A series of studies addresses the possibility that tones disrupt serial recall of visually presented material in the same way as speech. A stream of changing tones is as disruptive of visual serial recall as 4 syllables (Experiments 1 and 2). Similar effects were also shown with a repeated syllable that changed only in pitch (Experiment 3). Just as for speech, the effect of tones is not at encoding but during storage of the serial lists (Experiments 4 and 5). The results suggest that speech and tones are equipotent in their capacity to disrupt short-term memory. A "blackboard" model of working memory to account for the effects is outlined.It is by now well established that background speech interferes with serial recall of visually presented materials

The phonological store construct of the working memory model is critically evaluated. Three experiments test the prediction that the effect of irrelevant sound and the effect of phonological similarity each survive the action of articulatory suppression but only when presentation of to-be-remembered lists is auditory, not visual. No evidence was found to support the interaction predicted among irrelevant speech, modality, and articulatory suppression. Although evidence for an interaction among modality, phonological similarity, and articulatory suppression was found, its presence could be diminished by a suffix, which is an acoustic, not a phonological factor. Coupled with other evidence--from the irrelevant sound effect and errors in natural speech--the action attributed to the phonological store seems better described in terms of a combination of auditory-perceptual and output planning mechanisms.

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Irrelevant sound tends to break through selective attention and impair cognitive performance. This observation has been brought under systematic scrutiny by laboratory studies measuring interference with memory performance during exposure to irrelevant sound. These studies established that the degree of interference depends on the properties of the irrelevant sound as well as those of the cognitive task. The way in which this interference increases or diminishes as characteristics of the sound and of the cognitive task are changed reveals key functional characteristics of auditory distraction. A number of important practical implications that arise from these studies are discussed, including the finding that relatively quiet background sound will have a marked effect on efficiency in performing cognitive tasks.

Irrelevant background speech disrupts serial recall of visually presented lists of verbal material. In 4 experiments, the hypothesis that this disruption is due to the phonological similarity of the irrelevant sound and the list to be recalled was tested. In Experiment 1, item length was controlled and a large irrelevant speech effect was found, but the effect of phonological similarity was small and confined to recency. In Experiment 2, words in the irrelevant stream were used, and the experiment showed an irrelevant speech effect in which phonological similarity played a small part. Experiments 3 and 4 found that similarity (rhyming) within the irrelevant sound stream decreased the level of disruption, and the effect was more marked when the visually presented lists contained items that did not rhyme with one another. Rather than supporting a phonological similarity hypothesis, the results support a changing state hypothesis.

Typically, serial recall performance can be disrupted by the presence of an irrelevant stream of background auditory stimulation, but only if the background stream changes over time (the auditory changing-state effect). It was hypothesized that segmentation of the auditory stream is necessary for changing state to be signified. In Experiment 1, continuous random pitch glides failed to disrupt serial recall, but glides interrupted regularly by silence brought about the usual auditory changing-state effect. In Experiment 2, a physically continuous stream of synthesized vowel sounds was found to have disruptive effects. In Experiment 3, the technique of auditory induction showed that preattentive organization rather than critical features of the sound could account for the disruption by glides. With pitch glides, silence plays a preeminent role in the temporal segmentation of the sound stream, but speech contains correlated time-varying changes in frequency and amplitude that make silent intervals superfluous.Irrelevant background speech disrupts serial short-term memory for material presented visually (see D. M. Jones & Morris, 1992, in press, for reviews). A reasonably clear picture of the features of the task and of the speech that elicits this effect is now emerging, as are the general implications for our understanding of attentional factors in memory (see D. M. Jones & Broadbent, 1991). Two views of this disruption are contrasted here. One is that the extent of disruption depends on the degree to which the sound resembles speech. Salame and Baddeley (1989) have proposed that the effects of speech and nonspeech sounds on serial recall could be understood in terms of a filter or detector system that selectively passes into memory sounds that resemble speech. We wish to put forward an alternative model, the changing-state hypothesis, whose pivotal feature is that the sound has to show particular variation over its time course (see D. M. Jones, in press). Our primary concern in the present paper is to refine the notion of change within the auditory changing-state concept; our secondary purpose is to assess the view that sound has to be "speech-like" before it disrupts serial recall. The purpose of the experimental work reported here is to identify cues common to speech and nonspeech stimuli that nevertheless may serve as the basis for disruption. Specifically, interest is attached to the role of segmentation in signifying changing state, and to the ways this may lead to disruption of recall by both speech and Thanks are due Richard Blight for his general help in setting up the equipment. Helen Bowman and Craig Steel ran some of the subjects.

Evidence for effects of changed environmental context on recognition has been equivocal. Using 3 experiments, the author investigated the role of environmental context from a dual-processing approach. Experiment 1 showed that testing word recognition in a novel context led to a reliable decrement but only for recognition accompanied by conscious recollection, with familiarity-based recognition judgments being unaffected. This was replicated in Experiment 2 using stimuli that were novel to the participants (nonwords). Experiment 3 showed that the decrement in recollection also occurred when the changed-context condition involved presenting items in a different but familiar context. The results suggest that effects of environmental context will only be found when recognition is accompanied by conscious recollection and that this effect is due to a specific item-context association.

Double agency theories of short-term memory posit the functional independence of a phonological store (inner ear) and articulatory process (inner voice). A series of 5 experiments challenges this view. Articulatory suppression during retention of 9-item lists gives rise to a changing-state effect similar to that shown for irrelevant speech. Also, vocalized suppression is more disruptive than silently mouthed suppression, but this difference arises from vocalization itself rather than from any auditory feedback to which it gives rise. Class similarity between the to-be-remembered items and the articulatory material is not a critical determinant, but the effect occurs only with tests of serial order. For mouthed suppression, the irrelevant speech effect is only attenuated with changing-state suppression. Also, the presence of changing-state irrelevant speech abolishes the changing-state effect of articulatory suppression. Functional equivalence of codes from auditory, visual, and articulatory sources is claimed.