Could paying students to sleep improve their marks?

What if one of the simplest ways to improve students' grades wasn't more homework, tutoring or extra study, but instead paying them to go to bed? 

Research published in the Journal of Political Economy tested exactly that in an experiment involving more than 1,100 university students. 

The researchers offered some students US$4.75 if they managed to get at least seven hours of sleep on a weeknight and it worked! 

Rather than simply asking students when they went to bed, each participant was given a Fitbit. The devices measured movement and heart rate, allowing the researchers to estimate when students fell asleep, when they woke up and how long they slept. 

Students were monitored before the intervention to establish their normal sleeping patterns, followed by four weeks of experimentation and then another one to five weeks of observation afterwards. 

At the beginning of the study, students managed at least seven hours of sleep on only around 43 percent of weeknights. 

Then the researchers divided them into different groups, a control group who wore their Fitbits and completed the surveys but otherwise carried on as normal and an experiment group who were challenged to sleep for at least seven hours by 9am on a weeknight. 

If their Fitbit showed they had achieved it, they earned US$4.75. 

Each student in the main treatment group was given a personalised bedtime target based on their normal sleeping pattern, generally around an hour earlier than their usual bedtime.  Thirty minutes before that target, they received a reminder. 

The researchers then created several other experimental groups to tease apart which parts of the intervention were changing behaviour. 

One group could earn the same financial reward, but instead of receiving the money immediately, their accumulated payments arrived at the end of the study. 

Another could earn the delayed financial reward but didn't receive the nightly reminders or daily feedback. 

A further group received the bedtime reminders and morning feedback, including happy or unhappy emojis depending on whether they had reached their sleep target, but received no money at all. 

During the four-week experiment, students receiving the immediate incentives became substantially more likely to get at least seven hours of sleep. 

Their average weeknight sleep increased by about 19 minutes which was enough to push many students across the seven-hour threshold. 

The timing of the reward mattered with immediate incentives producing a larger improvement in sleep during the intervention than delayed payments or reminders and feedback without money. 

Getting the money tomorrow morning appeared to be more motivating than knowing the same money would arrive weeks later. 

Then the researchers stopped paying the students and found during the following one to five weeks, students were still sleeping around eight minutes longer per weeknight than they had before the experiment. 

The researchers also obtained the students’ academic records from the university and found the students receiving the immediate sleep incentives improved their average semester course performance by around 0.075–0.089 grade points, equivalent to roughly 0.10–0.11 standard deviations. 

So the students slept more, and their academic performance improved too. 

Then the question became, if the students are spending more hours asleep, what are they doing less of? 

Screen time! Students reported spending less time browsing the internet, watching television and videos or playing games, particularly around bedtime. 

The study raises an interesting question about how we try to change behaviour. 

Perhaps knowing what is good for us isn't always enough, what matters is when we experience the reward.

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