Verbal working memory as an emergent property of the language production architecture

Maintenance in verbal working memory (WM) has long been thought to be achieved by specialized storage systems that maintain purely phonological representation. An alternative hypothesis is explored in which maintenance in verbal WM is emergent from activation of the language production architecture. A review of the literature reveals similarities between language production and verbal WM, including serial position constraints, phonological similarity effects, and long-term effects of linguistic knowledge. The production-WM relationship is then tested in four studies in which two levels of production planning are manipulated: phonological encoding (studies 1 and 2) lexical-semantic retrieval (studies 3 and 4).;In study 1, a tongue-twister manipulation is employed across four experiments with varying mnemonic (reading, recall and recognition) and output (speaking and typing) demands. Study 2 tests whether the same brain areas responsible for phonological encoding in production underlie the maintenance of phonological representation in WM. Covtert naming tasks are used to elicit brain activation in an FMRI scanner. These brain regions are then targeted for repetitive transcranial magnetic stimulation (rTMS) during production and memory tasks. Results across the two studies show similar error distributions regardless of the mnemonic demands of the tasks, and that stimulation of language production regions deleteriously affects verbal WM.;In study 3, word concreteness and phonological similarity were factorially manipulated within four experiments, across which presentation modality (visual or auditory) and concurrent articulation (present or not) were manipulated. Results showed a consistent interaction whereby the magnitude of the phonological similarity effect was larger for concrete relative to abstract words. In study 4, a novel dual-task paradigm was established. Participants simultaneously engaged in semantic categorization or line orientation tasks while performing delayed serial recall across varying list material (concrete, abstract, and nonwords). Results showed that relative to the line orientation task, semantic categorization decisions increased serial ordering errors for concrete words, but not abstract or nonwords.;The results demonstrate that short-term maintenance occurs over multiple levels of linguistic representation, and suggest there is no need to posit specialized WM systems as the short-term maintenance of verbal information may be nothing more than activation within the language production architecture.