Abstract
After adapting to monocularly presented color stimulus, an observer may experience an aftereffect with the same hue as the adaptor (positive aftereffect) if the contour of the adaptor was presented to the unadapted eye (Sato & Nakajima, 2010, ECVP). We investigated the mechanisms underlying this positive aftereffect. The adaptor was a colored square (2ox2o). The adaptor hue was either red (L-M), green (M-L), blue (+S) or yellow (-S). In each trial an adaptor was presented to one eye for 1s, followed by a test phase, in which the observer was to match the hue and contrast of a test patch with the aftereffect. There were three test conditions: (1) the monocular condition: a square frame surrounding the adapted area was presented to the adapted eye; (2) the dichoptic condition: the test frame was presented to the unadapted eye; and (3) the no-frame condition. Compared with the no frame condition, the presence of a frame increased the aftereffect by 22-110% across different colors. The aftereffect in the dichoptic condition had the same hue as the adaptor but opposite hue in the monocular condition. Replacing the square with a cross in the test phase, the positive aftereffect occurred only near the bars and shaped like a diamond, suggesting such effect is induced by the edges. Showing either adaptor or test frame binocularly dramatically reduced the aftereffect. The observer perceived a negative aftereffect in the dichoptic condition when a luminance mask was presented to the unadapted eye and an enhanced positive aftereffect if the mask was presented to the adapted eye, suggesting that positive and negative aftereffects coexist in different eyes. Since the context was added only in the test phase, the positive aftereffects cannot be explained by simultaneous contrast. Instead, an interocular suppressive lateral interaction was needed to explain our result.
Meeting abstract presented at VSS 2014