Individuals with insomnia misrecognize angry faces as fearful faces while missing the eyes: an eye-tracking study

Individuals with insomnia have been found to have disturbed perception of facial expressions. Through eye movement examinations, here we test the hypothesis that this effect is due to impaired visual attention functions for retrieving diagnostic features in facial expression judgments. Twenty-three individuals with insomnia symptoms and 23 controls without insomnia completed a task to categorize happy, sad, fearful, and angry facial expressions. The participants with insomnia were less accurate in recognizing angry faces and misidentified them as fearful faces more often than the controls. A hidden Markov modeling approach for eye movement data analysis revealed that when viewing facial expressions, more individuals with insomnia adopted a nose-mouth eye movement pattern focusing on the vertical face midline while more controls adopted an eyes-mouth pattern preferentially attending to lateral features, particularly the two eyes. As previous studies found that the primary diagnostic feature for recognizing angry faces is the eyes while the diagnostic features for other facial expressions involve the mouth region, missing the eye region may contribute to specific difficulties in recognizing angry facial expressions, consistent with our behavioral finding in participants with insomnia symptoms. Taken together, the findings suggest that impaired information selection through visual attention control may be related to the compromised emotion perception in individuals with insomnia.