A luminance-induced expansion aftereffect.

We report a novel luminance-induced expansion aftereffect in which adaptation to sawtooth luminance modulation with a slow decreasing phase causes subsequently viewed uniform luminance or static patterns to appear to expand. Eight observers were adapted to luminance ramps and judged the appearance of subsequent static and contracting test patterns. The magnitude of this expansion aftereffect was quantified using a nulling paradigm; on average, the illusory expansion was canceled when the test pattern contracted at ∼ 0.3°/s. This expansion aftereffect is qualitatively distinct from the brightening aftereffect previously associated with this sawtooth luminance adaptation, suggesting dissociable perceptual consequences of luminance-change adaptation for brightness and spatial coding.