Discussion - Cognitive Deficits
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Baddeley, A. D. (1968). How does acoustic similarity influence short-term memory? Quarterly Journal of Experimental Psychology, 20, 249-264.
Baddeley, A. D. (1978). The trouble with levels: A reexamination of Craik and Lockhart's framework for memory research. Psychological Review, 85, 139-152.
Baddeley, A. D. (1992, January 31). Working memory. Science, 255, 556-559.
Baddeiey, A. D. (1996). Exploring the central executive. Quarterly Journal of Experimental Psychology, 49A, 5-28.
Baddeley, A. D. (2000). The episodic buffer: A new component of working memory? Trends in Cognitive Sciences, 4, 417-423.
Baddeley, A. D., & Andrade. J. (2000). Working memory and the vividness of imagery. Journal of Experimental Psychology: General, 129, 126-145.
Baddeley, A. D., Bressi, S., Delia Sala, S., Logie, R., & Spinnler, H. (1991). The decline of working memory in Alzheimer's disease: A longitudinal study. Brain, 114, 2521-2542.
Baddeley, A. D., Emslie, H., Kolodny, J., & Duncan, J. (1998). Random generation and the executive control of working memory. Quarterly Journal of Experimental Psychology, 51A, 818-852.
Baddeley, A. D., Gathercole, S. E., & Papagno, C. (1998). The phonological loop as a language learning device. Psychological Review, 105, 158-173.
Baddeley, A. D., & Hitch, G. (1974). Working memory. In G. A. Bower (Ed.), Recent advances in learning and motivation {Vol. 8, pp. 47-90). New York: Academic Press.
Baddeley, A. D., Papagno, C , & Vallar, G. (1988). When long-term learning depends on short-term storage. Journal of Memory and Language, 27, 586-595.
Baddeley, A. D., Thomson, N., & Buchanan, M. (1975). Word length and the structure of short-term memory. Journal of Verbal Learning and Verbal Behavior, 14, 575-589.
Baddeley, A. D., Vargha-Khadem, F., & Mishkin, M. (2001). Preserved recognition in a case of developmental amnesia: Implications for the acquisition of semantic memory. Journal of Cognitive Neuroscience, 13, 357-369.
Baddeley, A. D., & Warrington, E. K. (1970). Amnesia and the distinction between long- and short-term memory. Journal of Verbal Learning and Verbal Behavior, 9, 176-189.
Baddeley, A. D., & Wilson, B. A. (1994). When implicit learning fails: Amnesia and the problem of error elimination. Neuropsychologia, 32, 53-68.
Brooks, D. N., & Baddeley, A. D. (1976). What can amnesic patients leam? Neuropsychologia, 14, 111-122.
Godden, D., & Baddeley, A. D. (1975). Context-dependent memory in two natural environments: On land and under water. British Journal of Psychology, 66, 325-331.
Salame, P., & Baddeley, A. D. (1982). Disruption of short- term memory by unattended speech: Implications for the structure of working memory. Journal of Verbal Learning and Verbal Behavior, 21, 150-164.
Vallar, G., & Baddeley, A. D. (1984). Fractionation of working memory: Neuropsychological evidence for a phonological short-term store. Journal of Verbal Learning and Verbal Behavior, 23, 151-161.
s Working Memory Still Working? Man I). Baddeley
University of Bristol
• The current state of A. D. Baddeley and G. J. Hitch's (1974) multicomponent working memory model is reviewed. The phonological and visuospatial subsystems have been extensively investigated, leading both to challenges over interpretation of individual phenomena and to more detailed attempts to model the processes underlying the subsystems. Analysis of the controlling
Editor's Note Alan D. Baddeley received the Award for Distinguished Scientific Contributions. Award winners are invited to de- liver an award address at APA '$ annual convention. This award address was delivered at the 109th annual meeting, held August 24-28, 2001, in San Francisco. Articles based on award addresses are not peer reviewed, as they are the expression of the winners' reflections on the occasion of receiving an award.
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central executive has proved more challenging, leading to a proposed clarification in which the executive is assumed to be a limited capacity attentional system, aided by a newly postulated fourth system, the episodic buffer. Current interest focuses most strongly on the link between working memory and long-term memory and on the processes allowing the integration of information from the component subsystems. The model has proved valuable in accounting for data from a wide range of participant groups under a rich array of task conditions. Working memory does still appear to be working.
The term working memory appears to have been first pro- posed by Miller, Galanter, and Pribram (1960) in their classic book Plans and the Structure of Behavior. The term has subsequently been used in computational modeling ap- proaches (Newell & Simon, 1972) and in animal learning studies, in which the participant animals are required to hold information across a number of trials within the same day (Olton, 1979). Finally, within cognitive psychology, the term has been adopted to cover the system or systems involved in the temporary maintenance and manipulation of information. Atkinson and Shiffrin (1968) applied the term to a unitary short-term store, in contrast to the pro- posal of Baddeley and Hitch (1974), who used it to refer to a system comprising multiple components. They empha- sized the functional importance of this system, as opposed to its simple storage capacity. It is this latter concept of a multicomponent working memory that forms the focus of the discussion that follows. I myself have been using the concept for over 25 years; does it still work?
