Abstract
Kaneko & Murakami (2012) showed that simultaneous contrast for brightness and for color (saturation-shift type) are both enhanced by briefly presenting the stimulus. Simultaneous contrast is a universal phenomenon seen across many visual features. So how universal is the inverse relationship between the strength of simultaneous contrast and the stimulus duration? In the first study, we examined the relationship between the simultaneous tilt contrast (a.k.a. tilt illusion) and stimulus duration. A vertical test grating (2 cpd sinusoidal) and a tilted surrounding grating (inducer) appeared repeatedly and subjects adjusted the orientation of the comparison grating to make it parallel to the test. Test and inducer appeared simultaneously and their duration was either 10 ms or 500 ms. When the inducer was tilted 15 deg away from the test, the tilt contrast effect was more than doubled for 10 ms condition compared with 500 ms condition. When the inducer was tilted 3 deg, neither duration gave any effect. For tilts greater than 9 deg, the 10 ms condition always yielded greater effect than the 500 ms condition. However, tilts of less than 9 deg gave no significant difference between durations. In the second study, we looked for similar effects of duration in hue-shift type simultaneous color contrast (cf. Klauke & Wachtler, 2015). We chose all our colors from the equiluminant cone-contrast space whose origin was the equal-energy white (20 cd/m2). Results from experiments using unique yellow as a target hue suggest that the unique-yellow shift was strongly enhanced by briefly flashing the stimulus. Results suggest the existence of universal mechanisms that enhance the difference across visual features between neighboring regions, which work only for briefly presented targets.
Meeting abstract presented at VSS 2016