Five dollars a night got students to sleep, and their grades followedWe paid college students about $5 a night to sleep at least 7 hours – and their grades quickly improved

Researchers at the University of Pittsburgh recruited more than 1,100 undergraduates and gave them a Fitbit, the watch-like activity tracker. Of those, 468 were picked at random to get about $5 the next morning for any night they slept at least seven hours.

What the money bought

Over four weeks, the paid group hit seven hours on 26% more nights than the students who got no money. That worked out to 19 extra minutes per school night — roughly the difference between shutting the laptop at 11:40pm and shutting it at midnight.

Their GPA that semester was about 0.08 points higher. For scale: the gap between students who arrived with above-average and below-average high school grades is about 0.32 points, so this clawed back a quarter of it.

When the money arrives matters

It had to come every morning. Paying a lump sum at the end of the semester produced only about two-thirds of the effect on sleep.

Bedtime reminders and morning feedback with no money attached did almost nothing — those students slept only marginally more. After the payments stopped, the extra sleep lasted about a month; two semesters on, the GPA difference was no longer detectable.

The problem was never motivation

Before any of this, the average student in the study slept 6.6 hours a night. Half were going to bed after 1am on average, a quarter after 2am. They hit seven hours on only 43% of nights.

Two-thirds said they usually slept seven hours; the trackers showed only about a third of them managed it on even three nights out of five. And 94% said their ideal night was longer than what they were getting.

So what was missing was not the wish to sleep, but doing it night after night. The question the findings really put to universities is about their own timetables: late-night assignment deadlines and 8am classes help students sleep, or get in the way?