A visual memory may contribute to perception by providing a source of hypotheses against which current input is tested. To make this contribution it should neither require active processes for its maintenance nor be overwritten by subsequent visual events. There is little evidence for a visual memory with these characteristics. However, the single-item visual recency effect observed in the continuous binary decision task is an isolated instance of a short-term visual effect which does not reflect an active visual memory. The present experiments demonstrate that the visual memory underlying this effect possesses the above characteristics. Visual effects were isolated by using single letters varying in case. It was found that visual facilitation can survive an intervening visual event if it is predictable that this event will not be visually identical to the preceding stimulus or if it occurs in a different spatial location. This visual memory appears to retain the last of a particular class of events rather than the last item per se, indicating that the usual limitation of visual facilitation to one item is not due to interference or to decay with time. Further experiments confirmed the automatic nature of the visual facilitation effect and provided evidence for an underlying process which compares current input against memory for preceding stimuli, and directly primes response selection. The final experiments employed photographs of real objects and isolated a two-dimensional visuo-spatial code from an object level code. Only the former is sensitive to the predictability of occurrence of an irrelevant visual stimulus, suggesting that visual memory and perception interact at the level of this code.
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