Scan patterns during the processing of facial expression versus identity: An exploration of task-driven and stimulus-driven effects Department of Psychology, University of Edinburgh, Edinburgh, Scotland,& Departments of Neurology, Ophthalmology and Visual Sciences, University of British Columbia, Canada George L. Malcolm Departments of Neurology, Ophthalmology and Visual Sciences, University of British Columbia, Canada Linda J. Lanyon Department of Psychology, University of Edinburgh, Edinburgh, Scotland Andrew J. B. Fugard Departments of Neurology, Ophthalmology and Visual Sciences, University of British Columbia, Canada,& Department of Psychology, University of British Columbia, Canada Jason J. S. Barton Perceptual studies suggest that processing facial identity emphasizes upper-face information, whereas processing expressions of anger or happiness emphasizes the lower-face. The two goals of the present study were to determine (a) if the distributions of eye fixations reflect these upper/lower-face biases, and (b) whether this bias is task- or stimulus-driven. We presented a target face followed by a probe pair of morphed faces, neither of which was identical to the target. Subjects judged which of the pair was more similar to the target face while eye movements were recorded. In Experiment 1 the probe pair always differed from each other in both identity and expression on each trial. In one block subjects judged which probe face was more similar to the target face in identity, and in a second block subjects judged which probe face was more similar to the target face in expression. In Experiment 2 the two probe faces differed in either expression or identity, but not both. Subjects were not informed which dimension differed, but simply asked to judge which probe face was more similar to the target face. We found that subjects scanned the upper-face more than the lower-face during the identity task but the lower-face more than the upper-face during the expression task in Experiment 1 (task-driven effects), with significantly less variation in bias in Experiment 2 (stimulus-driven effects). We conclude that fixations correlate with regional variations of diagnostic information in different processing tasks, but that these reflect top-down task-driven guidance of information acquisition more than stimulus-driven effects. Keywords: face expression, face identity, scanpath, fixation Citation: Malcolm, G. L., Lanyon, L. J., Fugard, A. J. B., & Barton, J. J. S. (2008). Scan patterns during the processing of facial expression versus identity: An exploration of task-driven and stimulus-driven effects. Journal of Vision, 8(8):2, 1–9, http://journalofvision.org/8/8/2/, doi:10.1167/8.8.2. Introduction When subjects inspect a visual scene, they often do so with not just a single fixation, but a series of fixations distributed among different regions of the scene. These shifts in fixation serve to re-direct both the fovea, the area of retina with the highest resolving capacity for spatial detail, and the locus of attention, which is often (but not always) correlated with the locus of fixation. Thus, shifts of fixations bring new perceptual data to the observer, while at the same time the perceptual data processed by the observer determines where subsequent fixations should be directed. This renders “seeing” an active process, with interplay between vision and eye move- ments (Henderson, 2003). Although early studies of scanning behavior showed significant inter-subject variability in the way different observers scan the same stimulus (Noton & Stark, 1971), fixations are not distributed randomly. Rather, the inter- play between eye movements and perception that lies behind the distribution of fixations likely reflects a process of acquiring information for a perceptual judgment (Deco & Schu ¨rmann, 2000; Rybak, Gusakova, Golovan, Journal of Vision (2008) 8(8):2, 1–9 http://journalofvision.org/8/8/2/ 1 doi: 10.1167/8.8.2 Received July 22, 2007; published June 2, 2008 ISSN 1534-7362 * ARVO Downloaded from jov.arvojournals.org on 05/16/2019