Verbal, visual, and spatial working memory demands during text composition

Two experiments examined whether text composition engages verbal, visual, and spatial working memory to different degrees. In Experiment 1, undergraduate students composed by longhand a persuasive text while performing a verbal, visual, or spatial concurrent task that was presented visually. In Experiment 2, participants performed a verbal or spatial concurrent task that was aurally presented. Writing performance was not disrupted differentially across the three tasks. Performance on all concurrent tasks showed fewer correct responses and longer RTs relative to single-task, baseline data. However, the demands on visual working memory were as high as those on verbal working memory, whereas demands on spatial working memory were minimal. The findings help to delineate the roles of the verbal, visual, and spatial working memory in written composition. Composing a text involves at least four major cognitive components. First, planning processes are engaged to prepare the content of the text by retrieving ideas from the writer’s long-term memory and by reorganizing them if necessary. These planning processes also allow the scheduling of writing by preparing action plans for composing (Hayes & Grawdol-Nash, 1996). Second, translating processes grammatically encode the conceptual structure elaborated during planning by retrieving in the mental lexicon the syntactic and morphological properties of this content (Levelt, 1999). Orthographic encoding is further needed prior to handwriting (Bonin, Fayol, & Peereman, 1998; Bonin, Peereman, & Fayol, 2001; Caramazza, 1991). Third, with motor execution processes writers graphically © 2008 Cambridge University Press 0142-7164/08 $15.00 Applied Psycholinguistics 29:4 670 Olive et al.: Working memory in writing transcribe their text. They program their handwriting (or typing) movements and then they execute these movements. Fourth, revision processes (reading and editing) allow writers to compare the segments of the text not yet handwritten or the text already written with their mental representation of the intended text. It is important that these writing processes are not activated linearly. Rather, each process can interrupt any other process at any moment during the composition (Flower & Hayes, 1980). In a recent study, Kellogg, Olive, and Piolat (2007) analyzed the degree to which the verbal, visual, and spatial components of working memory (WM) support the writing processes during sentence production. Consistent with the notion that grammatical, phonological, or orthographic encoding require the use of verbal WM (Chenoweth & Hayes, 2003; Levy & Marek, 1999; Mueller, Seymour, Kieras, & Mueller, 2003), the authors found that writing a definition to either a concrete or an abstract noun slowed the responses made to a concurrent verbal task. They also found that writing definitions of only concrete nouns disrupted the visual task. This outcome is consistent with Kellogg’s claim (1996) that planning the content of the message engages visual WM when the referents of concepts are imaged. The spatial task, which required participants to memorize and to match spatial locations concurrently with writing, was not disrupted for either concrete or abstract nouns. The present research extends these earlier findings to text composition. We reexamine the relationship between the verbal, visual, and spatial components of WM and the writing processes when writers are composing a text. Moreover, because activation of the different writing processes changes throughout a writing session, their demands should also vary. Consequently, we also investigated whether the demands that writing places on the different WM components change across a writing session. The role of WM in text composition has been emphasized since the seminal work of Flower and Hayes (1980), who argued that writers are overloaded when they compose a text because of the heavy demands the activity places on WM. Kellogg (1996) proposed a model of the relationships between writing and WM by adopting Baddeley’s (1986) multicomponent model of WM. Accordingly, WM is conceived as a multicomponent system (Baddeley, 1986). An attentional component, the central executive, regulates and controls information. It is aided by two independent systems: the phonological loop, which is specialized for the short-term storage and processing of verbal and acoustic information, and the visuospatial sketchpad, that temporary holds visuospatial information and that is assumed to be fractionated into two visual and spatial components (Logie, 1995; Smith & Jonides, 1997). In that framework, Kellogg analyzes how the different components of WM systems support the writing process. Several studies have confirmed that the writing processes impose large attentional demands on the central executive. For instance, Kellogg (1987) examined cognitive effort of the writing processes by asking participants to perform, while composing a text, a secondary RT task associated with a directed verbalisation task (see Olive, Kellogg, & Piolat, 2002, for a detailed description of the procedure). Kellogg found that planning and revision processes placed more attentional demands on the central executive than translating processes do. Moreover, it has been shown that planning, translating, reviewing, and transcribing compete with Applied Psycholinguistics 29:4 671 Olive et al.: Working memory in writing one another for the limited attentional capacity of the central executive (Kellogg, 2002). McCutchen (1996, 2000) reviewed correlational and experimental studies showing that during writing development, greater fluency of the writing processes frees WM resources and consequently results in better writing performance. In sum, all high-level writing processes engage the central executive component of WM. They require attention to enable their processing and to coordinate the various demands they pose on WM, but they might also engage some central bottleneck (Pashler, 1994), for example, for coordinating linguistic processes (see Ferreira & Pashler, 2002, for an example in spoken language production). Kellogg (1996) proposed that the writing processes, together with their central executive demands, differently engage the code-specific components of WM (the phonological loop and the visuospatial sketchpad; Baddeley, 1986). Planning processes would require access to the visuospatial sketchpad when writers visualize images and organize diagrams and other visuospatial representations as they plan. By contrast, translating and aspects of reviewing (specifically, reading) would impose demands on the phonological loop. Madigan, Johnson, and Linton (1994) observed that unattended speech, which is thought to load the phonological loop, effectively slowed the writer’s fluency in generating sentences. Levy and Marek (1999) examined this effect more closely by asking participants to formulate sentences using five words. Both normal and scrambled unattended speech reduced the number of words successfully included and increased the number of incorrect changes in number and tense, indicating the disruption depended on the phonological