Asymmetries in oriented-line detection indicate two orthogonal filters in early vision

D. H. Foster, P. A. Ward

    Research output: Contribution to journalArticlepeer-review


    Visual detection of a line target differing in orientation from a background of lines may be achieved speedily and effortlessly. Such performance is assumed to occur early in vision and to involve filter mechanisms acting in parallel over the visual field. This study establishes orientational limits on this performance and analytically derives some generic properties of the underlying filters. It was found that, in brief displays, target orientation detection thresholds increased approximately linearly with background orientation, from minima at 0° (vertical) and 90°, whereas background orientation detection thresholds decreased approximately linearly with target orientation, from maxima at 0° and 90°. Target and background threshold functions were exactly antisymmetric. These data are shown to indicate a model of early line processing dominated by two classes of orientation-sensitive filter with axes close to the vertical and horizontal and orientation-tuning half-widths each of approximately 30° at half-height.
    Original languageEnglish
    Pages (from-to)75-81
    Number of pages6
    JournalProceedings of the Royal Society B: Biological Sciences
    Issue number1306
    Publication statusPublished - 1991


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