Helping each other is among the more consequential things our species does, and what determines whether someone chooses to help is not well pinned down. Sleep is an unglamorous candidate. Three replicating studies tested it at three scales at once. They were one night of sleep loss in the laboratory with imaging, several nights tracked in daily life, and a whole country losing an hour to .
Helping fell at every scale. One night of sleep loss triggered withdrawal of help from one individual to another, and fMRI showed that withdrawal associated with deactivation of key nodes in the . Night-to-night reductions in sleep predicted corresponding next-day reductions in choosing to help. And one hour of lost from the Daylight Saving transition reduced real charitable donations.
Humans help each other, and that habit has been one of the forces shaping modern civilizations. What determines whether a person chooses to help on any given occasion is much less settled, and sleep had not been on the list of candidate factors.
Three replicating studies tested it at three different scales: within individuals, across individuals, and across societies. The point of the design is that the three have different weaknesses, so agreement between them is harder to explain away than any single result.
At the individual level, one night of sleep loss triggered the withdrawal of help from one individual to another. The fMRI findings tied that withdrawal to deactivation of key nodes within the social cognition brain network that supports prosociality. At the group level, night-to-night reductions in sleep across several nights predicted corresponding next-day reductions in the choice to help others during ordinary interactions.
At the national level, one hour of lost sleep opportunity inflicted by the transition to Daylight Saving Time reduced real-world altruistic helping through donation giving, established by analyzing over 3 million charitable donations. The authors conclude that inadequate sleep is a significant force determining whether humans help one another. Weigh the scales differently, though: only the first study manipulated sleep, and the clock change alters more than sleep alone.
wat. One lost hour of sleep opportunity across a country showed up as less money given to charity, in over three million donations.
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Three methods with different weaknesses pointing the same way is worth more than any one of them. A laboratory effect, a diary effect and a national natural experiment do not share the same confounds.
How do we know?
Ben Simon and colleagues combined a laboratory sleep-loss experiment with fMRI, an ecological study of night-to-night sleep against next-day helping, and analysis of over 3 million charitable donations around the Daylight Saving Time transition.
What is still unknown
The national result is an observational natural experiment, so the Daylight Saving transition brings other changes besides lost sleep. Only the individual-level study manipulated sleep, and it is the smallest of the three.
Learn something?
Where to next
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