title: T-junctions in inhomogeneous surrounds.
abstract: In an inhomogeneous checkerboard surround, the lighter check darkens an incremental test patch more than the darker check lightens it. However, decremental test patches are influenced equally [Schirillo & Shevell, 1996. Vision Research, 36, 1783-1796]. In the current study, we manipulate the spatial arrangement of a checkerboard surround to produce T-junctions that perceptually group the checks with the test patch. These stimuli alter the inducing effects of the checks. For one modified surround, increments appeared approximately 8% darker and decrements appeared approximately 10% lighter over the original checkerboard surround prior to modification. In a second modified surround, that resembled White's illusion [White, 1979. Perception, 8, 413-416], increments again appeared approximately 8% darker, while decrements appeared a dramatic approximately 23% lighter over the original checkerboard surround prior to modification. These enhanced induction effects are postulated to result from the addition of specific T-junctions. However, these grouping effects remain subservient to the asymmetrical induction effects found by Schirillo and Shevell (1996).
authors.affiliation: Department of Psychology, Wake Forest University, 27109, Winston Salem, NC, USA.
authors.forename: T O
authors.initials: TO
authors.lastname: Melfi
authors.forename: J A
authors.initials: JA
authors.lastname: Schirillo
mesh_terms: D000221:Adaptation, Ocular / Q000502:physiology; D000328:Adult; D015350:Contrast Sensitivity / Q000502:physiology*; D004867:Equipment Design; D005260:Female; D006801:Humans; D008029:Lighting; D009903:Optical Illusions