title: Conjunction and linear non-separability effects in visual shape encoding.
abstract: Four visual search experiments are reported which used simple 2D shapes varying on the global dimensions of aspect ratio/curvature or aspect ratio/tapering. Results indicate serial self-terminating search in all conditions. Most importantly, search rates are markedly modulated by the particular forms of structural relations existing between the targets and their distractors. Thus, single-feature targets with shape properties that are linearly separable from those of their distractors yield markedly faster search rates than linearly separable targets made of a conjunction of distractor features. In addition, linearly separable single-feature targets are searched at a much faster rate than single-feature targets which are not linearly separable. Follow-up experiments demonstrate that these conjunction and linear non-separability effects cannot be attributed to pairwise target-distractor discriminability differences across conditions. The main conclusions are that the shapes used are parsed according to elementary features in visual encoding, and that a linear discrimination mechanism is available which permits fast visual search rates if a single-feature target is linearly separable from its distractors.
authors.affiliation: Groupe de Recherche en Neuropsychologie Expérimentale, Département de Psychologie, Université de Montreal, CP 6128, Succ. Centre-ville, Quebec, H3C 3J7, Montréal, Canada. arguinm@psy.umontreal.ca
authors.forename: M
authors.initials: M
authors.lastname: Arguin
authors.forename: D
authors.initials: D
authors.lastname: Saumier
mesh_terms: D000328:Adult; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D010470:Perceptual Masking / Q000502:physiology