Before addressing this issue, it is perhaps appropriate to consider what are the criteria for working. The multicom- ponent model of working memory was proposed as a theo- retical framework whose function was to give an economi- cal and coherent account of a relatively wide range of data. Its success should be judged in terms of its continuing ca- pacity to do so and to prompt new questions that in turn add to the basic understanding of cognition. To work, therefore, requires breadth of coverage coupled with a ca- pacity to stimulate further research and to incorporate more precise quantitative and/or computational models. So, how well is working memory working?
Baddeley and Hitch (1974) proposed that the earlier uni- tary concept should be elaborated into a three-component system. As Figure 1 shows, this comprises a limited capac-
Figure 1 The Model of Working Memory Proposed by Baddeley and Hitch (1974)
ity attentional controller, the central executive, aided by two subsystems, one concerned with acoustic and verbal information, the articulatory (subsequently phonological) loop, and the other performing a similar function for visual and spatial information, the visuospatial scratchpad (subse- quently sketchpad).1 Much of the earlier work concentrated on these two subsystems, on the grounds that they ap- peared to offer more tractable problems than did the central executive. For that reason, they are discussed first.
The Phonological Loop
This system was proposed to give an account of the sub- stantial evidence that had already accumulated concerning short-term verbal memory, typically involving the classic digit span procedure. The articulatory loop was assumed to comprise two components, a phonological store and an ar- ticulatory rehearsal system. Traces within the store were assumed to decay over a period of about two seconds un- less refreshed by rehearsal, a process akin to subvocaliza- tion and one that is dependent on the second component, the articulatory system (Baddeley & Hitch, 1974).
The store was assumed to be reflected in the phonologi- cal similarity effect, whereby immediate serial recall of items that are similar in sound (e.g., the letters B, V, G, T, C, D) is poorer than that of dissimilar items (e.g., F, K, Y, W, M, R; Conrad & Hull, 1964). Similarity of meaning, however, typically has little effect in the standard immedi- ate serial recall paradigm (Baddeley, 1966b). The reverse is true of the multitrial long-term learning of 10-item se- quences, which appears to depend principally on semantic rather than acoustic coding (Baddeley, 1966a).
The articulatory rehearsal component was proposed to give an account of the word length effect, whereby imme- diate serial recall is a direct function of the length of the items being retained (Baddeley, Thomson, & Buchanan, 1975). Hence, a sequence such as sum, pay, wit, bar, hop is much more likely to be recalled correctly than helicop- ter, university, television, alligator, opportunity. This was originally proposed to reflect the slower rehearsal of longer words, which allows greater forgetting. It has also been claimed to result from forgetting during the process of re- call, which again tends to be slower with longer words (Cowan et al., 1992; Dosher & Ma, 1998). It now appears that both of these processes are important (Baddeley, Chin- cotta, Stafford, & Turk, in press). Consistent with this view is the fact that when rehearsal is prevented by articulatory suppression, the repetition of an irrelevant sound such as the word the, the word length effect disappears (Baddeley et al., 1975).
Visuospatial Sketchpad
Central k Executive^,
Phonological Loop
' Articulatory was changed to phonological to emphasize the fact that this subsystem is not limited to the articulatory component. The term sketchpad was adopted to emphasize that subsystem's visuospatial char- acteristics.
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The process of subvocal articulation also seems to play an important role in registering visually presented material within the phonological loop. Hence, aiticulatory suppres- sion eliminates the effect of phonological similarity when material is presented visually but not with auditory presen- tation, which is assumed to provide direct access to the phonological store (Baddeley, Lewis, & Vallar, 1984; Mur- ray, 1968). Finally, immediate serial verbal memory is im- paired by the presentation of irrelevant auditory material that the participants are instructed to ignore (Colle & Welsh, 1976; Salame & Baddeley, 1982). The disruptive effect is not limited to speech, being also found with fluc- tuating tones, although not when white noise varies in loudness (Jones, 1993). Precise interpretation of the irrele- vant sound effect remains equivocal (Baddeley, 2000b; Jones & Tremblay, 2000; Neath, 2000).
The strength of the phonological loop model resides in the fact that it offers a simple and coherent account of a relatively complex set of data. It has, furthermore, proved readily applicable to neuropsychological deficits, notably including the case of patients who appear to have impaired short-term memory (STM), as reflected in low digit span, coupled with normal long-term memory (LTM; Shallice & Warrington, 1970; Vallar & Baddeley, 1984). Further light has been thrown on the process of subvocal rehearsal by the study of patients with different speech and language deficits. Hence, patients- who have lost the peripheral con- trol of their speech musculature are still able to rehearse (Baddeley & Wilson, 1985), whereas those who have lost the capacity to construct a speech-motor program centrally show no such capacity (Caplan & Waters, 1995). This sug- gests that rehearsal should be regarded as reflecting the central control of speech rather than the overt capacity to articulate. Finally, Baddeley, Gathercole, and Papagno (1998) have argued strongly that the phonological loop has evolved to support the acquisition by children of their na- tive language and that it plays an important role in adult second-language learning.
There have, however, been challenges to virtually every aspect of the phonological loop hypothesis. For example, Neath and Nairne (1995) and Brown and Hulme (1995) have suggested that the word length effect stems from the greater fragility of multicomponent long words to the processes involved in forgetting. I myself regard this view as having difficulty in accounting for the removal of the word length effect with articulatory suppression (Baddeley et al., 1975) and with the absence of a word length effect in patients with STM deficits (Vallar & Baddeley, 1984; Vallar & Papagno, in press) and in young children who are at a stage before they begin rehearsal (see Gathercole, in press, for a review). However, the issue remains open.
