Psychophysical evidence for competition between real and illusory contour processing

Luminance defined and illusory contours provide vital information about object borders. However, real and illusory contour cues tend to be used under different contexts and can interfere with one another. Although some cells in visual cortex process both real and illusory contours equivalently, recent studies (Ramsden et al 2001) suggest competitive interactions between real (feedforward) and illusory (feedback) contour processing in primate V1 and V2. To test this hypothesis psychophysically, we designed stimuli in which illusory contours are presented with and without the presence of real line components. If real and illusory contour cues are processed by the same mechanism, then the presence of both cues should enhance the percept. If the illusory percept is degraded by the presence of real lines, then independent real and illusory mechanisms are suggested. The perception of a Kanisza-triangle, presented for 250 msec, was measured under three conditions: 1) virtual contour alone, 2) with a short parallel real line superimposed on the virtual contour or 3) with a short orthogonal real line abutting the virtual contour. The real lines were varied from sub- to supra-threshold contrasts. In a 2AFC paradigm three subjects fixated on a spot in the triangle center and indicated whether the side of the triangle was bent outwards or inwards. We found that real lines degraded the percept of the illusory contour (i.e. increased angular thresholds). Such interference occurred even at subthreshold real line contrasts and, in some subjects, was greater for the parallel than orthogonal real line. Our results support the presence of separate mechanisms for the processing of real and illusory contours and suggest that, under some circumstances, real cues can interfere with the processing of illusory cues. We suggest that such interferences occurs by the feedforward influences of the lines which interfere with the feedback influences prominent during illusory contour processing

University of Dayton Professor Umesh Haritashya honored with SOCHE Faculty Excellence Award for research into climate change, geological impacts

University of Dayton geologist Umesh Haritashya was recognized in August with a 2020-21 SOCHE Faculty Excellence Award for his contributions to understanding the relationship between climate change and natural disasters in alpine environments

Six UD students claim McGrath Award for research in Catholic intellectual traditions

Six University of Dayton students recently received 2022 Fr. Jack McGrath, S.M., Awards for Research in Catholic Intellectual Traditions and presented their research at the annual Catholic Intellectual Tradition symposium

Six UD students receive 2023 McGrath Award for research in Catholic intellectual traditions

Six UD students received Fr. Jack McGrath, S.M., Awards for Research in Catholic Intellectual Traditions at the annual Catholic Intellectual Tradition symposium

University of Dayton Chorale Selected for Virtual Performance at 2022 Ohio Music Education Association Professional Development Concert

The University of Dayton Chorale will perform virtually at the 2022 Ohio Music Education Association’s Professional Development Conference, the third largest musical conference in the nation

Computer engineering student creates public speaking simulator with faculty mentor

Inspired by his own struggles with public speaking, UD junior Bao Truong created a VR simulator to allow users to practice presentations before a computer-generated crowd

Students share disability research in collaboration with Brighter Connections Theatre

University of Dayton students learned about the experiences of people with disabilities through a research project with Brighter Connections Theatre

Doctoral student receives Cross Award for commitment to equity, community engagement

UD doctoral student Ashley Wright was honored for her commitment to academic innovation in the areas of equity, community engagement and teaching

UD students honored with Horwitz/Horowitz Award for undergraduate research in physiology

Two UD students received 2022 Barbara A. Horwitz and John M. Horowitz Undergraduate Research Awards from the American Physiological Society