Influence Of Impiled Motion Coherences On Time Perception

Time perception is fundamental for making sense of the dynamic physical world and has been intensively studied.However no such a specific human body organ is existed in charge of time perception.Instead,subjective time perception is influenced by the nontemporal stimulus properties,such as motion.Previous studies showed that the subjective duration of moving stimuli was longer than that the static stimuli.As a counterpart of real motion(RM),a vivid sense of motion can also be inferred from static pictures of objects in motion such as a cup falling off a shelf,a photograph of an athlete running,etc.This perceptual phenomenon is known as implied motion(IM)and reflects the inferred motion from the top-down perceptual processing.Previous literature has shown that the IM and RM might share similar processing mechanisms and both could be explained by the classic internal clock model.In addition,as an important perceptual feature of motion perception,motion coherence also affects the time perception.But this effect will be different by the use of different stimulation materials,experimental paradigms of factors.Consistent reports showed that increased speed of moving stimuli lengthened perceived time duration.However,research has not yet investigated whether global motion information(e.g.,coherence)in IM could modulate the perceptual vividity and distort the subjective time duration.In view of this,this study used behavioral and EEG experimental methods to test whether the coherence of the IM direction affects the time perception.In Experiment 1,we combined the bisection time perception paradigm and our precious IM coherence paradigm,and the point of subjective equality on time perception was used as the behavior index to explore whether IM coherence will affect subjective time perception,the Experiment 1 used a mixed design of 2 stimulation types(IM / non-IM)× 4coherence levels(0% / 50% / 75% / 100%).This task included a training phase followed by a test phase.Participants needed to make a duration judgment.Results indicated that IM images were perceived to be presented for longer than non-IM images,that is,the subjects’ sensitivity to the time perception of IM information became higher.And the observation that the perceived duration of IM lengthened with increased coherence.These findings suggest that varying coherences of IM image increase the perceived duration of the stimulus.Experiment 2 was based on EEG experiments.Based on experiment 1,the internal mechanism was explored.Previous studies on IM also found that the P2 as a key indicator of IM coherence,which could reflect different perceptual processing levels of coherence.Moreover,previous studies have shown another ERP indicator of time perception:contingent negative variation(CNV),which may be related to the neural processing mechanism of time perception.Therefore,Experiment 2 used the same paradigm as Experiment 1,with ERP components P2 and CNV as indicators,tested whether the amplitude of P2 and CNV would be different with the coherence level and the stimulation duration.In line with our prediction,the results of experiment 2 show that:(1)The higher the coherence level of IM with the smaller the point of subjective equality of the individual,the same objective time will be subjectively perceived longer.(2)The higher the coherence level,the smaller the point of subjective equality and the larger the amplitude of P2.(3)Consistent with previous studies,CNV was related to the perceptual processing of objective time,and its CNV amplitude would decreases as the increase of stimulation duration.The above results in Experiment 2 replicated the result in experiment 1,and further confirmed that the IM coherence represented by P2 was a key factor leading to time expansion.To sum up,this study explored whether IM coherence would affect time perception from two aspects of behavior and neural mechanism.Results indicated that IM images were perceived to be presented for longer than non-IM images,and the observation that the perceived duration of IM lengthened with increased coherence.Moreover,the P2 might be a key EEG indicator of IM coherence affecting time perception.Combined with previous studies,this study shows that the coherence level of top-down perceptual stream from IM could influence subjective experience of time perception,and this influence may come from the regulation of the motor perception cortex(h MT +)signal.