A team of psychologists and sleep researchers from Cardiff University in the United Kingdom conducted a study that reveals wearing a sleep mask can enhance cognitive function the day after use. The findings, published in the Sleep journal, add to a growing body of evidence about how light exposure at night influences brain performance during waking hours.
The research enrolled 89 volunteers who participated in a two-week protocol. In the first week, participants wore eye masks for five nights and then completed a two-day testing phase. In the following week, the same participants repeated the protocol but without the mask to serve as a control comparison.
Results showed that individuals who slept with the mask demonstrated superior performance on a word-pair learning task, indicating improved memory encoding and retrieval after sleep. They also achieved better scores on a psychomotor vigilance test, a measure of behavioral alertness and sustained attention. Taken together, these outcomes suggest that the eye mask may confer a cognitive advantage the next day by supporting certain sleep-dependent processes.
Interestingly, when participants kept sleep diaries, there was no noticeable difference in total sleep time or subjective sleep quality between the mask nights and the non-mask nights. This finding implies that the cognitive gains observed were not simply the result of longer or perceived better sleep, but potentially due to changes in sleep architecture linked to light deprivation during sleep.
A second experiment expanded the sample to 33 volunteers. In this phase, participants wore an eye mask for two nights and then wore a comparable mask that was altered with cuts for another two nights. While these two conditions differed visually, the researchers also collected electroencephalography data to monitor brain activity during sleep.
Analyses indicated that higher learning efficiency after wearing the mask correlated with an extended period of non-REM sleep. Non-REM sleep is known to be enhanced when the eyes are prevented from processing light, a condition achieved by the eye mask. The team highlighted that this extended non-REM sleep period appears linked to improved cognitive performance upon waking, reinforcing the connection between sleep quality and daytime learning capabilities.