Articulatory suppression and the irrelevant-speech effect in short-term memory: does the locus of suppression matter?

Immediate serial recall for letter sequences was impaired when irrelevant speech (IS) was presented throughout stimulus input and a subsequent rehearsal interval. This irrelevant-speech effect was eliminated when participants engaged in articulatory suppression (repeated articulation of one or more digits) during stimulus input but not when suppression occurred during the postinput rehearsal period. Also, changing-state suppression (articulation of multiple items) impaired the overall level of performance more than did steady-state suppression (repetition of a single item), whereas both forms of suppression had the same influence on the IS effect. Our results suggest that the locus of suppression (during or after stimulus input) may have contributed to discrepant findings in the prior literature regarding the influence of articulatory suppression on the IS effect. We consider the implications of our findings for three prominent models of immediate memory: the working memory model, the object-oriented episodic record model, and the feature model.