Researchers at Uppsala University Sweden investigated the relationship between sleep deprivation and facial recognition behaviors. Their results indicate that those who experience sleep deprivation reduce the overall time they observe faces and tend to perceive them as less attractive and trustworthy. These findings suggest that the chronically sleep-deprived could experience challenges in social interactions and perceive others in a more negative light.
The study, published in Nature of Science and Sleep journal, examined how long their sleep-deprived subjects observed faces and the accuracy with which they identified the expressed emotion. Based on prior research Lieve van Egmond and colleagues guessed sleep deprivation would slow the perception process and subjects would stare longer at faces. They also hypothesized that angry, fearful, or happy faces would see the smallest increase in observation time. In addition, past research indicated that sleep-deprived individuals are more likely to identify robust emotions rather than neutral ones.
The research team found 45 subjects from the general population. Each reported they were good sleepers, drank moderate amounts of caffeine and alcohol, habitually went to bed between 10 pm-12 am, and were not suffering from jet lag. These 45 participants served as their own control and were assessed after one night of complete sleep deprivation and one night with 8 hours of sleep. These two nights were one week apart.
After both the sleepless night and one with the recommended amount of sleep, the participants were shown the same 24 faces. The order of the faces was randomized in both trials. Eye tracking software was used to determine how long each subject fixated on the face. They were also asked to rate the face on trustworthiness, attractiveness, and health measures.
Contrary to what was expected, sleep-deprived subjects spent between 6.3% and 10% less time examining the faces they were presented with compared to the day they were well-rested. They also rated the fearful and angry faces as less attractive, less healthy, and less trustworthy when sleep-deprived. Happy faces were rated no different in either condition.
Van Egmond and his team also showed participants the top half of the faces separate from the bottom half. In this condition, sleep-deprived participants demonstrated reduced observation of the top half of the face. Prior research findings indicated that the eyes are crucial to identifying emotions in others.
According to the research team, the study’s findings may be limited by a few factors. First, the faces used were only of Caucasian models. Diverse models may have yielded different results. Second, participants were between 23-28 years old; this demographic may have different patterns in facial observation than those older. Finally, the range of emotions studied was limited to happy, fearful, angry, and neutral.
This research contributes to what is already known about the consequences of sleep deprivation. Van Egmond and colleagues state, …”spending less time fixating on faces after acute sleep loss may come along with several problems for social interactions, e.g., inaccurate and delayed judgment of the emotional state of others.”
The study, “How Sleep-Deprived People See and Evaluate Others’ Faces: An Experimental Study”, was authored by Lieve van Egmond, Elisa Meth, Shervin Bukhari, Joachim Engström, Maria Ilemosoglou, Jasmin Annica Keller, Shiyang Zhou, Helgi B. Schiöth, and Christian Benedict.