摘要：AbstractThe passage of time is inseparably linked to any subjective experience, but time cannot be perceived itself. Since humans lack a sensory organ for time, time perception is constructed based on the percepts of the existent senses, such as lights or tones. Biases in these percepts can lead to biases in temporal perception, which explains why subjective time not always matches objective time. For instance, the number of perceived (and not the objectively presented) changes in an event affects the perception of duration. Currently, it is unknown at which stage of cognitive processing sensory input affects subjective time perception. It could be that time perception is based on early sensory processing and that the same areas that encode a stimulus’ sensory properties, also encode its duration. Alternatively, time could be processed by a central, modality-independent clock, which receives input from sensory processing, but is not directly related to it.In a previous experiment, we showed that only the conscious perception of flicker, but not its sensory processing affected perceived duration. However, it is yet unknown whether the flicker affects perceived duration at the perceptual level (during the presentation of the stimulus), or at the response level (after the end of the stimulus). To address this question, we measured participants’ electroencephalogram (EEG), while they were presented with flickering and static stimuli of varying durations. We used a bisection task, in which participants had to judge whether a stimulus was long or short as compared to two previously memorized reference durations. We analyzed the event related activity during the perceptual encoding of the stimulus, to test whether it contains activity related to the subjective perception of time. Any effect occurring in the event related potential (ERP)beforethe time at which the participant could make a decision (“short” or “long”) should reflect a perceptual effect of the flicker on subjective duration.We show that the flickering stimuli, which were judged as lasting longer compared to static stimuli, elicited enhanced negativity in the EEG signal during stimulus encoding. This negativity has previously been characterized as a marker of subjective duration perception, also termed contingent negative variation (CNV). The amplitude of the CNV measured during stimulus encoding predicts the temporal judgment of the participant, showing that the effect is already present at the perceptual level.
