Detection of symmetry and anti-symmetry : what they might reveal about visual nonlinearities

• Main Author: Mancini, Sandra
• Format: Others
• Published: 2004
• Online Access: http://spectrum.library.concordia.ca/8050/1/MQ94632.pdf; Mancini, Sandra <http://spectrum.library.concordia.ca/view/creators/Mancini=3ASandra=3A=3A.html> (2004) Detection of symmetry and anti-symmetry : what they might reveal about visual nonlinearities. Masters thesis, Concordia University.

The detection of symmetry and anti-symmetry was investigated by manipulating check size, spatial frequency, grey scale range and eccentricity. Sensitivity to symmetrical stimuli was only modestly affected by these manipulations. The most interesting findings were from anti-symmetrical stimuli. For the anti-symmetrical binary scale stimuli low thresholds were found but these increased to undetectable levels as check size decreased. The high-pass filtering of binary displays only modestly affected performance for anti-symmetrical stimuli; however, the low-pass filtering of these stimuli greatly impaired performance. Increasing the grey scale range of the stimuli led to the undetectability of anti-symmetry. When stimuli with black and white checks were moved from fixation to 8{493} in the periphery, performance was greatly impaired for anti-symmetrical stimuli. A single model employing a full or half wave rectification would not be able to account for such divergent results.