Visible persistence in transient random dot stimuli
43.321, Monday, May 13, 8:30 am - 12:30 pm, Royal Ballroom 6-8
Kathrin Thaler1, Maximilian Bruchmann1; 1Institute of Biomagnetism and Biosignal Analysis, University of Muenster, Germany
Visible persistence (VP) is defined as the prolonged percept of a visual stimulation continuing after the physical termination of the physical stimulus itself. In the past, great effort has been spent investigating VP of stimuli with minimal physical duration. In this study, we created a novel kind of visual stimulus consisting only of a single transient luminance signal, and thereby examined an extreme case of minimal duration. In two experiments subjects were repeatedly shown two successively presented random dot matrices. Both matrices consisted of 1024 ✕ 768 randomly placed black and white pixels. On the transition from one array to the second, all pixels within a certain area reversed luminance polarity. Phenomenologically, the reversal produces the percept of an object (shaped like the area within which the pixels polarity was changed) with an abrupt onset and a gradual decline. We measured VP duration of these transient shapes by asking subjects to match the onset of an auditory or visual reference stimulus to the onset and offset of the perceived shape. To explore the influence of spatial parameters on VP we presented annuli as transient shapes in our first experiment. The annuli were presented centrally and varied in size (inner radius) and thickness. VP increased with stimulus size and decreased with annulus thickness, suggesting that retinal position as well as the size of the surface area may influence VP. Thus, in a second experiment, we systematically varied the eccentricity and the radius of transient discs. The results show in interaction of size and eccentricity, indicating a non-monotonic relationship between spatial parameters and VP. We conclude that in order to explain VP durations, spatio-temporal receptive field properties but also higher-level mechanisms, especially filling-in, have to be taken into account.