Object-based effects of attentional selection due to low-level curvature-based perceptual singularities

Recently, textures composed of smoothly varying dominant orientations were shown to generate
striking non-smooth percepts. Having no acute feature contrasts, the perceptual singularities in
these orientation-defined textures (ODTs) are accurately predicted by a model based on two
texture curvatures. Such curvature-based perceptual singularities preattentively segregate textures
into perceptually coherent regions which could interact with attentional selection processes as
high-level discrete objects have been observed to do. In the current research, textures consisting
of either piecewise constant or smoothly-varying orientations were used in a divided attention
discrimination task. Participants were asked to determine whether two probes displayed over the
textures were identical or not. For both types of textures, participants' discrimination accuracy
was found to be significantly higher when the probes were located in the same perceptual area
compared to when they were separated by a perceptual singularity. Our results indicate that
perceptual singularities in both discontinuous and smoothly varying ODTs interfere with attentional selection processes and hence can be seen as separating the visual field into primitive
low-level objects.
[Supported in part by a Psychobiology Young Investigator grant 207-07-08.]