Working Memory and Language (Susan E. Gathercole, Alan Baddeley)

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Notes from the book:

"Baddeley and Hitch (1974) identified three components of working memory. The central executive component is the most important. Its functions include the regulation of information flow within working memory, the retrieval of information from other memory systems such as long-term memory, and the processing and storage of information. The processing resources used by the central executive to perform these various functions are, however, limited in capacity. The efficiency with which the central executive fulfils a particular function therefore depends on whether other demands are simultaneously placed on it. The greater the competition for the limited resources of the executive, the more its efficiency at fulfilling particular functions will be reduced."

"The central executive is supplemented by two components which are termed “slave systems”. Each slave system is specialised for the processing and temporary maintenance of material within a particular domain. The phonological loop maintains verbally coded information, whereas the visuo-spatial sketchpad is involved in the short-term processing and maintenance of material which has a strong visual or spatial component. Figure 1.1 provides a simple schematic representation of the working memory model."

"The central executive fulfils many different functions. Some of its primary functions are regulatory in nature: It coordinates activity within working memory and controls the transmission of information between other parts of the cognitive system. In addition, the executive allocates inputs to the phonological loop and sketchpad slave systems, and also retrieves information from long-term memory. These activities are fuelled by processing resources within the central executive, but which have a finite capacity. Cognitive tasks that have been suggested to involve the central executive include mental arithmetic (Hitch, 1980), recall of lengthy lists of digits (Baddeley & Hitch, 1974), logical reasoning (Baddeley & Hitch, 1974), random letter generation (Baddeley, 1966a), semantic verification (Baddeley, Lewis, Eldridge, & Thomson, 1984a) and the recollection of events from long-term memory (Hitch, 1980)."

"The phonological loop is a slave system specialised for the storage of verbal material. It comprises two components, as shown in Fig. 1.3 (Baddeley, 1986). The phonological store represents material in a phonological code which decays with time. A process of articulatory rehearsal serves to refresh the decaying representations in the phonological store and so to maintain memory items. The rehearsal process is also used to recode nonphonological inputs such as printed words or pictures into their phonological form so that they can be held in the phonological store. In contrast, spoken speech information gains direct access to the phonological store without articulatory rehearsal."

"The two-component architecture of the phonological loop is based on a large body of experimental evidence accumulated during the past 20 years. More recently, it has also been supported by studies of neuropsychological patients with deficits that appear to correspond to subcomponents of the loop. The principal experimental phenomena associated with the phonological store and the rehearsal process are summarised below."

"THE CENTRAL EXECUTIVE
...two general cognitive resources in working memory—storage space, which is the space available for storing the products of perceptual-cognitive processing, and operating space, which consists of the pool of resources available for carrying out intellectual operations. Total processing space consists of the sum of storage and processing space."

"THE SKETCHPAD
...we know that before the age of about seven years, young children do not use the phonological loop to store the names of picture lists. Nonetheless, four- and five-year-old children can typically remember a sequence of two or three pictures.
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"The working memory model has proved to be a very useful tool in guiding analysis of the developmental changes in short-term memory function during childhood. All three principal components of working memory appear to be present at the youngest age at which short-term memory is typically tested, four years. At this age, children appear to retain auditory speech information within the phonological loop, although nonauditory material such as pictures of objects seem to be remembered in terms of their visual rather than sound-based characteristics. A rudimentary form of rehearsal, possibly akin to an immediate echo of the phonological form, appears to be used. Full strategic rehearsal for all linguistically codable material emerges some years later, at around seven years of age."

"Vocabulary size is strongly associated with a range of abilities including general intelligence, reading ability, reading comprehension, and school success (e.g., Anderson & Freebody, 1981; Thomdyke, 1973)."

"Children who experience specific difficulties in learning to read during the early school years but do not have the extreme and generalised language impairments of the children described in the previous section also tend to have poor vocabulary knowledge.
Poor readers also perform badly on verbal short-term memory measures, and their memory deficits have been suggested to be located within the phonological component of working memory (e.g. Jorm, 1983)."

"There are five separate levels of representation involved in translating the conceptual content of the message to the precise articulatory instructions used to produce the desired speech signal. Selection of message to be encoded in linguistic form -> MESSAGE LEVEL (conceptual, nonlinguistic). Lexical units selected corresponding to meaning elements in message-level representation. Functional roles of lexical units specified -> FUNCTIONAL LEVEL. Syntactic frame is selected Phonologically specified lexical units are inserted into frame -> POSITIONAL LEVEL. Phonetic detail of lexical units and grammatical morphemes is specified -> SOUND LEVEL -> ARTICULATORY INSTRUCTIONS"

"The study of how children become skilled readers, and of why some children experience unexpected difficulties in learning to read and spell, has occupied psychologists and educationalists since the end of the last century."

"More frequently, researchers define dyslexia as the failure to acquire literacy at a normal rate in the absence of any obvious factors, such as emotional disorder, serious socioeconomic disadvantage or low intelligence (e.g. Rutter & Yule, 1975; Vellutino, 1979). Researchers using such definitions of dyslexia have estimated its incidence in the general population at around 5% (Lundberg, 1988)."

"A word is recognised by a second strategy, that of phonological recoding, when the reader uses knowledge about the correspondences between letters and sounds to generate a full or partial phonological specification that matches the phonology of a familiar word. The third strategy involves use of context. A word can be “guessed” on the basis of a variety of sources of information—from the picture accompanying it in the book, from the sentence in which it is embedded, and from the child’s expectations. Such contextual factors will in fact influence the generation of a word in combination with a child’s attempt at reading, with the influence ranging from the speeding of fluent reading at one extreme to a complete guess at the other."

"The study of the psychological mechanisms involved on recognising individual words is beset with both empirical inconsistencies and theor etical debate. Many years of intensive research on word recognition have established that the psychological processes involved are exception ally complex. In particular, it has become clear that the way in which people read words can change dramatically according to the task being required of them, and also as a function of the kind of written material involved. Even more importantly for the present concerns, the involvement of phonological working memory in single-word reading appears to depend critically on the nature of the reading task."

"Working memory involvement in word recognition has been the subject of systematic study in three reading populations—skilled adult readers, neuropsychological patients, and children. The principal findings in each of these areas of research are reviewed in this chapter. Before considering this evidence, though, we provide a brief overview of current thinking about the psychological processes involved in reading single words. In particular, we focus on the contentious issue of how, and under what conditions, phonological recoding occurs during reading."

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