Phonological loop and intermittent activity: A whistle task as articulatory suppression.

Abstract

Abstract The purpose of this study was to examine whether the of articulatory suppression is due to the activation of an irrelevant phonology or to intermittent articulatory movements. In the first experiment, subjects were tested for serial recall of visually presented letter sequences that were either phonologically similar or dissimilar, and had to remember each of the letter sequences under a no-suppression control or a suppression condition. In the suppression condition, half of the subjects were engaged in an intermittent speech suppression and the other half were in an intermittent whistle suppression task. The similarity effects appeared in the control condition, but not in the suppression condition, irrespective of the type of suppression. In the second experiment, the similarity again disappeared in the intermittent whistling condition, but not in the condition in which the subjects required to engage a continuous whistling task. The results suggested that the of articulatory suppression was due to intermittent articulatory activity rather than the activation of an irrelevant phonology. Our ability to recall a sequence of items is greatly affected by the characteristics of the items. For instance, phonologically similar sequences of consonant letters lead to poorer serial recall than dissimilar ones. This is the so-called phonological similarity effect (Conrad & Hull, 1964), which indicates the importance of the role played by coding in short-term memory. Additional evidence of coding has been accumulated in studies of articulatory suppression. In this method, the subject is required to repeatedly articulate some irrelevant speech sound such as the word hiya or the. The similarity is abolished by articulatory suppression when the material is presented visually (Besner & Davelaar, 1982; Murray, 1968; Peterson & Johnson, 1971; Wilding & Mohindra, 1980). With auditory presentation however, the similarity withstands articulatory suppression (Levy, 1971; Murray, 1968; Peterson & Johnson, 1971). To account for these results, Baddeley (1990) introduced the idea of a loop (originally, an articulatory loop; Baddeley, 1986; Baddeley & Hitch, 1974) as a subcomponent of working memory. The loop comprises a store and an articulatory control process. The similarity is due to the operation of the store. Auditory information has direct access to this store, but visual information only has access through the articulatory control process, which allows visually presented material to be phonologically coded. Articulatory suppression would simply serve to prevent visual information from entering store. Thus, in visual presentation, when the operation of the articulatory control process is prevented by articulatory suppression, the similarity disappears. Articulatory suppression is a task which requires the subjects to utter a speech sound. Therefore, this activity includes at least the following components: The intention to speak, speech programming, actual articulation, and auditory feedback. Which component of articulatory suppression interferes with the articulatory control process? Recent research has indicated that attentional demands of speech (Saito, 1993b), actual articulation (Baddeley & Wilson, 1985; Saito, 1997), and auditory feedback (Gupta & MacWhinney, 1995; Saito, 1993c) are not major components of the articulatory suppression effects. Rather, the articulatory control process would depend on some form of speech motor programming or planning at a central level (Baddeley, 1990; Waters, Rochon, & Caplan, 1992), and the operation of that process must be disturbed by articulatory suppression acting on speech motor programming (Saito, 1993a, 1994, 1997). …