Effect Of Response Range On Performance Estimation In Heading Perception From Optic Flow

Previous researchers found in some studies on self-motion direction perception based on optical flow that people would obviously show a tendency of center bias when judging their own motion direction by using optical flow information.However,other studies show the exact opposite centrifugal bias.To our knowledge,no researchers have looked at the reasons behind these different results.Therefore,in this paper,we conducted four experiments to explore what factors(e.g.,velocity pattern of stimulus,response tool,range of response interval,and motion consistency of optical flow stimulus)lead to bias in direction perception.Experiment 1 systematically explored whether the different results were caused by the different stimulus speed patterns or the different response modes.In each experiment,the duration of optical flow stimulation was 500 ms,and its direction was presented randomly from the interval of [-33°,33°] with an interval of 6°.Participants in the negative direction were simulated to move in the left direction,while participants in the positive direction were simulated to move in the right direction,and0° was the direction directly in front of the body.We set two speed modes presented by the optical flow stimulation: uniform motion mode of 1.5m/s and variable speed motion mode with an average speed of 1.5m/s.The reaction mode was set as a horizontal line with an angle of 80°and a circle with a two-dimensional angle of 360°.Participants reported direction by moving a mouse-controlled probe in the online response mode and perceived direction by pressing a keyboard in the circular response mode.The results showed that the participants still showed a center bias when judging their own direction of movement in the online reaction mode,but showed a centrifugal bias trend in the round reaction mode.In experiment 2,we reset the reaction tool of participants,requiring participants to indicate their perceived direction by clicking the mouse in both reaction modes and adding an arc reaction mode.The optical flow speed was set at uniform speed,and other conditions were the same as in experiment 1.The results showed that participants still showed a center bias trend in the online and circular reactions,and a centrifugal bias trend in the circular reactions.On further analysis,we found that it was not the display of responses that really caused the difference in participants’ responses,but the range of responses that was the most important factor.The larger the reaction range,the more likely the participants were to have the tendency of centrifugal deviation.At the same time,the difference of response tools also affected the accuracy of participants’ judgment.In experiment 3,the results of experiment 2 were further studied by manipulating the reaction range on the arc.We set three arcs with different ranges of 80°,160° and240°.The results showed that the larger the range of responses,the more participants tended to perceive the direction of their own movement away from the center of the screen.In experiment 4,we conducted the study at 100%,80%,and 60% optical flow motion consistency levels.Participants responded on a line with a maximum visual field of 142° and a circle with a maximum visual field of 360°.The results show that with the decrease of optical flow information reliability,the tendency of participant center bias becomes stronger and stronger.This suggests that the direction in which our bodies are directly in front of us still significantly affects our perception of the direction in which we are moving.In summary,it is found that the velocity mode of optical flow stimulation does not affect the type of deviation in the direction perception process based on optical flow,and the response range is the biggest factor affecting the occurrence of different results.The larger the response range,the more likely the participants were to show the tendency of centrifugal deviation.When the response range was smaller,participants showed a tendency to center bias.However,when the consistency of optical flow stimulation decreased,people were still more willing to believe the direction directly in front of the body,showing a tendency of center bias,which indicates that Bayesian model still plays an important role in the process of direction perception.