Angeline Yang¹, Susana Chung¹; ¹UC Berkeley

It has been consistently found that people perform worse in face recognition tasks when a face is inverted, compared to when it is upright. This Face Inversion Effect (FIE) suggests that unlike objects, which are processed in parts, faces are processed holistically–a process that is disrupted with inversion. Here we aim to 1) clarify the strength of FIE on different emotions (angry, fearful, happy, sad) and 2) to assess the eye movement patterns that characterize holistic versus feature-based processing of upright and inverted expressions respectively, and investigate the effect of the inversion method (rotation/flip). As expected, subjects performed worse in identification of inverted expressions. FIE especially inhibited recognition of sad and angry faces, while recognition of happiness remained unaffected. In the analysis of eye movement, we use a machine-learning based approach (Eye Movement Hidden Markov Model) that accounts for individual differences in attentional style by learning and clustering individual HMMs containing regions of interest and transition probabilities for each subject. Consistent with literature on individual difference in face processing, two types of eye movement patterns characterizing the processing of upright expressions were identified: an analytic “eyes-focused” pattern, and a more holistic “nose/mouth-focused” pattern. Based on preliminary subject-level analysis, analytic eyes-focused subjects tended to become more holistic in the inverted condition. Similarly, most holistic nose/mouth-focused subjects tended towards more analytic eye movement in the inverted condition. Additionally, rotated faces were processed more holistically than flipped faces. These findings suggest that impaired performance in the inversion condition may be associated with deviation from an individual’s preferred eye movement pattern rather than a holistic versus feature-based difference in processing. It also highlights the importance of individual difference in eye movement and attentional strategy.