An original stimulus (OS) containing three letters in a three by three matrix was briefly presented and followed, after various interstimulus intervals (ISIs), by an interpolated stimulus (IS) containing mask patterns. The exposure of IS impaired severely both position and identity recalls when ISIs were shorter than 20 ms. At longer ISIs, mere exposure of IS did not impair recall of OS, but, if the subjects were asked to make the recall, recognition, or reversal recall of IS before the recall of OS, these tasks caused the selective loss of position information of OS. The results suggested that visual backward masking originates in iconic storage, and visual retroactive interference originates in retrieval process from the visual short-term store.
