Semantic inhibition of ignored words during a figure classification task.

Two experiments investigated inhibitory processes in visual spatial attention. In particular, factors influencing the suppression of ignored visual stimuli were investigated. Subjects responded to geometric shapes while distractors were presented in the periphery. Distractors consisted of a single word, a pair of unrelated words, or a single word paired with a string of non-linguistic symbols. Semantic processing of the ignored words was measured with a subsequent lexical decision task. Test probes presented after the prime displays revealed suppression effects for words semantically related to a previously ignored word, but only for conditions in which two distractor words were presented. Suppression was not observed when the prime consisted of a single word or a single word paired with non-linguistic symbols. In Experiment 2 two different time delays between the onset of the primes and the onset of the test probes were used. At the shorter interval facilitatory priming was observed, while at longer intervals suppression was observed. The facilitation-suppression pattern suggests that ignored items are recognized before being suppressed. In summary, the results suggest the following: (1) that selectively attending does not restrict ignored items from gaining access to their semantic representations, and (2) that inhibition is an important process in determining the focus of attention. These results are discussed within a selective attention framework in which all items in a display gain access to memory representations, and attention to selected items causes competing items to be inhibited.