Memory for visually presented items is impaired by speech that is played as an irrelevant background. The paper presents the view that changing state of the auditory material is an important prerequisite for this disruption. Four experiments studied the effects of sounds varying in complexity in an attempt to establish which features of changing state in the auditory signal lead to diminished recall. Simple unvarying or repetitive speech sounds were not sufficient to induce the irrelevant speech effect (Experiment 1): in addition, simple analogues of speech, possessing regular or irregular envelopes and using a range of carriers, failed to imitate the action of speech (Experiment 2). Variability of between-utterance phonology in the irrelevant stream (Experiment 3) emerged as a crucial factor. Moreover, predictability of the syllable sequence did not reduce the degree of disruption (Experiment 4) suggesting that supra-syllabic characteristics of the speech are of little importance. The results broadly support the idea that disruption of short-term memory only occurs when the speech stream changes in state. It is argued that disruption occurs in memory when cues to serial order based on phonological representations of heard material interfere with the phonological codes of visual origin. It is suggested that cues to changing state of the speech input contaminate those associated with items of visual origin, which are already in a phonological store.

This work was funded by a United Kingdom Economic and Social Research Council Grant to Christopher Miles and Dylan M. Jones. Many thanks to Neil Morris for discussions on the role of spatial encoding in working memory, Nelson Cowan for his erudite comments during the review process, Andy Tattersall for reading and commenting on the entire manuscript, and Kevin Hapeshi for his programming expertise.

This series of experiments was performed to verify Cowan and Barron's (1987) reported effect of auditory color-word interference on a visual Stroop task. Extant theory predicts effects of irrelevant speech on visual memory tasks involving immediate, ordered recall of the items. Interference between the two sources of information (visual and auditory) is assumed to be located at the phonological store component of the articulatory loop. Perceptual tasks such as the Stroop task, which do not require use of the articulatory loop for rehearsal purposes, should not be similarly susceptible. The present data fail to replicate Cowan and Barron's findings, and are thus consistent with contemporary theory.In a recent study, Cowan and Barron (1987) examined the effects of auditory color-word interference on a visual Stroop task requiring a spoken response. Their results reflected the action of cross-modal interference, suggesting that subjects were unable to prevent the processing of irrelevant, spoken color items. The authors further interpreted their data in terms of a processing system in which multiple verbal items enter a prespeech buffer with a selection mechanism that examines the buffer items in parallel.The present paper further examines the possibility that subjects are unable to prevent the processing of irrelevant, spoken color items, but from an alternative theoretical stance, which is outlined below. Three experiments are reported, each providing evidence suggesting that irrelevant, spoken color items do not interfere with the visual Stroop task. Thus, the notion of cross-modal interference within this paradigm is rejected.Irrelevant or unattended speech impairs immediate, ordered recall of visually presented items, and the effect is exaggerated when the degree of phonological similarity between the auditory and the visual stimuli is high (Salame & Baddeley, 1982). This finding has been interpreted as reflecting the action of a phonological store (PS) and an articulatory control process (ACP), which together form the articulatory loop component of working memory (see Baddeley, 1986, for a review). Briefly, the proposed mechanisms act as follows: Material may be registered in the PS either directly, through auditory presentation, or indirectly, when the ACP is used to convert a visual item into the appropriate phonological code. When a sequence of items is presented visually for immediate serial Part of this research was funded by a United Kingdom Economic and Social Research Council grant awarded to the first and third authors. Adrian Britten collected the data in Experiments la and lb. Address correspondence to Christopher Miles, School of Psychology, University of Wales College of Cardiff, P.O. Box 901, CardiffCFI 3YG, U.K. 77recall simultaneously with irrelevant auditory information, impairment occurs because the unattended (irrelevant) auditory items gain obligatory access to the PS. Because the PS is used to help retain the visually presented items, interference is observed between the two sets of phono...

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