Abstract
To evaluate the relative importance of local feature and spatial filter models for hyperacuity, vernier thresholds were determined for gratings consisting of a fundamental ( F o) and third harmonic (3 F) presented alone, and added together in compound gratings where the relative phase offsets of 3 F to F o was 0, 90, 180 and 270°. Thresholds were determined for a range of spatial frequencies of F o (0.5–16 c deg −1) for abutting and non-abutting stimuli. Compound grating vernier performance was found to be: (i) invariant with relative phase offset for the abutting and non-abutting conditions; and (ii) predictable from the vernier thresholds for the individual grating components making up the compound stimulus. The results support a view that supra-threshold components in a multi-frequency stimulus act independently and it is the spatial frequency content, not the local feature characteristics, which limit vernier performance.
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