Chronotype and Time of Day Effects on Face Processing: Early ERP Correlates

Face recognition is a pervasive and important ability in daily life. Although familiar face recognition is seemingly easy and efficient, recognition of unfamiliar faces is difficult and highly error prone, and can be affected by various situational and individual variables. Our objective was to explore whether chronobiological variables can influence face recognition. The present study sought to understand if chronotype (individual preference for the morning or evening period) and the time-of-day when the task was performed (in synchrony or asynchrony with the preferred time) influence performance and early ERP correlates of face processing.Thirty-two participants (16 evening-types, 16 morning-types, assessed with the Morningness-Eveningness Questionnaire) performed the tasks twice, at their peak and off-peak times (7:30am and 7:30pm), with a one-week interval between sessions, while their EEG was recorded. One task was a modified version of the Glasgow Face Matching Task (GFMT), consisting on the presentation of 80 sequential pairs of faces, and participants were required to indicate whether the second face of each pair was the same or different from the first face. The other task was a Famous Face Recognition Task, where participants saw 96 randomly presented facial photographs (half famous, half non-famous, with ovals covering hair and external face features) and were asked to indicate whether each photo was of a famous or a non-famous individual. Time-of-first session and the order of the tasks were counterbalanced between participants. All stimuli were different between sessions. Although no significant chronotype or time-of-day effects were observed on behavioural performance in either task, results showed a significant time-of-day x chronotype interaction on the P100 component amplitude for both tasks. Morning-types registered higher amplitudes in the evening session, compared to the morning session, regardless of type of stimuli. Response accuracy was strongly and positively correlated with P100 amplitudes for both morning and evening sessions. No interaction between time-of-day and chronotype was found for the N170 component in either task. These results suggest an early visual attentional asynchrony effect only for morning-types. On the other hand, no (a)synchrony effects were evident on more face-specific processing stages.