Figure 3

Average across-observers (a) symmetry detection thresholds and (b) difference thresholds calculated as static – speed (or flicker) thresholds. The speed conditions (red symbols) are shown as a function of signal-to-noise speed ratio (lower axis), while the flicker condition is plotted as a function of signal-to-noise lifetime ratio (upper axis). The static condition is represented by the black dashed line in top panel (a), while in bottom panel b (difference from static) it corresponds to zero. The red and blue dashed lines in the top panel (a) represents quadratic functions fit to the speed thresholds (red) and dynamic flicker thresholds (blue). The signal-to-noise ratios, which were calculated as speed (or lifetime) of symmetrical elements divided by speed (or lifetime) of noise elements, are plotted in reverse for the dynamic flicker condition as a larger ratio represents a longer lifetime duration and therefore, a slower rate of change, whereas for the speed condition a larger ratio represents a longer distance travelled and therefore a faster rate of movement. Hence, in order to compare shorter lifetimes with faster speeds, the ratios of signal-to-noise must be plotted in reverse order. Error bars and grey area are ±1 standard error of the mean (SEM).