Investigation On The Mechanism Of Time Perception Of Biological Motion And Nonbiological Motion

Accurate time processing is crucial for people's daily activities.However,there is no specific sensory receptor in the nervous system,and perceived duration varies with external inputs.There is information entering into the perceptual system all the time.The change and movement of object are important factors influencing subjective time perception,because the constant change of visual landscape can index the passage of time.Distributed,specialized mechanisms exist in the brain to monitor the temporal behavior of moving objects.One such specialization of particular importance is related to the animacy or biological nature of the objects.Previous studies have shown that time perception and motor timing are influenced by animacy:The observation of a biological movement performed by other people may bias the timing of a motor act or the judgement of perceived duration of an event,but little is known about the relevant cognitive mechanism.Through eight experiments,the current two studies examined(1)whether mental simulation accounted for the bias in time perception of biological motion and(2)whether global configurational information or local kinematic information of the objects(human point-light figures)was responsible for the bias.The motor resonance theory assumes that when we see someone moving,our brain tends implicitly simulate the observed action.The results of Graf et al.(2007)supported this hypothesis and proposed the concept of mental stimulation.Therefore,in Study 1,we argued the neural mechanism for time perception used by the brain to process visual motion is calibrated against the specific predictions based on mental stimulation regarding biological motion.We used a variant of the occlusion paradigm of Graf et al.(2007)to separate the mental simulation process from the perception of biological motion.In order to prove that subjective duration estimation in the occlusion paradigm is related to mental stimulation,Experiment 1 introduced a temporal shift(earlier,on time,or later)to the final posture of the human point-light figure acting five different movement and compared the subjective estimation of occlusion duration under three moving gap conditions.The result showed subjective duration estimation gradually increased with increasing movement gap,and indicated that subjective duration estimation in the occlusion paradigm was related to mental stimulation.To exclude the effect of different biological movement sequence on the subjective duration estimation in Experiment 1,Experiment 2 only compared the subjective duration estimation of the occlusion under a biological motion and its corresponding nonbiological motion conditions.The results showed the bias in time perception of biological motion still existed in the occlusion paradigm.Based on the results of Experiment 1 and Experiment 2,Experiment 3 explored whether the differences in time perceptions between biological and nonbiological motion were due to expectations based on mental simulation of biological motion.The results showed mental simulation of biological motion was responsible for the bias in time perception of biological motion.However,the nonbiological movement sequence in Experiment 3 was manipulated based on biological movement sequence.Participants might still have a mental stimulation under nonbiological condition,but the mental stimulation of biological motion is easier and more obvious than nonbiological motion.Experiment 4 changed the speed of the human point-light figure before occlusion and the results ruled out this possible explanation.The results of above experiments came to the conclusion that there was significant mental stimulation in time perception of biological motion rather than nonbiological motion and the interference of unrelated variables was also controlled under nonbiological motion condition,but the nonbiological motion seemed to be a random movement of scattered dots.The reason that participants were unable to perform mental simulations and expectations might be due to randomization rather than lack of animacy.For this reason,Experiment 5 used the small translational square,which was commonly used in duration estimation experiments in the non-occlusion paradigm as experimental stimuli in the occlusion paradigm and the speed of the square before occlusion was also changed.The results showed that the subjective duration estimation of the occlusion prolonged with increasing speed,indicating that mental stimulation did not exist in the time perception of typical movement of small square.So.the mental simulation was not the basis of time perception of nonbiological motion.What was the mechanism of time perception of nonbiological motion?Based on representational momentum,the researchers hypothesized that the duration estimation of nonbiological motion was based on the expectation of visual extrapolation of its motion trajectory.In order to verify this hypothesis,Experiment 6 compared subjective duration estimation of occlusion under the condition of the presence or absence of small square position cues after occlusion.The results showed there was not significant difference between the subjective duration estimation under two conditions indicating duration estimation of nonbiological motion might be based on the expectation of visual extrapolation of its motion trajectory.To further understand the mechanism of time perception of biological motion,Study 2 still used the variant of the occlusion paradigm to explore whether global configurational information or local kinematic information of the objects(human point-light figures)was responsible for the bias and whether mental simulation accounted for the role of such information.Experiment 7 compared the subjective estimation of occlusion duration under three conditions:normal human point-light movement,global human point-light movement(by maintaining the global configurational information but changing local kinematic information),and local human point-light movement(by maintaining the local kinematic information but randomizing global configurational information).The results showed that the bias in time perception of biological motion still existed in the normal and local human point-light movement conditions,but not in the global movement condition,suggesting that local kinematic information was sufficient to elicit time perception bias in biological motion.Experiment 8 aimed to explore whether mental simulation was responsible for the bias in time perception of biological motion by introducing a temporal shift(earlier,on time,or later)to the final posture of the human point-light figure.The results showed that mental simulation of local kinematic but not global configurational information was responsible for the bias in time perception of biological motion.In summary,based on the results of Study 1 and Study 2,this research came to following conclusions:1.time perception of biological motion was based on mental simulation of local kinematic information,and the mechanism was unique to biological motions;2.the basis of time perception of nonbiological motion was not mental simulation,but might be the expectation of visual extrapolation of its moving trajectory.Understanding the mechanisms of time perception of biological motion helps us understand how people interact with each other accurately.