Abstract
Critical fusion frequency (CFF) gives a limit of our temporal visual processing; we cannot distinguish a stimulus flickering at a frequency above CFF (~60 Hz) from a stationary one (with the same subjective luminance) if they are presented simultaneously at different locations. When they are presented sequentially at the same position, however, a transient "twinkle" can be perceived (van Diepen et al., 2010). We assume that this "Transient Twinkle Perception (TTP)" is brought by the mechanism for detecting luminance change that is valid even above CFF. The purpose of the present study is to test this. In the experiment, donut-like stimuli (outer diameter: 4 deg, hole diameter: 2 deg) having a sinusoidal luminance profile were presented on a uniform background (50 cd/m[sup]2[/sup]). Six participants were asked to discriminate TTP condition (sequential presentation of stationary and flickering stimuli) from no TTP condition (stationary stimulus only) by temporal 2-AFC. Maximum luminance of the stationary stimulus was fixed (65 cd/m[sup]2[/sup]) while that of the flickering stimulus was manipulated; we prepared six luminance values of the off frame (50 – 62.5 cd/m[sup]2[/sup]), and luminance of the on frame was calibrated by PEST for each participant to equalize the visibility between two stimuli. Temporal frequency of the flickering stimulus was also manipulated by choosing the vertical sync of the CRT monitor from 140, 150, and 170 Hz, and thus flicker frequency was either 70, 75, or 85 Hz. Participants could discriminate TTP from no TTP conditions in every temporal frequency condition, but correct rates were decreased as the luminance of off frame was increased (i.e., the luminance gap between on and off frames decreased). These results suggest that our visual system can detect transient luminance change above CFF, together with TTP is brought with a sufficient luminance gap between flickering and stationary stimuli.
Meeting abstract presented at VSS 2013