Temporal processing underlying transient twinkle perception in luminance and chromatic stimuli

Humans can detect transitions of frequencies between two sequentially presented flickering stimuli, even when the two flickering stimuli appear steady, a phenomenon known as transient twinkle perception (TTP). A previous study of TTP has suggested that a temporal integration model with a monophasic Gaussian filter can account for this effect. However, the low-level temporal integration of the human visual system for luminance stimuli has been characterized by a biphasic filter. Here, we measured TTP magnitude under various conditions and evaluated Gaussian and bi-phasic filter models. In Experiment 1, we examined the effect of frequency differences between the first and second epochs on TTP magnitude. Experiments 2 and 3 introduced intermediate frequency frames to gradually transition between flickering frequencies. Experiment 4 assessed TTP magnitude using equiluminant chromatic stimuli. Results showed that, for luminance-based TTP, the bi-phasic filter model better accounted for TTP magnitudes, whereas the Gaussian filter model aligned more closely with TTP magnitude observed in the equiluminant chromatic condition. These findings suggest that both luminance and chromatic TTP are natural outcomes of the temporal integration in low-level visual processing and that an ad hoc model for TTP is unnecessary.