The phantom illusion.
It is well known that visible luminance gradients may generate contrast effects. In this work we present a new paradoxical illusion in which the luminance range of gradual transitions has been reduced to make them invisible. By adopting the phenomenological method proposed by Kanizsa, we have found that unnoticeable luminance gradients still generate contrast effects. But, most interestingly, we have found that when their width is narrowed, rather than generating contrast effects on the surrounded surfaces, they generate an assimilation effect. Both high- and low-level interpretations of this "phantom" illusion are critically evaluated.
Department of Neurological, Biomedical and Movement Sciences, University of Verona, Italy. Electronic address: alessandra.galmonte@univr.it.
Alessandra
A
Galmonte
Faculty of Development and Society, Sheffield Hallam University, United Kingdom.
Alessandro
A
Soranzo
Howard Hughes Medical Institute, Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA, USA.
Michael E
ME
Rudd
Department of Life Sciences, University of Trieste, Italy.
Tiziano
T
Agostini
D015350:Contrast Sensitivity / Q000502:physiology*; D006801:Humans; D009903:Optical Illusions / Q000502:physiology*; D019047:Phantoms, Imaging; D014796:Visual Perception / Q000502:physiology*
Contrast and assimilation effects; Lightness perception; Luminance gradients; Visual illusions