Greco’s team found that memory formation and alertness scores did indeed improve when participants wore their masks to bed.
To explore the topic further, they designed a second experiment in which a smaller group of 35 adults wore a sleep mask to bed for five nights and then a sleep mask with eye holes cut out for two nights. This was meant to serve as a control mask that gave participants the feeling of sleeping with a mask, without the light-blocking benefits. They also wore EEG headbands to measure sleep stages during this follow-up study.
Again, those with the real mask performed better on post-study cognition tests. After analyzing the EEG data, researchers proposed this could be due to an increase in slow-wave activity in the brain while wearing sleep masks that block light from reaching the retinas.
“Given the current climate of life-hacking, sleep monitoring, and cognitive enhancers, our findings suggest the eye mask as a simple, economical, and noninvasive way to get more out of a night of sleep,” the study authors conclude.