The question of whether short-term forgetting represents trace decay or interference, a classic issue of the 1960s,
remains unresolved. The trace decay assumption was adopted on the basis of rather slender evidence, together with its greater simplicity. An interference theory interpre- tation invites a much tighter specification than my col- leagues and I have felt able to achieve. For example, should it follow the classic stimulus-response associationist principles, as Melton (1962) proposed, or should it be closer to the Waugh and Norman (1965) concept of inter- ference resulting from subsequent items displacing earlier traces within a limited capacity system? Indeed, even trace decay could be seen as a form of interference; given that the nervous system appears to be continuously active, a greater delay will involve more subsequent neural activity leading to a greater potential disruption of the memory trace. Testing any of these is likely to demand a more pre- cise specification of the phonological loop than Baddeley and Hitch (1974) were able to offer.
One aspect of this lack of specificity is particularly im- portant, namely, the failure of the model to give any ac- count of how the serial order of the incoming items is maintained. Although simple chaining models are common within the literature (Murdock, 1993; Wickelgren, 1966), chaining is inconsistent with the pattern of errors observed when participants attempt to remember sequences compris- ing alternate similar and dissimilar items (e.g., B, W, T, R, P, X), where errors fall on the similar items rather than on the dissimilar letters following them (Baddeley, 1968; Hen- son, Norris, Page, & Baddeley, 1996). This result has led to a range of computational and mathematical models at- tempting to specify in considerable detail the processes involved in phonological STM. Some fit readily within the phonological loop framework (Burgess & Hitch, 1992, 1999; Henson, 1998; Page & Norris, 1998), whereas other approaches differ in important ways from the phonological loop model (Brown & Hulme, 1995; Nairne, 1990; Neath, 2000). Although it is certainly too soon to draw any firm conclusions, it is clear that the phonological loop model is capable of more detailed computational specification and that this represents an important route for future develop- ment of the model.
Before moving on from the phonological loop, two fur- ther developments should be discussed. The first of these concerns the interaction between the phonological loop and LTM. Baddeley, Gathercole, and Papagno (1998) proposed that an important evolutionary function of the loop is to facilitate the acquisition of language by maintaining the representation of a new word so as to optimize learning. Evidence for this comes from the impairment of foreign language acquisition in patients with a classical STM defi- cit (Baddeley, Papagno, & Vallar, 1988) and also from normal children, for whom the capacity to hear and repeat back an unfamiliar pseudoword (nonword repetition) pre- dicts level of vocabulary development (Gathercole & Bad- deley, 1989). Children with a specific language impairment
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(SLI) are found to be particularly impaired on nonword repetition. Hence, eight-year-olds with normal nonverbal intelligence, coupled with the verbal development of six- year-olds, showed a level of nonword repetition that was equivalent to that of four-year-olds (Gathercole & Badde- ley, 1990). Bishop, North, and Donlan (1996), carrying out a twin study, found nonword repetition to be strongly asso- ciated with SLI and to have very high heritability. The pre- cise mechanism whereby impaired phonological loop ca- pacity results in poor language development is discussed elsewhere (Baddeley, in press; Baddeley, Gathercole, & Papagno, 1998) but remains an area of considerable current theoretical and empirical activity (Gathercole, 1996).
I should finally address one broad issue, namely, that of whether it is necessary to assume a separate phono- logical store rather than propose that the phenomena de- scribed represent the temporary activation of structures within LTM. Such a view is adopted, for example, by Cowan (2001), whose views otherwise do not differ markedly from my own (Baddeley, 2001). I myself re- ject this view for two reasons. First, I reject this view because LTM activation appears to provide an explana- tion without in fact doing so, unless it specifies the way in which the many different features of working memory can be mapped onto mechanisms within the LTM sys- tem. The second reason stems from the detailed analysis of the evidence, particularly that of neuropsychological patients, whose marked phonological STM deficits can occur with apparently normal language and verbal LTM (Vallar & Baddeley, 1984). Both phonological STM and visuospatial STM also appear to be associated with spe- cific brain locations on the basis of evidence from both lesion and functional imaging studies using both positron emission tomography and functional magnetic resonance imaging (fMRI; see Delia Sala & Logie, in press; Smith & Jonides, 1996; and Vallar & Papagno, in press, for reviews). I therefore continue to hold the posi- tion that the phonological loop represents an active sys- tem for temporary storage that has evolved on the grounds of its functional value. Although it draws on processes that initially developed for speech perception and production, it represents a separate system. A recent and careful review of this whole issue is provided by Margaret Wilson (2001).
