Sleep-related attentional bias for faces depicting tiredness in insomnia: evidence from an eye-tracking study

Study Objectives: To date, evidence of an attentional bias in insomnia has mostly been obtained through reaction time tasks, with a limited number of studies using eye tracking. Here, using an eye-tracking paradigm, this study sought to determine whether individuals with insomnia display an attentional bias for novel faces depicting tiredness. Methods: Individuals with insomnia (n = 20) and normal sleepers (n = 20) viewed a series of face pairs depicting neutral and tired expressions each for periods of 4000 milliseconds. Eye movements were recorded using eye tracking, and first fixation onset, first fixation duration, total fixation duration, and total gaze duration were examined for three interest regions (eyes, nose, mouth). Results: Significant group × face interactions for total fixation duration and total gaze duration indicated that, regardless of interest-region, participants with insomnia spent more time fixating on and observing tired faces relative to neutral faces when compared with normal sleepers. Additionally, significant group × face × interest-region interactions for total fixation duration and total gaze duration indicated that participants with insomnia spent more time observing the eye region of the tired faces than the eye region of the neutral faces when compared with normal sleepers. Conclusions: Individuals with insomnia display an attentional bias toward tired faces, more specifically for the eye region compared to normal sleepers. These findings contribute to our understanding of face perception in insomnia and provide more objective support for cognitive models of insomnia, suggesting that individuals with insomnia selectively attend to faces for tiredness cues.