Quickly Fading Afterimages: Hierarchicaladaptations Inhuman Perception

Afterimages result from a prolonged exposure to stillvisual stimuli. Theyare best detectable when viewed against uniform backgroundsand can persist for multiple seconds. Consequently, the dynamics of afterimages appears to be slow bytheir verynature. To the contrary, we report here that about 50% of an afterimageintensitycan be erased rapidly—within less than a second. The prerequisite is that subjectsview a rich visual contentto erase the afterimage; fast erasure of afterimages does not occur if subjects view a blank screen. Moreover, we find evidence that fast removal of afterimages is a skilllearned with practiceasour subjects were always more effective in cleaning up afterimages in later parts of the experiment. These results can be explained by a tri-level hierarchy of adaptive mechanisms, as has been proposed by the theory of practopoiesis.