The Visuospatial Sketchpad
This system is assumed to be capable of temporarily main- taining and manipulating visuospatial information, playing an important role in spatial orientation and in the solution of visuospatial problems. A good overview is provided by Logie (1995), and an account of neuropsychological defi- cits within this system is given by Delia Sala and Logie (in press). The sketchpad is assumed to form an interface between visual and spatial information, accessed either
through the senses or from LTM. As such, it allows a range of channels of visual information to be bound to- gether with similar information of a motor, tactile, or hap- tic nature. A good deal of research over recent years has been concerned with establishing the potential separability of its visual and its spatial components. Although it is dif- ficult to provide tasks that reflect one or other component in a pure form, there is both behavioral and neuropsycho- logical evidence to suggest an association between spatial STM and the Corsi block-tapping task, in which the partic- ipant attempts to copy a sequence of movements made by the experimenter in tapping an array of blocks. The visual component is reflected more strongly in pattern span. This involves showing the participant a matrix in which half of the cells are filled and requiring immediate recall or recog- nition; the size of the matrix is increased to visual span, at which errors begin to occur (Delia Sala, Gray, Baddeley, Allamano, & Wilson, 1999).
The sketchpad can be disrupted by requiring participants to tap repeatedly a specified pattern of keys or locations, a procedure that impairs the use of visuospatial imagery (Baddeley & Lieberman, 1980). Unattended patterns or visual noise may disrupt the visual component of the sys- tem (Logie, 1986; Quinn & McConnell, 1996).
A role for the sketchpad in sentence processing is indi- cated by recent work involving people with Williams syn- drome (Phillips, Jarrold, Baddeley, Grant, & Karmiloff- Smith, 2001), a genetically based learning disability characterized by relatively preserved language and verbal STM, together with impaired spatial processing and Corsi tapping span (Bellugi, Wang, & Jernigan, 1994; Jarrold, Baddeley, & Hewes, 1999). As Figure 2 indicates, this verbal-spatial dissociation extends to sentence verification; people with Williams syndrome show a specific deficit in processing sentences involving spatial syntactic forms, such as above and below or inside and outside (Figure 2A), as compared with nonspatial forms such as negatives and re- versible passives. The aberrant point (1) on Figure 2B in- volves the lighter-darker distinction that was assumed to be visual but nonspatial.
A challenging issue within this area concerns the nature of visuospatial rehearsal. Logie (1995) regarded the spatial component of the system, which he termed the inner scribe, as the basic mechanism for rehearsal. My own ten- tatively held current view is that a process analogous to attention is capable of maintaining activity through the op- eration of the central executive. I now regard this as a more typical mechanism for maintenance rehearsal than the sub vocal rehearsal component of the phonological loop. I regard this as a special case that stems from human verbal capacity to reproduce incoming verbal material accurately and, with familiar forms such as digits and words, to cor- rect errors on the basis of prior knowledge.
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Figure 2 Processing of Spatial and Nonspatial Syntactic Forms by Groups With Williams Syndrome (WS) and Minimal Learning Disability (MLD) and by Typically Developing (TD) Children
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1 2 3 4 5 6 7 Spatial Category
— • — WS — • — TD —A— MLD
1 2 3 4 5 6 7 8 Nonspatial Category
Note. Williams syndrome is associated with impaired spatial working memory. As Figure 2A shows, it is also associated with difficulty in processing spatially based syntax, as compared with typically developing normal children or with people with minimal learning disability. The difference is not present for nonspa- tial syntactic forms (Figure 2B). Data are from "Spatial Language Difficulties in Williams Syndrome: Evidence for Use of Mental Models?" by C. Phillips, C. Jarrold, A. D. Baddeley, J. Grant, and A. Karmiloff-Smith, 2 0 0 1 , manuscript submitted for publication.
Both neuropsychological evidence and functional imag- ing evidence support the view of the sketchpad as a multi- component system, with occipital lobe activation presum- ably reflecting the visual pattern component, parietal regions representing spatial aspects, and frontal activation
responsible for coordination and control (Smith & Jonides, 1996). Separating the subcomponents of the sketchpad has proved more difficult than dissecting the phonological loop (Delia Sala & Logie, in press). However, one feature sug- gests that future developments may be more rapid. Single- unit recording studies in awake monkeys have allowed the tracing of an active short-term visual memory system that would appear to have considerable similarity to the visuo- spatial sketchpad and its control processes in humans (Goldman-Rakic, 1996). At the same time, the study of visual attentional processes would appear to provide an extremely promising bridge between work on monkeys and work on the visuospatial sketchpad (Humphreys, Duncan, & Treisman, 1998).
The Central Executive
The third component of the working memory framework, the central executive, was initially conceived in the vaguest possible terms as a limited capacity pool of general pro- cessing resources. For the first decade, it served principally as a convenient ragbag into which could be thrust such awkward questions as what determined when the sketchpad or phonological loop was used and how they were com- bined. Implicitly, the central executive functioned as a ho- munculus, a little man who took the important decisions as to how the two slave systems should be used. Although this might seem to be a somewhat cowardly approach to theory, it is to some extent inevitable. All theories delimit their range either implicitly or explicitly. If this were not the case, then interpretation of every experiment, whatever its function, would also require the theorist to give an ac- count of the way in which the instructions had been under- stood, the strategy selected, and, indeed, what motivated the participants. A good experimenter will, of course, be fully aware of these as important variables but very reason- ably not expect to incorporate them explicitly in his or her explanation.
