Behavioral/Cognitive Highly Informative Natural Scene Regions Increase Microsaccade Production during Visual Scanning

Classical image statistics, such as contrast, entropy, and the correlation between central andnearby pixel intensities, are thought to guide ocular fixation targeting.However, these statistics are not necessarily task relevant and therefore donot provide a complete picture of the relationship between informativeness and ocular targeting. Moreover, it is not knownwhether 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. Herewe developed an objectivemeasure 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 inmore 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. Increasedmicrosaccade production was not explained by increased fixation dura-tion, suggesting that the visual system specifically uses microsaccades to heighten information acquisition from informative regions. Key words: fixation duration; natural images; saccades; scanpath; scene statistics; visual searc