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Sophie Herbst, Amir Homayoun Javadi, Niko A. Busch; How long depends on how fast – perceived flicker frequencies dilate subjective duration. Journal of Vision 2012;12(9):141. doi: 10.1167/12.9.141.
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© ARVO (1962-2015); The Authors (2016-present)
When a stimulus changes over time, its duration is subjectively dilated. It is unknown whether the dilation of dynamic stimuli is caused by automatic processing of the stimulus, or is based on higher level processing that requires conscious awareness of the change. We manipulated stimulus dynamics and their conscious perception by presenting flickering light with frequencies below and above the flicker fusion threshold (i.e. the highest frequency still consciously perceived as flickering). We used LEDs mounted in a custom-built binocular flicker-goggle while recording EEG from 64 electrodes, to stimulate participants’ visual field with light flickering at a broad range of frequencies (8 -166 Hz). By recording steady state visual evoked potentials (SSVEP), we found a range of frequencies, which were not consciously perceived as flickering, but still evoked SSVEP over occipital cortex (45 – 70 Hz). We also assessed subjective duration of the same stimuli in a two alternative forced choice task, in which participants compared the duration of the flickering stimuli to the duration of a static standard stimulus. Our results show that only stimuli that were consciously perceived as flickering were judged longer than the quasi-static reference stimulus. We found an inverse linear relationship between flicker frequency and perceived duration: the extent of overestimation decreased with higher frequencies. However, overestimation disappeared for frequencies above the flicker fusion threshold, even if those frequencies still evoked SSVEP. In conclusion our findings suggest that conscious perception of stimulus dynamics, such as temporal frequency, is driving subjective time dilation.
Meeting abstract presented at VSS 2012
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