Alignment of separated patches: multiple location tags

Gaussian and Gabor patches can be accurately localized; however, it is not yet clear which cues (or location tags) the visual system utilizes for localization. To determine the cues used in spatial alignment, we measured and modelled the perceived shifts for asymmetric Gaussian and Gabor patches over a wide range of separations, patch sizes and orientations. For Gaussian patches we observed perceived shifts that were generally consistent with that of the centroid of the envelope. For Gabor patches we found that the perceived shift depends on the carrier orientation (whether co-axial or orthoaxial with the patch arrangement), separation (in units of carrier wavelength) and patch size (number of cycles per standard deviation). Gabor patches with the carrier orthoaxial (horizontal) to the three vertically arranged patches, were similar to Gaussian patches. However, Gabor patches with the carrier coaxial (vertical) to the three vertically arranged patches resulted in perceived shifts that were consistent with a number of alternate localization primitives. The selection of primitives was dependent on mainly the separation and patch size. Our results support the suggestion that the visual system can use multiple tags for location (Hess et al., Vis Res 1994;34:2439-2451; Badcock et al., Vis Res 1996;36:1467-1472).