Tachistoscopic experiments have led educators to embrace the 'whole-word' method of reading instruction, consumers to fear the dangers of 'subliminal advertising', and psychoanalysts to believe that repression and primary-process mentation is demonstrable visual phenomena. The "persistence" of visual impressions makes them briefly available for processing even after the stimulus has terminated. This stage of cognition is here called "iconic memory". If iconic storage is a process in the visual system, its duration should depend on visual variables like intensity, exposure time, and post-exposure illumination. Acuity judgments take time, and would be facilitated by prolonging the useful life of iconic storage. A bright post-exposure field is necessarily superimposed on, and combined with iconically-stored information, making it less legible. To the extent that tachistoscopic performance depends on verbal coding-and this is a very substantial extent-an accurate report of the whole pattern is possible only if the subject can complete a verbal description of it before the icon has faded.