Ben Simon E, Vallat R, Rossi A, Walker MP (2022)
PLoS Biol 20(8): e3001733.
https://doi.org/10.1371/journal.pbio.3001733
Abstract
Humans help each other. This fundamental feature of homo sapiens has been one of the most powerful forces sculpting the advent of modern civilizations. But what determines whether humans choose to help one another? Across 3 replicating studies, here, we demonstrate that sleep loss represents one previously unrecognized factor dictating whether humans choose to help each other, observed at 3 different scales (within individuals, across individuals, and across societies). First, at an individual level, 1 night of sleep loss triggers the withdrawal of help from one individual to another. Moreover, fMRI findings revealed that the withdrawal of human helping is associated with deactivation of key nodes within the social cognition brain network that facilitates prosociality. Second, at a group level, ecological night-to-night reductions in sleep across several nights predict corresponding next-day reductions in the choice to help others during day-to-day interactions. Third, at a large-scale national level, we demonstrate that 1 h of lost sleep opportunity, inflicted by the transition to Daylight Saving Time, reduces real-world altruistic helping through the act of donation giving, established through the analysis of over 3 million charitable donations. Therefore, inadequate sleep represents a significant influential force determining whether humans choose to help one another, observable across micro- and macroscopic levels of civilized interaction. The implications of this effect may be non-trivial when considering the essentiality of human helping in the maintenance of cooperative, civil society, combined with the reported decline in sufficient sleep in many first-world nations.
From the Discussion section
Taken together, findings across all 3 studies establish insufficient sleep (both quantity and quality) as a degrading force influencing whether or not humans wish to help each other, and do indeed, choose to help each other (through real-world altruistic acts), observable at 3 different societal scales: within individuals, across individuals, and at a nationwide level.
Study 1 established not only the causal impact of sleep loss on the basic desire to help another human being, but further characterised the central underlying brain mechanism associated with this altered phenotype of diminished helping. Specifically, sleep loss significantly and selectively reduced activity throughout key nodes of the social cognition brain network (see Fig 1B) normally associated with prosociality, including perspective taking of others’ mental state, their emotions, and their personal needs. Therefore, impairment of this neural system caused by a lack of sleep represents one novel pathway explaining the associated withdrawal of helping desire and the decisional act to offer such help.
