AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |
Back to Blog
Summary of shadows of doubt10/28/2022 ![]() ![]() Further, we investigate the functional usefulness of ensemble perception and its efficiency, and we consider possible physiological and cognitive mechanisms that underlie an individual's ability to make accurate and rapid assessments of crowds of objects. In this review, we provide an operational definition of ensemble perception and demonstrate that ensemble perception spans across multiple levels of visual analysis, incorporating both low-level visual features and high-level social information. It defines foundational limits on cognition, memory, and behavior. Ensemble perception refers to the visual system's ability to extract summary statistical information from groups of similar objects-often in a brief glance. To understand visual consciousness, we must understand how the brain represents ensembles of objects at many levels of perceptual analysis. Therefore, although we are insensitive to inconsistencies in shadows and lighting direction, the visual system seems to roughly model global lighting conditions in scenes using summary statistics. Mean discrimination thresholds for both the realistic shadows and the two-tone images were precise and surprisingly similar for both stimulus types, demonstrating that, at least for relatively simple scenes, observers can perceive the mean shadow orientation even when there is heterogeneity in the orientation of the shadows. Subjects were presented with a heterogeneous group of either shadow or two-tone images, and asked to compare the mean shadow/lighting orientation to a test image. ![]() We created a second set of stimuli by converting those same 50 images into two-tone pictures that were not perceived as shadows, but rather as opaque paint. ![]() The resulting images contained a shaded object with a cast shadow (consistent with each of the 50 possible lighting directions). Could shadow information across a scene be represented by summary statistics? To test this, we rendered a set physically realistic images of a simple three-dimensional object illuminated by a single light source from one of 50 different orientations. For example, observers perceive the average size of a group of randomly sized objects (Ariely, Psych Sci, 2001 Chong & Treisman, Vis Res, 2003), and the average identity of a group of faces (Haberman & Whitney, Curr Bio, 2007). Several recent studies have shown that the visual system represents scenes with summary statistics. Our inability to accurately detect contradictory shadows in a scene suggests that shadow information is computed at an early, local scale, and that global factors such as lighting direction are not explicitly represented by the visual system. Shadows provide information about object motion and depth, but they must also be discounted to accurately recover surface properties and lightness. ![]()
0 Comments
Read More
Leave a Reply. |