Scale-invariance in brightness illusions implicates object-level visual processing.
Brightness illusions demonstrate that an object's perceived brightness depends on its visual context, leading to theoretical explanations ranging from simple lateral inhibition to those based on the influence of knowledge of and experience with the world. We measure the relative brightness of mid-luminance test disks embedded in gray-scale images, and show that rankings of test disk brightness are independent of viewing distance, implying that the rankings depend on the physical object size, not the size of disks subtended on the retina. A single filter that removes low spatial frequency content, adjusted to the diameters of the test disks, can account for the relative brightness of the disks. We note that the removal of low spatial frequency content is a principle common to many different approaches to brightness/lightness phenomena; furthermore, object-size representations--as opposed to retinal-size representations--inherently remove low spatial frequency content, therefore, any process that creates object representations should also produce brightness illusions.
Department of Psychology American University, Washington, DC, USA.
Erica
E
Dixon
Department of Psychology American University, Washington, DC, USA.
Arthur
A
Shapiro
Ohio State University, Columbus, OH, USA.
Zhong-Lin
ZL
Lu
D006801:Humans; D007088:Illusions / Q000502:physiology*; D008027:Light; D010775:Photic Stimulation / Q000379:methods; D012160:Retina / Q000502:physiology*; D014785:Vision, Ocular / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*