However, the central executive does play a crucial role in the working memory framework and, as such, demands explanation if not immediately, then as part of a more complete theory. The executive may still resemble a ho- munculus, but this is no bad thing as long as it is accepted that the role of a homunculus is to remind researchers of those functions that they have not yet explained (Attneave, 1960). It demands a strategy of systematically attempting to specify these processes and explain them, hopefully in due course leaving nothing further to explain, hence allow- ing the homunculus to retire. My colleagues and I adopted this strategy, concentrating on the attentional control char- acteristics of the central executive and borrowing what was virtually the only model attempting to explain the atten- tional control of action at that time, namely, the supervi- sory attentional subsystem (SAS) model of Norman and Shallice (1986).
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The SAS model was developed to account for two broad types of data, absentmindedness in normal partici- pants (Reason, 1984) and the disturbance of attentional control that frequently accompanies damage to the frontal lobes of the brain (Shallice, 1982). Human action is as- sumed to be controlled principally by an extensive series of schemata and habits that are able to use environmental cues to allow the performance of routine tasks such as driving a car through a busy city to a familiar location. Although this frequently leads to conflicts between differ- ent cues, for example, that of continuing driving to the in- tended goal versus stopping at a red traffic light, it is as- sumed that a number of relatively automatic conflict- resolution processes exist, of the type typically specified in production system models (Newell & Simon, 1972). The SAS is necessary when a new problem occurs, for exam- ple, when driving to an unfamiliar location or dealing with a flat tire. The attentionally limited SAS is capable of com- bining information from LTM with existing stimuli to plan a novel solution and to ensure that the plan is followed. Slips of action occur when the SAS fails to override a habit, such as driving to one's office when intending to go to the supermarket. Patients with frontal lobe damage show attentional problems such as perseverating on a given act because an impaired SAS has led to action being captured by the immediate environmental stimuli (Shallice, 1982).
Having provisionally accepted this existing interpreta- tion of the executive, my colleagues and I then began to explore its potential subprocesses. The first of these was the capacity to focus attention, given the further assump- tion that anything-that limited attentional capacity would impair performance. In one study (Robbins et al., 1996), my colleagues and I examined the effect of tasks that were intended to disrupt the phonological loop, the visuospatial sketchpad, and the centrai executive on chess, an activity that seemed likely to place heavy demands on the central executive. The performance of novices and experts was compared. Articulatory suppression had no impact on per- formance, suggesting no role for verbal working memory. Participants were, however, disrupted by a concurrent visuospatial task and even more impaired by the task of generating random digits, which is assumed to place a heavy load on the central executive (Baddeley, Emslie, Kolodny, & Duncan, 1998). Performance of both experts and novices differed in overall level but showed the same pattern of sensitivity to visuospatial and central executive disruption, both for remembering a chess position and for choosing the best next move.
One does not find this pattern in all complex tasks, however. Retrieval from LTM, for example, does not ap- pear to depend heavily on the executive. In a series of ex- periments, my colleagues and I imposed a demanding sec- ondary task during the process of learning and/or retrieving lists of words (Baddeley, Lewis, Eldridge, & Thomson,
1984). Although concurrent load had a clear effect on learning, it had little influence on recall accuracy. Craik and colleagues have subsequently replicated this and have revealed the further interesting feature that, despite being itself unaffected, retrieval does disrupt the performance of the secondary task, although the degree of impairment is not sensitive to the level of secondary task demand (Craik, Govoni, Naveh-Benjamin, & Anderson, 1996). In conclu- sion, the capacity to focus available attentional capacity is clearly an important feature of the executive. It is, how- ever, important to acknowledge that not all tasks, or indeed all complex tasks, are heavily dependent on this capacity.
A second attentional process attributed to the central executive is that of dividing attention (Baddeley, 1996). Much of my work in this area has focused on patients with Alzheimer's disease (AD), who, in addition to their marked impairment in episodic LTM, show attentional deficits (Perry & Hodges, 1999). This work of my colleagues and myself stemmed from a suggestion that AD patients may have central executive impairment, resulting in the devel- opment of a task that would appear to depend on the cen- tral executive (Baddeley, Bressi, Delia Sala, Logie, & Spinnler, 1991). Patients were required to combine tasks depending principally on the phonological loop (digit span) and on the visuospatial sketchpad (pursuit tracking). In each case, level of performance on the individual tests per- formed alone was titrated to a point at which accuracy was equivalent for AD patients and for both elderly and young control participants. However, when performed simulta- neously, dual-task performance was dramatically impaired by AD but was not affected by age. When the two tasks were performed alone, however, there was no evidence that increasing level of difficulty differentially affected the AD patients (Logie, Delia Sala, Wynn, & Baddeley, 2000). These and other studies using both AD patients and normal participants appear to argue for a separable executive ca- pacity to divide attention (Baddeley, Baddeley, Bucks, & Wilcock, 2001; Bourke, Duncan, & Nimmo-Smith, 1996; Perry & Hodges, 1999).
A third potential executive capacity is that of switching attention, something that is said to be particularly suscepti- ble to frontal lobe damage (Shallice, 1988). After pioneer- ing work by Jersild (1927) and Spector and Biederman, (1976), the topic was largely neglected until revived by an influential paper by Allport, Styles, and Hsieh (1994), whose work suggested that the capacity to switch attention is by no means necessarily one that depends strongly on executive capacity. Indeed, our own recent work (Bad- deley, Chincotta, & Adlam, in press), although indicating some contribution from the executive, has implicated the phonological loop much more strongly, at least in the task that was selected. This result has had the positive effect of alerting my colleagues and me to the potential importance of the phonological loop in controlling action, a point em-
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phasized by the classic work of Vygotsky (1962) and Luria (1959) and more recently raised by Miyake and Shah (1999). The question of whether task switching should be regarded as an executive process, or perhaps a range of pro- cesses, remains to be decided (see Monsell & Driver, 1999).
