title: Highly informative natural scene regions increase microsaccade production during visual scanning.
abstract: Classical image statistics, such as contrast, entropy, and the correlation between central and nearby pixel intensities, are thought to guide ocular fixation targeting. However, these statistics are not necessarily task relevant and therefore do not provide a complete picture of the relationship between informativeness and ocular targeting. Moreover, it is not known whether either informativeness or classical image statistics affect microsaccade production; thus, the role of microsaccades in information acquisition is also unknown. The objective quantification of the informativeness of a scene region is a major challenge, because it can vary with both image features and the task of the viewer. Thus, previous definitions of informativeness suffered from subjectivity and inconsistency across studies. Here we developed an objective measure of informativeness based on fixation consistency across human observers, which accounts for both bottom-up and top-down influences in ocular targeting. We then analyzed fixations in more versus less informative image regions in relation to classical statistics. Observers generated more microsaccades on more informative than less informative image regions, and such regions also exhibited low redundancy in their classical statistics. Increased microsaccade production was not explained by increased fixation duration, suggesting that the visual system specifically uses microsaccades to heighten information acquisition from informative regions.
authors.affiliation: Departments of Neurobiology and Neurosurgery, Barrow Neurological Institute, Phoenix, Arizona 85013, School of Mathematical and Statistical Sciences, Arizona State University, Tempe, Arizona 85287, Department of Signal Theory and Communications, University of Vigo, E-36310 Vigo, Spain, and Mind, Brain, and Behavior Research Center, University of Granada, E-18071 Granada, Spain.
authors.forename: Michael B
authors.initials: MB
authors.lastname: McCamy
authors.forename: Jorge
authors.initials: J
authors.lastname: Otero-Millan
authors.forename: Leandro Luigi
authors.initials: LL
authors.lastname: Di Stasi
authors.forename: Stephen L
authors.initials: SL
authors.lastname: Macknik
authors.forename: Susana
authors.initials: S
authors.lastname: Martinez-Conde
mesh_terms: D000465:Algorithms; D001767:Blinking; D019277:Entropy; D005145:Face; D005260:Female; D005403:Fixation, Ocular / Q000502:physiology; D006801:Humans; D008297:Male; D010775:Photic Stimulation; D012438:Saccades / Q000502:physiology*; D014785:Vision, Ocular / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
keywords: fixation duration; natural images; saccades; scanpath; scene statistics; visual search