Academic journal article Psychologische Beiträge

Effects of Irrelevant Speech and Articulatory Suppression on Serial Recall of Heard and Read Materials

Academic journal article Psychologische Beiträge

Effects of Irrelevant Speech and Articulatory Suppression on Serial Recall of Heard and Read Materials

Article excerpt

Effects of irrelevant speech and articulatory suppression on serial recall of heard and read materials*

Summary

Immediate serial recall of verbal items is severely disrupted when irrelevant background speech is presented during task performance. According to the phonological loop model, this effect occurs because spoken material gains obligatory access into the phonological store, whereas visually presented items must be translated into a phonological code by means of subvocal rehearsal. We tested this assumption by examining the combined effects of irrelevant speech and articulatory suppression on serial recall of digit sequences presented either visually or auditorily. In line with the phonological loop model, articulatory suppression abolished the irrelevant speech effect when presentation was visual. In the auditory presentation condition, the irrelevant speech effect withstood suppression (Experiments 1). Furthermore, Experiments 2, 3 and 4 demonstrated that, irrespective of presentation modality, the irrelevant speech effect persists through a 10 second retention interval filled with articulatory suppression. These results contradict the assumption that phonological traces decay rapidly when rehearsal is prevented by articulatory suppression, but are in line with findings on the persistence of the phonological similarity effect. The results are discussed with respect to recent models of short-term memory.

Key words: short-term memory, working memory, irrelevant speech effect, articulatory suppression, trace decay, modality effects

Introduction

Immediate serial recall of verbal material is severely disrupted by concurrent presentation of background speech which subjects are instructed to ignore. This "irrelevant speech effect" (ISE) occurs even with low intensities of the speech, and with languages that the participants do not understand. With respect to the locus of the interference caused by irrelevant speech, there is convincing evidence that it affects rehearsal, but not encoding and recall of the items (e.g., Miles, Jones & Madden 1991; Baddeley & Salame 1986). The effect has been interpreted within the framework of the phonological loop model proposed by Baddeley (1986, 1990, 1992). The phonological loop is a sub-component of working memory which serves as a storage system specializing in the retention of speech-based material. According to Baddeley's model, the phonological loop consists of two parts. The first is a passive storage component which holds speech-based information in a phonological code which is independent of input modality. The second is an active rehearsal process, based on speech-output mechanisms, which serves to refresh the contents of the phonological store in order to prevent trace decay. Without rehearsal, phonological traces are assumed to decay rapidly after 12 seconds. Additionally, the rehearsal process is necessary for re-coding visually presented items into a phonological code necessary for entry into the store. Conversely, heard (spoken) items are assumed to gain direct access to the phonological store, without the mediation of the rehearsal process.

This model is based on a collection of empirical findings concerning the combined effects of articulatory suppression (concurrently uttering a simple syllable such as "the"), word length (poorer performance for long than for short words; Baddeley, Thomson & Buchanan 1975), phonemic similarity (poorer performance for similar sounding items; Conrad 1964), and irrelevant speech (Salame & Baddeley 1982). When the items are presented visually, blocking the rehearsal process by means of articulatory suppression abolishes the effects of word length, phonemic similarity and irrelevant speech. This is assumed to occur because articulatory suppression prevents visually presented items from being phonologically recoded and registered within the phonological loop. With auditory presentation, articulatory suppression abolishes the word length effect, but leaves the phonological similarity effect unaffected (Baddeley, Lewis & Vallar 1984). …

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