During my PhD, I studied the mechanisms of stereoscopic depth perception using human psychophysics and monkey physiology with Prof. Ichiro Fujita at Osaka University. After my PhD, I moved to the University of Pennsylvania as a post-doctoral researcher and examined the neural mechanisms of perceptual decisions using monkey physiology with Prof. Joshua Gold. Since 2017, I started working again on human visual psychophysics at Prof. Johannes Burge’s laboratory at the University of Pennsylvania as a research associate.
日時： 2019年12月26日(木) 16:30-18:00
場所： 京都大学 医学研究科 先端科学研究棟1F 小会議室
Suboptimal visual averaging reveals compulsory, nonlinear mechanisms in human vision
土井隆弘 博士（Dr. Takahiro Doi）
Department of Psychology, University of Pennsylvania
How humans integrate ambiguous and conflicting signals has been a focus of perception and decision-making research for decades. Identifying the source of suboptimality can reveal the information integration strategy used by the nervous system to solve ecologically relevant tasks in natural environments. In this study, we examined visual spatial averaging, a fundamental process underlying the transformation of noisy local signals into a more stable global estimate. A novel paradigm was used to measure the degree of human suboptimality against the ideal observer. In this talk, first I will establish that human visual averaging is suboptimal in both luminance and stereoscopic domains: the visual system does not faithfully compute the average of a spatially varied stimulus, especially when spatial variability is large. Then, I will present a series of experiments designed to identify the source of suboptimality. Our results indicate two kinds of nonlinear mechanisms at work: one is related to the down-weighting of outlier samples and the other is the spatial interaction among nearby signals within a stimulus. These compulsory nonlinear mechanisms, while suboptimal in our laboratory task, may reflect an information integration strategy that improves performance in more natural contexts cluttered with object boundaries and illumination variation.