The Episodic Buffer
A fourth role suggested for the central executive is that of forming an interface between the subsystems and LTM (Baddeley, 1996). This problem has been largely ignored by the model. It is reflected very clearly in the contrast between immediate memory for prose and for unrelated words, with word span typically being about 5 items, whereas sentence span may be as high as 16 words (Bad- deley, Vallar, & Wilson, 1987). The simple assumption would be to suggest that the other 10 or 11 words come from LTM, in which case a patient with a very specific STM deficit should have a sentence span of around 10. In fact, it is about 5 (Vallar & Baddeley, 1984). It is also the case that immediate memory is sensitive to semantic simi- larity, provided the material is meaningful (Baddeley, in press; Baddeley & Levy, 1971), and that evenspan for un- related words is susceptible to variables such as word fre- quency and imageability, which are presumed to represent LTM rather than the phonological loop (Hulme, Rooden- rys, Brown, & Mercer, 1995).
Also problematic for the model is the recall of prose paragraphs. Although brain-damaged patients typically do poorly on both immediate and delayed recall of prose pas- sages, a few patients appear to show excellent immediate recall despite dense amnesia that reduces delayed recall to zero. Such patients typically have well-preserved intelli- gence and central executive capacity (Baddeley & Wilson, in press). Within the tripartite model, however, it is diffi- cult to provide a convincing account, given the limited ca- pacity of the subsystems and the assumption that the cen- tral executive is a purely attentional system without its own storage capacity (Baddeley, 1996; Baddeley & Logie, 1999). Prose recall typically reflects the process of chunk- ing, whereby recall is enhanced by aggregating items into larger units—words into phrases, for example—hence al- lowing more economical storage (Miller, 1956; Miller & Selfridge, 1950). Despite its generality and importance, the tripartite working memory model provides no adequate explanation of chunking. The capacity of densely amnesic patients to remember complex material is not limited to prose recall. E. Tulving (personal communication, 1999) described a densely amnesic patient who remains an excel- lent bridge player, able not only to remember the contract bid but also to keep track of which cards have been played during a game well enough to win the rubber.
Another problem for the tripartite model is that of how information from the two subsidiary systems could be bound together. Even simple verbal span shows evidence
of combined verbal and visual encoding (Chincotta, Under- wood, Abd Ghani, Papadopoulou, & Wresinksi, 1999; Lo- gie et al., 2000). If the two stores are separate, how and where is the information combined? Is there perhaps, at some level, a common code?
A similar problem is raised by a recent attempt to use the working memory model to address the question of con- scious awareness (Baddeley & Andrade, 2000). Although my colleagues and I had implicitly assumed that the sketchpad was the basis for visual imagery and the phono- logical loop for auditory, an attempt to spell this out made it clear that there was no direct evidence (Baddeley & Lo- gie, 1992). My colleagues and I therefore decided to tackle this question by asking participants to form images and then judge their vividness, at the same time as performing tasks that were assumed to disrupt each of the two subsid- iary systems proposed as components of working memory. When participants were forming an image of a novel visual or auditory array that they had just experienced, there was good support for the role of the two subsystems; articula- tory suppression reduced the rated vividness of auditory images and spatial suppression that of visual. However, when participants were asked to form images from their long-term knowledge, for example, a local market scene or the sound of a telephone conversation, the pattern changed. The subsidiary systems still played a significant role, but LTM factors became much more important, with rated vividness depending on factors such as whether the scene was active or passive and conventional or bizarre. Vivid- ness appeared to depend on the amount of quasi-sensory knowledge available, whether based on LTM or STM (Baddeley & Andrade, 2000). My colleagues and I drew a number of conclusions, including: (a) Participants were able to make judgments of vividness readily and apparently meaningfully, (b) such judgments reflect a combination of working memory and LTM factors, and (c) the current model is incapable of capturing the mode by which such information is combined. My colleagues and I also con- cluded that this process could not simply reflect a look-up in LTM, given that human beings are apparently able to combine images in a novel way to create, for example, an image of a swan shopping or of an ice-hockey-playing ele- phant, combinations that were unlikely to have been en- countered previously.
Finally, the earlier abandonment of the assumption that the executive has storage capacity left the model with no ready explanation of work on individual differences in working memory that has been the most prominent feature in research on the topic in North America. Daneman and Carpenter (1980, 1983), adopting the broad assumption that working memory involves the capacity simultaneously to process and store information, devised a technique they termed working memory span. Participants are required to read and/or verify a sequence of sentences, storing the last
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word of each, which they then must subsequently recall. They showed that performance on this task correlates with reading comprehension, a finding that has been replicated across many subsequent studies (Daneman & Merikle, 1996). Further research has shown sentence span to be as- sociated with performance on tasks ranging from semantic category generation to speed in acquiring programming or electronics skills (see Engle, 1996, for a review). Kyllonen and Christal (1990) have suggested that working memory span is virtually equivalent to a measure of general intelli- gence and that it further has the advantage of being test- able using material that is less influenced by earlier aca- demic experience than the type of reasoning task that is often used in intelligence testing. However, although work- ing memory span has proved to be a valuable tool, there has been surprisingly little attempt to examine its constitu- ent processes.
