Pointer J S, 1996, "Evidence of a global oblique effect in human extrafoveal vision" Perception 25(5) 523 – 530
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Evidence of a global oblique effect in human extrafoveal vision
Jonathan S Pointer
Received 20 November 1995, in revised form 26 January 1996
Abstract. Analysis of recently published human contrast-sensitivity data obtained along thecardinal and major oblique visual-field meridians of a single subject has demonstrated a consistently greater sensitivity at a given eccentricity to horizontally oriented as compared with obliquely oriented gratings. This difference was evident not only at foveal but also at several eccentric loci over arange of low to medium spatial frequencies. This observation is to be distinguished in extrafoveal fixation from the well-documented oblique effect, which describes the variation in sensitivity with orientation at a single visual-field locus. With periodic stimuli which were well localised in space and frequency, and had comparable spatial-summation properties, a spatial-frequency dependency of what could be termed the global oblique effect could be demonstrated along isoeccentric contours centred on the fovea (eccentricity 0 deg) out to an eccentricity of at least 40 deg.