Browsing by Subject "Form perception"

Now showing 1 - 3 of 3

Open Access
Differences in illumination estimation in #thedress
(Association for Research in Vision and Ophthalmology Inc., 2017) Toscani, M.; Gegenfurtner, K. R.; Doerschner, K.
We investigated whether people who report different colors for #thedress do so because they have different assumptions about the illumination in #thedress scene. We introduced a spherical illumination probe (Koenderink, Pont, van Doorn, Kappers, & Todd, 2007) into the original photograph, placed in fore-, or background of the scene and-for each location-let observers manipulate the probe's chromaticity, intensity and the direction of the illumination. Their task was to adjust the probe such that it would appear as a white sphere in the scene. When the probe was located in the foreground, observers who reported the dress to be white (white perceivers) tended to produce bluer adjustments than observers who reported it as blue (blue perceivers). Blue perceivers tended to perceive the illumination as less chromatic. There were no differences in chromaticity settings between perceiver types for the probe placed in the background. Perceiver types also did not differ in their illumination intensity and direction estimates across probe locations. These results provide direct support for the idea that the ambiguity in the perceived color of the dress can be explained by the different assumptions that people have about the illumination chromaticity in the foreground of the scene. In a second experiment we explore the possibility that blue perceivers might overall be less sensitive to contextual cues, and measure white and blue perceivers' dress color matches and labels for manipulated versions of the original photo. Results indeed confirm that contextual cues predominantly affect white perceivers.
Open Access
Specular motion and 3D shape estimation
(Association for Research in Vision and Ophthalmology Inc., 2017) Dövencioğlu, D. N.; Ben-Shahar, O.; Barla, P.; Doerschner, K.
Dynamic visual information facilitates three-dimensional shape recognition. It is still unclear, however, whether the motion information generated by moving specularities across a surface is congruent to that available from optic flow produced by a matte-textured shape. Whereas the latter is directly linked to the firstorder properties of the shape and its motion relative to the observer, the specular flow, the image flow generated by a specular object, is less sensitive to the object's motion and is tightly related to second-order properties of the shape. We therefore hypothesize that the perceived bumpiness (a perceptual attribute related to curvature magnitude) is more stable to changes in the type of motion in specular objects compared with their matte-textured counterparts. Results from two twointerval forced-choice experiments in which observers judged the perceived bumpiness of perturbed spherelike objects support this idea and provide an additional layer of evidence for the capacity of the visual system to exploit image information for shape inference. © 2017 The Authors.
Open Access
Vision: a systems neuroscience perspective
(Uskudar University, 2014) Kafalıgönül, Hulusi
The visual system is the most studied part of the cortex, providing a basis for understanding not only visual processing per se but also the fundamental operations of the brain in general. Significant progress has been made in understanding neural structures sensitive to different visual attributes such as form, surface brightness, color and motion. Here, the basic neural structures and processing pathways for these visual features are reviewed. Dysfunctions in these processing pathways lead to deficits in the perception of different aspects of a visual object. In recent years, there is a growing interest in applying accumulated knowledge in vision science to investigate altered neural structures and abnormal perceptual processing observed in neurological disorders. Key issues and clinical studies are also discussed within the context of visual feature processing.