Abstract
Perception of brightness depends on transients created by eye movements: a stabilized image fades in seconds following its onset. We examined how brightness perception depends on temporal change of retinal signals using blob stimuli; when viewed under steady fixation, these approximate stabilized images by minimizing the effects of abrupt retinal signals from involuntary eye movements. Our stimuli were two spatial sinusoidal blobs presented simultaneously on a gray background. One of them was the test stimulus, whose intensity changed like a temporal analog of the Craik-Cornsweet stimulus, with periodic abrupt changes and slower sinusoidal change between them. The other, the matching stimulus, had a time course defined by abrupt transitions only. We determined the reference contrasts that matched the brightness of the test blob at the extremes of its sinusoidal modulation. In the results, the matching reference contrasts indicated some discounting of the continuous modulation of the test stimulus: a weak temporal Craik-Cornsweet illusion. This is consistent with the view that the slow fading of stable images represents a persisting central effect of retinal transients rather than a central time-differentiation of maintained retinal signals.