapid-eye movement (REM) sleep — serves a biological purpose, namely to simulate evolutionary pressures and prepare us for these occurrences in our day-to-day lives.
Specifically, the researchers suggest that our dreams are particularly focused on simulations of threatening situations and social situations, and help us rehearse our behavioural responses to them in real life.
For threatening dreams, a functional response would show us potential resolutions, leading to emotional catharsis. As the study summarizes, dreams may serve an evolutionary purpose by “simulating distress in a safe environment to help process threats in beneficial ways.” If this were to be true, the authors suggest that among clinical populations, such as those with nightmare or anxiety disorders, dream would not this serve this functional purpose as there would be no emotional resolution or catharsis.
One of the study’s main critiques of prior dream research is that it has largely been focused on populations in North America and Europe (the Global North). To address this, the study included participants from the BaYaka and Hadza foraging communities in the Republic of Congo and Tanzania, respectively. Both communities share similar environmental stimuli and communal social dynamics, according to the authors.
With this in mind, they hypothesized that the dream content of the BaYaka and Hadza communities would have more community-oriented features than those in the Global North. Additionally, due to their higher mortality rates and exposure to environmental threats, it was hypothesized that the forager groups’ dreams would also feature more threat-related content.
Since the simulation theory suggests a functional emotional purpose, the researchers also hypothesized that BaYaka and Hadza dreams will serve to regulation emotions and associate threats with non-threatening contexts, and would thus feature less anxiety or negative emotions. Finally, it was hypothesized that the nightmare disorder group would demonstrate higher levels of negative emotions, and both the social anxiety group and a group of students at the University of Toronto during the COVID-19 pandemic would demonstrate higher levels of anxiety in their dreams.
Methods and Results
In total, 234 participants from two forager populations (BaYaka, Hadza) and three Global North populations (non-clinical reference group, social anxiety disorder group, and nightmare disorder group) recorded nearly 900 dreams for the researchers to analyze. This was done using the Linguistic Inquiry and Word Count software (LIWC-22), which analyzed the written descriptions of the dreams and assigned them to one of four categories: Community-oriented, Threat, Negative emotions, and Anxiety.
Overall, the researchers found that BaYaka dreams demonstrated significantly higher community-oriented content compared to all the other groups, including the Hadza, partially supporting the first hypothesis. Both forager groups’ dreams demonstrated significantly higher threat-oriented content, supporting the second hypothesis. In regards to negative emotions, the Nightmare disorder group demonstrated the highest levels while the Hadza demonstrated significantly lower levels.
The authors conclude by stating, “our results suggest indirectly that dreams can effectively regulate emotions by linking potential dangers with novel, non-fearful dream contexts and can lead to a reduction in feelings of anxiety and other negative emotions, as a form of emotional release or catharsis.”