Sleep Deprivation Impairs the Recognition of Emotions

A new study investigated the impact of sleep deprivation on the ability to recognize the emotional intensity of human facial expressions. The results were published this month in the journal Sleep.

The study involved 37 healthy adults between 18 and 25 years of age. Seventeen participants were assigned to the control group. They slept normally at home for a night. The other 20 participants were kept awake in a sleep lab for about 31 hours.

Then everyone performed an emotional face recognition task at about 4 p.m. Both groups returned home for a night of sleep. Then they repeated the task the next day.

The task involved the presentation of black and white photos of the same man. The images were taken from Dr. Paul Ekman’s Pictures of Facial Affect set. In the photos the man made happy, sad, angry and neutral expressions.

Each of the three emotional pictures was morphed to the neutral face using computer software. This produced a set of 10 images for each emotion representing an equal gradient of change.

For each emotion the 10 images were presented in random order on a laptop computer screen. Participants had to rate the strength of emotion for each face.

Results show that the ability to recognize angry and happy facial expressions was blunted in the sleep-deprived group. They were able to detect extreme emotions. But they struggled to detect expressions of moderate intensity. There was no change in the recognition of sad expressions.

These differences were most reliable and significant in women. The impairment was corrected by one night of recovery sleep.

The authors suggested that facial expressions may be the most significant visual cue in human communication. Abnormal face processing can lead to impaired social interactions.

They also wrote that accurate emotional face judgments are of critical importance for many professionals. Examples include emergency responders, medical staff and soldiers. This ability also is vital for new parents.

The results also suggest that healthy young women may be more sensitive to some effects of sleep loss. This may help explain why women are more likely than men to develop major depression.

Last year the Sleep Education Blog reported that being awake for 12 hours or more may impair the ability to recognize a familiar face. Read more about sleep deprivation.

Image by nebojsa mladjenovic

Sleep & Memory: “That Face Looks Familiar”

Studies show that there is a strong link between sleep and memory. A new study even examines how sleep affects memory for face identity. Does sleep help you recognize a familiar face?

The study involved 112 volunteers; their average age was 25 years. Each participant was shown 60 computer-generated faces in random order.

The heads were bald, and the faces had no unique features such as a mole or a scar. Each face was shown on a computer screen for two seconds at a time. The entire set of faces was shown five times.

Recognition was tested after varying periods of time. Some people were tested after getting sleep; others were tested before getting any sleep. Sixty faces were shown; 30 faces had been seen earlier, and 30 were new faces that had never been seen before.

The results do not show that sleep enhances memory strength. But they do suggest that time spent awake during the retention period impairs memory for face identity.

Wakefulness of 12 hours or more had a detrimental impact on recognition memory strength; it made participants less likely to feel familiar with a test face.

The authors suggest that ongoing sensory stimulation when awake may interfere with visual memory. Sleep may not actively enhance visual memory; but it may temporarily prevent memory loss by “sheltering” visual memory from interference.

Read the full text of the study online.