Abstract
Performance in most visual discrimination tasks is better along the horizontal than the vertical meridian (Horizontal-Vertical Anisotropy, HVA), and along the lower than the upper vertical meridian (Vertical Meridian Asymmetry, VMA), with intermediate performance at intercardinal locations. As these inhomogeneities are prevalent throughout visual tasks, it is important to understand the perceptual consequences of dissociating spatial reference frames. In all studies of performance fields so far, allocentric environmental references and egocentric observer reference frames were aligned. Here we quantified the effects of manipulating head-centric and retinotopic coordinates on the shape of visual performance fields. When observers viewed briefly presented radial arrays of Gabors and discriminated the tilt of a target relative to homogeneously oriented distractors, performance fields shifted with head tilt (Experiment 1), and fixation (Experiment 2). These results show that performance fields shift in-line with egocentric referents, corresponding to the retinal location of the stimulus.
Highlights
Discriminability and the speed of information processing differ as a function of eccentricity and isoeccentric locations across the visual field [1,2,3,4,5]
The results of Experiment 1 support the proposal that performance fields shift with head tilt and are specified in terms of egocentric coordinates
The Vertical Meridian Asymmetry (VMA) was weak in comparison to this Horizontal-Vertical Anisotropy (HVA); yet, performance in the S location tended to be superior to performance in the N location in the Head Upright condition, and in the SE versus NW locations in the Head Tilted condition
Summary
Discriminability and the speed of information processing differ as a function of eccentricity and isoeccentric locations across the visual field [1,2,3,4,5]. Performance fields show a characteristic shape for different stimulus orientations and luminance levels, with both monocular and binocular viewing conditions [5] These asymmetries become more pronounced as eccentricity, spatial frequency, and the number of distracters are increased [2,5,11,15]. Before describing our specific experiments, we first review the relevant dissociations between egocentric and allocentric reference frames, and how such manipulations affect related visual phenomena
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