The perceived position of a moving object is not the result of position integration

The flash-lag effect is a robust visual illusion in which a flash appears to spatially lag a continuously moving stimulus, even though both stimuli are actually precisely aligned. Some research has been done to test how visual information has been integrated over time. The position integration model suggests motion integration is a form of interpolation of past positions, and predicts that we cannot perceive the reversal point at its actual position on the trajectory of a moving object which reverses abruptly. In current research, we demonstrate that subjects could perceive the reversal point accurately while the psychometric function measured by a flash does not pass through the actual turning point. These results do not support the position integration model. We propose that the flash-lag effect is more likely to be a temporal illusion.