Abstract
We find that adaptation to twinkle or flicker slows down the perceived rate of twinkle, flicker, and motion. Twinkle adaptation. Observers adapted to a field, 11° wide x 22° high, of twinkling dynamic random noise, namely black/white random dots (6 minarc diam) that refreshed with spatially uncorrelated dots 27 times per second. They then viewed random test dots that twinkled at rates between 8 and 27 fps on different trials. Result: a matching method showed that the test dots now appeared to twinkle at half their actual rate. Observers also adapted to a random-dot pattern that flickered in counterphase, alternating between its own positive and negative 27 times per sec (13.5 Hz). After this adaptation, a fresh field of test dots that counterphased at 4 to 13.5 Hz appeared to flicker at about half its actual rate. We attribute these results to visual filters tuned to different temporal frequencies, with spatial resolution able to resolve the fine-grain random dots. Flicker adaptation. Following adaptation to a spatially uniform rectangle that flickered between black and white at 13.5 Hz, a congruent uniform test rectangle flickering at 4 to 13.5 Hz appeared to fall to 70% of its actual flicker rate. We attribute these results also to temporally tuned visual filters, but of undetermined spatial resolution. Cross-adaptation. Adapting to 27 fps twinkle caused test random dots that drifted at speeds between 0.25°/s and 3°/s to slow down perceptually to 60--80% of their actual speed. Possibly, twinkle contains apparent movement in all directions that adapt all motion sensors. Similarly, adapting to 13.5Hz spatially uniform flicker also reduced perceived test speeds to 80% of their actual speed. This implies that prolonged viewing of flicker leads to adaptation of the temporal, not spatial, components of the test motion.
Meeting abstract presented at VSS 2013