The orientation dependence of the Hermann grid illusion.
The Hermann grid illusion (HGI), elicited by a grid displayed as either horizontal-vertical (HV) or oblique (45 degrees ) configuration, was measured as the luminance necessary to cancel the illusory spots at the grid intersections. Overall, the HGI produced by the oblique grid was about one-third of that produced by the HV grid. The observers exhibited different sensitivities to the HGI orientation, and seemed to perceive the illusion in two manners: with moderate anisotropy (reduction of about 20%, three subjects) or large anisotropy (90% reduction, four subjects). The quantitative reduction of the HGI elicited by the oblique pattern tested and its reduction to almost zero in some subjects, constitute a benchmark for any model aimed at explaining the HGI on psychophysical grounds.
De Lafuente
Victor
V
Departamento de Fisiologia, Biofisica y Neurociencias, Centro de Investigacion y de Estudios Avanzados del IPN, Av. IPN 2508 07360, Mexico DF, Mexico.
Ruiz
Octavio
O
D000293:Adolescent; D000328:Adult; D016880:Anisotropy; D015350:Contrast Sensitivity / Q000502:physiology; D003463:Cues; D005260:Female; D006801:Humans; D007088:Illusions / Q000502:physiology*; D008029:Lighting; D008297:Male; D008959:Models, Neurological; D015588:Observer Variation; D009949:Orientation / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation; D013028:Space Perception / Q000502:physiology*; D014794:Visual Fields / Q000502:physiology*