Abstract
Purpose Previous studies have reported that our perception of time is modulated during or just before or after eye movements. When two events occur within a very short interval before saccadic eye movements, the order of them is perceived inversely (Morrone et al., Nat Neurosci, 2005). This phenomenon indicates that we perceive events which occur according to time neither in real time nor predictively at the moment. Here, we examined what types of saccades induce the phenomenon, which enables to investigate the key factor of retrospective perception, i.e. ‘postdiction’. Methods We presented two brief bars that marked intervals between 40 and 130 ms just after the saccadic trigger and asked participants to judge their order. There were two conditions of the trigger (CNG and OFF conditions). Under the CNG condition, both fixation square and saccadic target were presented throughout the trial. Participants made a saccade when the fixation square became a circle. Under the OFF condition, the fixation point disappeared and the saccadic target appeared at the same time. The automaticity of the saccades should be higher under the OFF condition than under the CNG condition because visual grasp reflex would have occurred when the saccadic target appeared. We also manipulated the duration between the presentations of the bars and the saccadic trigger between two conditions because the saccadic delay was longer under the CNG condition than under the OFF condition. Results The trials in which the mean of the time points of two bars was 100 ms or less before saccadic onset were analyzed. Proportion correct was above chance only under the CNG condition. Conclusion When the saccadic trigger caused visual grasp reflex, error rate of the temporal order judgment increased. Our results suggest that automaticity of saccades involve the modulation of time perception.
Meeting abstract presented at VSS 2013