Researchers from the University of Bern have found a significant connection between the quality of our deep sleep and how likely we are to engage in prosocial behaviors, such as cooperating with others and making charitable donations. The study shows that brain activity during deep sleep, particularly in the right temporoparietal junction, can predict prosocial tendencies in everyday life. The results have been published in The Journal of Neuroscience.
Human societies thrive on cooperation and altruism, with individuals regularly participating in actions that benefit others, such as volunteering or donating to charities. Despite the importance of such behaviors, there is considerable variation in how prosocial individuals are. Prior research has linked prosocial behavior to several psychological and biological factors, but the role of sleep has only recently come under scrutiny.
Sleep, especially its deeper stages, is crucial for various cognitive functions and overall well-being. Prior research has established a link between sleep and various cognitive and emotional functions, including how we interact socially. Studies have shown that lack of sleep can reduce altruism, trust, and overall social engagement.
However, these studies often focused on the impact of sleep deprivation rather than examining how natural sleep patterns could influence behavior. The specific neural mechanisms through which sleep influences prosocial behavior have also remained largely unexplored. This study was driven by a hypothesis that the quality of deep sleep, as reflected in brain waves known as slow waves, could be a key player in this process.
“We have evidence from previous studies conducted during wakefulness that neural activation during rest can account for individual differences in prosocial preferences. Given the relative stability of slow-wave activity during sleep, we were interested as to whether similar correlations could be identified,” said study author Daria Knoch, a professor of social neuroscience at the University of Bern.
Slow-wave activity during sleep refers to the deep, restorative stage of sleep characterized by slow brain waves, known as delta waves. These waves are prominent on an EEG (electroencephalogram) and represent the deepest phase of non-rapid eye movement (NREM) sleep. Slow-wave activity plays a key role in physical recovery, memory consolidation, and overall brain health. It occurs in longer periods during the first half of the night and is associated with the brain’s processing and restoration from daily activities.
The study included 54 healthy, right-handed individuals who reported sleeping between seven to eight hours per night. The participants were carefully screened to meet specific inclusion criteria, such as normal sleep patterns, no history of neurological or psychiatric disorders, and no significant drug or alcohol use.
Each participant’s sleep was recorded in their home environment to ensure natural sleep conditions. They were equipped with a high-density portable EEG system, which included 64 electrodes placed on the scalp to measure electrical brain activity. This setup allowed the researchers to capture detailed data on sleep architecture, particularly focusing on slow-wave activity in the brain.
“The sleep data were collected using a portable polysomnographic system with 66 EEG electrodes on the scalp of the participants’ heads, allowing them to experience natural sleep at home,” explained co-first author Mirjam Studler about the procedure.
Concurrently, prosocial behavior was assessed using the Public-Good Game, a standard tool in economic experiments to measure cooperative behavior. In this game, each of three participants was given an amount of money (in the form of points) and could choose to keep it or contribute some or all of it to a common pot.
Contributions to the pot were matched and then divided equally among all participants, thus creating a scenario where individual contributions benefited the group at a potential personal cost. The researchers doubled each contribution to the pot to incentivize participation, making the game’s stakes realistic and consequential.
The researchers found that individuals who exhibited higher levels of slow-wave activity in the right temporoparietal junction during deep sleep tended to be more generous in the Public-Good Game. This behavior indicates a higher level of cooperative and altruistic tendencies.
The temporoparietal junction is known for its role in social cognition, including empathy and perspective-taking — the ability to understand and consider others’ viewpoints. The findings suggest that the quality of sleep could enhance the functionality of this brain area, thereby influencing social and empathetic behaviors.
“Our findings suggest that sufficient sleep depth in the temporoparietal junction, a brain area involved in perspective taking, may serve as a dispositional indicator of social cognition ability, shedding light on the link between sleep and prosocial behavior,” Knoch told PsyPost.
She was surprised by “the specificity of our results, since we analyzed the whole brain. Moreover, we recruited good sleepers (i.e. 7-8 h per night) and still we found variation in slow-wave activity that could explain variation in behavior.”
While the study presents compelling evidence linking deep sleep to prosocial behavior, there are limitations. The sample size, though adequate for initial exploration, is relatively small for generalizing the findings across a broader population. Additionally, the observational nature of the study means that causation cannot be conclusively established—whether deeper sleep leads to more prosocial behavior or if inherently prosocial individuals have different sleep patterns remains to be determined.
Future research could expand by including a more diverse participant pool and employing experimental manipulations of sleep to directly test causality. As technology advances, interventions to enhance the quality of deep sleep in specific brain regions could be developed, potentially opening new avenues for fostering prosocial behavior.
“We are only at the beginning of research that explores a new approach, namely the combination of sleep parameters and economic preferences,” Knoch said. “First evidence should not be overinterpreted, but rather further research should be conducted first.”
The study, “Human Prosocial Preferences Are Related to Slow-Wave Activity in Sleep,” was authored by Mirjam Studler, Lorena R. R. Gianotti, Janek Lobmaier, Angelina Maric, and Daria Knoch.