Abstract
Although substantial work has been done on diurnal fluctuations of visual attention and memory, much less is known about time-of-day influences on processing visual social stimuli, or how such influences interact with chronotype (preference for being active earlier or later in the day). Here, we examined how perception of facial expression intensity varies with chronotype, match between chronotype and time of testing, and time of testing per se (morning or evening). College students (51 female, 18 male) rated emotional intensity of black-and-white facial images of two individuals from the NimStim face set. Software was used to blend neutral expressions with sadness, happiness, anger, or surprise to create ten intensity steps for each emotion. Stimuli were presented on a monitor under standard fluorescent lighting with external light blocked from the room. Subjects were defined as either evening or non-evening chronotype based on scores on the Horne-Ostberg Morningness-Eveningness Questionnaire (MEQ) and sleep midpoint from self-reports of the previous night of sleep, and allowed to select a morning (7-10 AM) or evening (7-10 PM) session. Chronotype and match between chronotype and testing time did not significantly affect expressiveness ratings. However, exploratory analyses yielded a significant main effect of test-time for sad and angry faces (but not happiness or surprise) in the upper range of expressiveness. Evening testing produced higher ratings. Control analyses indicated that this relationship was not due to evening types and non-evening types selecting evening/ morning sessions, respectively. Thus, young adults appear to perceive strongly negative facial expressions as especially negative when viewed in the evening. The absence of a pure chronotype effect may reflect the small number of extreme morning types in our sample. The results underscore the potential importance of taking time of day into account in studies of visual facial emotion processing.
Meeting abstract presented at VSS 2018