One exception to this neglect is the work by Engle and his colleagues, who have typically attempted to provide an explanation in terms of a single overall capacity, such as the capacity for inhibition (Conway & Engle, 1994: Engle, 1996). An important feature of Engle's work has been the demonstration that high- and low-span participants appear to use different strategies, casting serious doubt on the wis- dom of regarding working memory span as a continuous measure (Conway & Engle, 1994}. The measure has also been questioned by neuropsychological evidence suggesting that it probably reflects the operation of a number of sub- components rather than a single pool of processing or in- hibitory capacity (Waters & Caplan, 1996). There is, how- ever, no doubt that, whatever its interpretations, working memory span captures an important cognitive capacity. Once again, however, it is unclear how its findings could be related to the multicomponent model of working memory.
The problems I have described for the working memory model all stem from the need to integrate information from the subsidiary systems and from LTM in a way that allows active maintenance and manipulation. To solve this prob- lem, a fourth component was proposed, the episodic buffer (Baddeley, 2000a, 2001, in press). The episodic buffer is assumed to represent a storage system using a multimodal code. It is assumed to be episodic in the sense that it holds integrated episodes or scenes and to be a buffer in provid- ing a limited capacity interface between systems using dif- ferent codes. It fulfills some of the functions implicitly as- signed by Baddeley and Hitch (1974) to the executive. However, the executive is now assumed to be a purely at- tentional system whose role extends beyond memory func- tion (Baddeley & Logie, 1999), whereas the episodic buffer is assumed to be purely mnemonic in character. It is pro- posed that retrieval from the buffer is through conscious awareness, with the buffer serving the binding function that is assumed to be the principal biological advantage of con- sciousness. This allows multiple sources of information to
be considered simultaneously, creating a model of the envi- ronment that may be manipulated to solve problems and plan future behavior (Johnson-Laird, 1983).
How would the episodic buffer concept account for the problematic data described above? Its account of prose re- call is not dissimilar to the concept of long-term working memory proposed by Ericsson and Kintsch (1995). Com- prehending a complex passage is assumed to require the activation of representations in LTM, in a way already as- sumed by the working memory account of the recency ef- fect (Baddeley & Hitch, 1993), together with the integra- tion of such representations into a novel episodic structure, using LTM to facilitate chunking (Miller, 1956). It is as- sumed that this structure is held within the buffer and maintained using attentionally limited executive processes. This normally leads to the registration and consolidation of this novel representation in LTM. In densely amnesic pa- tients, however, such learning does not occur, with the re- sult that once executive processing is directed elsewhere, ihe structure dissolves and is forgotten. The capacity for temporarily maintaining such structures reflects the capac- ity not only of the buffer itself but also of the subsystems and the central executive. Preservation of all three within amnesic patients is rare but does occasionally occur, result- ing in preserved immediate prose recall coupled with little recall after a delay (Baddeley & Wilson, in press). Within normal participants, my colleagues and I have suggested that the capacity of this complex system is reflected in working memory span.
The revised multicomponent model is shown in Figure 3. It differs from the initial model in two important ways.
Figure 3 The Current Model of Working Memory, Revised to Incorporate links With iong-Term Memory (LTM) by Way of Both the Subsystems and the Newly Proposed Episodic Buffer (Baddeley, 2000a)
Visual Semantics
Episodic LTM
Language
Fluid Systems
Crystallized Systems
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First of all, an explicit link is proposed between the two subsidiary systems and verbal and visual LTM. Although the evidence for this comes principally from the verbal domain (Baddeley, Gathercole, & Papagno, 1998), it seems probable that equivalent visuospatial linking processes ex- ist. These presumably result in the gradual accumulation of nonverbal semantic information, such as the typical colors of objects or how certain animals or people move, together with implicit knowledge of the physical and mechanical world. The flow of information is assumed to be bidirec- tional; the subsidiary systems feed the relevant areas of LTM but are themselves assisted by implicit knowledge of language and of the visuospatial world, making wordlike non- words and patterns that resemble real objects easier to recall.
The second major change within the model is, of course, the episodic buffer. This is assumed to be capable of combining information from LTM with that from the slave systems. The lack of arrows within the model di- rectly linking the subsystems and the buffer represents an initial hypothesis that such transformations depend criti- cally on the central executive. My colleagues and I propose to test this, and in due course, arrows may appear.
Addition of a fourth component after 25 years clearly raises a number of issues. How does the model now differ from others in the literature? Is it neuropsychologically plausi- ble? Most important of all, how might it be tested? Space forbids a detailed discussion of these points (see Baddeley, 2000a), but possible answers to the questions are as follows.
The model differs from Tulving's concept of episodic memory in postulating a structure concerned with tempo- rary storage, albeit one that is intimately connected to epi- sodic LTM. It also differs from Ericsson and Kintsch's (1995) long-term working memory in postulating a separate short-term system over and above that of activated LTM and in tying this system explicitly to the earlier tripartite model. This also represents the principal difference from Cowan's views (Baddeley, 2001; Cowan, 2001).