properties of the speech rather than its semantic content. More recently, Chenoweth and Hayes (2003) found that repeatedly saying the word “tap” while producing text suppresses the inner voice that accompanies writing, the texts produced in that condition contain more mechanical errors, and holistic text quality decreases. Thus, there are now several studies supporting the idea that verbal WM is involved in writing when translating content into language, and more precisely to support short-term maintenance of phonological representations. Other findings on dysgraphia also suggest that verbal WM may support the graphemic buffer at least partially (Miceli, Caltagirone, Capasso, Caramagno, Patria, Turriziani, Zampetti, & Caramazza, submitted). Less is known about visuospatial WM in writing. When reading the text, a visual component might be involved (Hayes, 1996). For example, the spatial layout of the text is shown to affect revision of a text (Piolat, Roussey, & Thunin, 1997). Content of the text, and relationship among the objects mentioned in the text, might also be visual features available during writing. For example, Passerault and Dinet (2000) hypothesized that descriptive composition, because it relies on mental imagery, should impose more demands on visuospatial WM. By contrast, they assumed that argumentative text might not requires visuospatial WM when the topic only involves abstract content. To test that hypothesis, they asked participants to compose either an argumentation or a descriptive text while performing a visual concurrent task that consisted in memorizing visuospatial shapes. As anticipated, writers’ fluency was slower when composing the descriptive text than the argumentative one. Lea and Levy (1999) also found that a concurrent visuospatial tracking task affected the fluency of written composition. They showed that the visual concurrent Applied Psycholinguistics 29:4 672 Olive et al.: Working memory in writing task disrupted writers’ fluency by 13% relative to a writing only control condition, whereas a concurrent phonological task disrupted fluency still more (21%) and showed more task errors compared to performance on the visuospatial task. At the same time, the writing task disrupted performance more on the phonological task compared with the visuospatial task, but significant interference was observed for both. By contrast, Kellogg (2004) did not found any effect of a visual concurrent task in sentence generation. This difference in outcomes certainly results from differences in nature of the secondary tasks between the two experiments, but also on the fact that composing a full text, by contrasts with sentence generation, probably poses more visuospatial demands because of processing of the physical layout of the text (Hayes, 1996). Kellogg (1999), however, made specific assumptions on the role of visuospatial WM in text production. He argued that visual WM is engaged when processing figurative material during the idea generation phase of planning, and that spatial WM may be needed when organizing information during planning. Galbraith, Ford, Walker, and Ford (2005) tested these assumptions by asking undergraduate students to compose a text in three distinct phases: generating ideas, organizing ideas with an outline, and producing text. Participants had also to carry out several concurrent tasks throughout the first two phases. Among these tasks, participants monitored a spatial tracking task and a visual noise task. Galbraith et al. (2005) did not find any reliable effect of the visual noise task, suggesting that a purely visual task does not disrupt planning processes. They found, however, that the spatial tracking task affected organization of ideas by reducing quality of content and affecting various aspects of the outline realized before producing text. Spatial demands presumably come from representation of the spatial layout of the text. Several findings in reading research have shown that changes in the layout of the text affect memory for words location, a phenomenon that most of us have already experienced (Lovelace & Southall, 1983; Rothkopf, 1971). A similar phenomenon occurs in writing (Le Bigot, Passerault, & Olive, in press). Moreover, when planning, we generally resort to the spatial layout of the sheet to mark the semantic organization of the text, for example, when paragraphing a text (Bond & Hayes, 1984). Finally, and obviously, handwriting is also a visual– motor integration activity and its visuospatial demands have been investigated (Van der Plaats & van Galen, 1990). For example, when the visual feedback is suppressed during a composition, processing demands of handwriting increase and coordination of the writing processes changes (Olive & Piolat, 2002). Taken together, these findings suggest that the visual or spatial components of WM may be at times needed in text production (particularly during planning), and that verbal WM is most central to text production. The studies that we report here evaluated the specific demands that text composition place on the different components of WM. For this purpose, we manipulated the type of WM task writers had to perform while composing their text. By contrast with most previous studies, we examined verbal, visual, and spatial WM in the same experiment. Numerous lines of evidence now indicate that verbal, visual, and spatial systems can be dissociated in WM. Both behavioral and neuroimaging results indicate that the sketchpad is fractionated into separate visual and spatial components (Hecker & Mapperson, 1997; Logie, 1995; Logie & Marchetti, 1991; Applied Psycholinguistics 29:4 673 Olive et al.: Working memory in writing Sala, Räma, & Courtney, 2003; Smith et al., 1995). The visual component (the visual cache) is a passive system that stores visual information and spatial locations in the form of static visual representation. The spatial component (the inner scribe) is an active spatial rehearsal system that maintains sequential locations and movements and that also serves to refresh decaying information in the visual cache. Our participants composed a text in longhand while concurrently performing visual, spatial, or verbal tasks. The tasks were designed to require the same input (visual, Experiment 1, or aural, Experiment 2), to require the same modality of response and to be minimally disruptive of text composition. Ransdell, Levy, and Kellogg (2002) concluded that disrupting both fluency and text quality requires placing a heavy load on the verbal and central executive components of WM, such as retaining six digits while composing. Because the tasks we used in the present experiment are less intrusive than retaining digits (Kellogg et al., 2007), we anticipated that the primary writing task would unfold with normal fluency and quality. However, achieving this level of writing performance would decrease accuracy and increase reaction time (RT) on the secondary task. We predicted that writing would place more demand on verbal WM because more writing processes draw on verbal WM than on visual or spatial WM. Performance at the verbal task should therefore be lower (long RTs, low accuracy) than on the visual task (short RTs, high accuracy).