Abstract
Orientation and position of small image segments are considered to be two fundamental low-level attributes in early visual processing, yet their encoding in complex natural stimuli is underexplored. By measuring the just-noticeable differences in noise perturbation, we investigated how orientation and position information of a large number of local elements (Gabors) were encoded separately or jointly. Importantly, the Gabors composed various classes of naturalistic stimuli that were equated by all low-level attributes and differed only in their higher-order configural complexity and familiarity. Although unable to consciously tell apart the type of perturbation, observers detected orientation and position noise significantly differently. Furthermore, when the Gabors were perturbed by both types of noise simultaneously, performance adhered to a reliability-based optimal probabilistic combination of individual attribute noises. Our results suggest that orientation and position are independently coded and probabilistically combined for naturalistic stimuli at the earliest stage of visual processing.
Highlights
It has been long known that luminance information arrives from the retina to the visual cortex in a topographically organized arrangement [1,2], yet the nature, precision and the underlying mechanism by which this information is coded and used during natural object and scene perception is unclear
We found that the observed values of justnoticeable difference (JND) at the same pedestal level were significantly different across the image classes (repeated-measures 2-way ANOVA, F(2,18) = 33.43 p < .001, η2 = .788)
We found that the predicted JNDs of both models were close to the observed ones
Summary
It has been long known that luminance information arrives from the retina to the visual cortex in a topographically organized arrangement [1,2], yet the nature, precision and the underlying mechanism by which this information is coded and used during natural object and scene perception is unclear. One typical approach to this problem focuses on the perceptual tolerance of the human visual system to either local element position (i.e. topographical jitter) or local element orientation noise in a range of laboratory-generated simple artificial stimuli. Previous investigations have found that for isolated lines or Gabor-patches, human sensitivity to orientation differences is around 1 ̊ [6,7]. Using isolated Gabor and Gaussian patches, Levi and co-workers [8,9] found that the visual
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