Different Processing Speed Of Position Information Does Not Contribute To The Flash-lag Effect

Motion perception is one of the most important functions of human visual perception system. How to perceive a moving object and constantly update its positional information has been extensively studied in the past decade, and particularly the flash-lag effect. It is a robust visual illusion wherein a flash and a moving object that appear in the same location are perceived to be displaced from one another. Despite fruitful results in this research field, there still remain lots of arguments on the mechanisms underlying this illusion. Essentially, there are two different explanations: one is the postdiction model, and the second is the different latency model. The latter suggests that the different processing speed of the moving object and flash contributes to the flash-lag effect.The present study is aimed at examining the different latency model. Based on the classical flash-lag paradigm, we adopted two visual events (onset and offset, which have different processing latency) to take the place of the flash, and investigated the flash-lag effect under these two conditions. The results from our three experiments indicate that, (1) the processing speed is significantly higher than that of offset; (2) the flash-lag effect under onset condition is significantly larger than that of offset condition. The results are inconsistent with the different latency model. Thus, we propose a discrete sampling hypothesis to explain the flash-lag effect.