title: Horizontal-vertical filters in early vision predict anomalous line-orientation identification frequencies.
abstract: A characteristic of early visual processing is a reduction in the effective number of filter mechanisms acting in parallel over the visual field. In the detection of a line target differing in orientation from a background of lines, performance with brief displays appears to be determined by just two classes of orientation-sensitive filter, with preferred orientations close to the vertical and horizontal. An orientation signal represented as a linear combination of responses from such filters is shown to provide a quantitative prediction of the probability density function for identifying the perceived orientation of a target line. This prediction was confirmed in an orientation-matching experiment, which showed that the precision of orientation estimates was worst near the vertical and horizontal and best at about 30 degrees each side of the vertical, a result that contrasts with the classical oblique effect in vision, when scrutiny of the image is allowed. A comparison of predicted and observed frequency distributions showed that the hypothesized orientation signal was formed as an opponent combination and horizontal and vertical filter responses.
authors.affiliation: Department of Communication and Neuroscience, University of Keele, Staffordshire, U.K.
authors.forename: D H
authors.initials: DH
authors.lastname: Foster
authors.forename: P A
authors.initials: PA
authors.lastname: Ward
mesh_terms: D005374:Filtration; D006801:Humans; D008954:Models, Biological; D011336:Probability; D014796:Visual Perception / Q000502:physiology*