How might the model be instantiated at a neuropsycho- logical level? First, it seems unlikely that it occupies a sin- gle anatomical location, although the frontal lobes seem likely to play an important role in the coordinating func- tion. Indeed, Prabhakaran, Narayanan, Zhao, and Gabrielli (2000), on the basis of an fMRI study, have explicitly con- cluded that "the present fMRI results provide evidence for another buffer, namely one that allows for temporary reten- tion of integrated information" (p. 89), with the activation responsible being principally frontally located. This is clearly an interesting line to follow.
My colleagues and I are already attempting to explore the concept of an episodic buffer at an experimental level, initially by developing a measure of its capacity. The first attempt involves a measure termed constrained sentence span. The aim is to produce a span measure in which per- formance can be enhanced by combining verbal, semantic,
and visuospatial information. By having sentences of a constant syntactic structure that increase in length while repeatedly using words from a limited set, as in classic span measures, the hope is to minimize any contribution from the passive priming of representations in LTM. The sentences are all of the same subject-verb-object form, with longer sentences being produced by the addition of adjectives and adverbs. Hence, a four-word sentence (ex- cluding function words) would be Peter cleaned the new car, and its eight-word equivalent would be John the angry lawyer instantly borrowed the red book from Lucy.
Initial studies suggest that participants do indeed differ in span measured under these conditions, typically ranging be- tween 5 and 10 words, and that the measure is relatively sta- ble across a number of test trials (Baddeley & Turk, 2001). When participants were required to recall span-length sen- tences or word lists while performing concurrent tasks de- signed to disrupt the phonological loop, the sketchpad, or the executive, constrained sentence span proved most sensitive to concurrent visuospatial and particularly central executive tasks, whereas unrelated word recall was strongly affected by articulatory suppression, suggesting that executive processes are less important in this task. This is, of course, simply the beginning of what is likely to be a long road. My colleagues and I hope, however, that this measure or one of its succes- sors will prove as good an individual difference measure as working memory span, while allowing better control of the material and a more detailed analysis of the underlying pro- cesses. I trust that this will be one of a range of approaches to the analysis of the capacity of working memory to integrate information from many sources and to use this integrated rep- resentation to plan and control future action.
Conclusion
The multicomponent approach to working memory aims to understand the way in which information is temporarily stored and maintained in the performance of complex cog- nitive processing. Although its emphasis on structures rather than processing has not always met with approval, it has for many years formed a productive basis for the sys- tematic accumulation of knowledge about important cogni- tive capacities. Given that I believe this to be one of the most important functions of a theory, I would suggest that working memory has worked and is still working.
Author's Note / am grateful to the British Medical Research Council for their sustained support.
Correspondence concerning this address should be sent to Alan D. Baddeley, Department of Experimental Psychol- ogy, University of Bristol, 8 Woodland Road, Bristol BS8 1TN, United Kingdom. Electronic mail may be sent to alan. baddeley @ bristol. ac. uk.
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References
Allport, A., Styles, E. A., & Hsieh, S. (1994). Shifting attentional set: Exploring the dynamic control of tasks. In C. Umilta & M. Moscovitch (Eds.), Attention and performance XV (pp. 421-452). Cambridge, MA: MIT Press.
Atkinson, R. C , & Shiffrin, R. M. (1968). Human memory: A proposed system and its control processes. In K. W. Spence (Ed.), The psychology of learning and motivation: Advances in research and theory (pp. 89-195). New York: Academic Press.
Attneave, F. (1960). In defence of humunculi. In W. Rosenblith (Ed.), Sensory communication (pp. 777-782). Cambridge, MA: MIT Press.
Baddeley, A. D. (1966a). The influence of acoustic and semantic similarity on long-term memory for word sequences. Quarterly Journal of Experimental Psychology, 18, 302-309.
Baddeley, A. D. (1966b). Short-term memory for word sequences as a function of acoustic, semantic and formal similarity. Quarterly Journal of Experimental Psychology, 18, 362-365.
Baddeley, A. D. (1968). How does acoustic similarity influence short-term memory? Quarterly Journal of Experimental Psychology, 20, 249-264.
Baddeley, A. D. (1996). Exploring the central executive. Quarterly Journal of Experimental Psychology, 49A, 5-28.
Baddeley, A. D. (2000a). The episodic buffer: A new component of working memory? Trends in Cognitive Sciences, 4, 417-423.
Baddeley, A. D. (2000b). The phonological loop and the irrelevant speech effect: Some comments on Neath. Psychonomic Bulletin and Review, 7, 544-549.
Baddeley, A. D. (2001). Comment on Cowan: The magic number and the episodic buffer. Behavioral and Brain Sciences, 24, 117-118.
Baddeley, A. D. (in press). Levels of working memory. In M. Naveh-Benjamin, M. Moscovitch, & H. L. Roediger (Eds.), Perspectives on human memory and cognitive ageing: Essays in honor of Fergus Craik. Hove, England: Psychology Press.
Baddeley, A. D., & Andrade, J. (2000). Working memory and the vividness of imagery. Journal of Experimental Psychology: General, 129, 126-145.
Baddeley, A. D., Baddeley, H., Bucks, R., & Wilcock, G. K. (2001). Attentional control in Alzheimer's disease. Brain, 124, 1492-1508.
Baddeley, A. D., Bressi, S., Delia Sala, S., Logie, R., & Spinnler, H. (1991). The decline of working memory in Alzheimer's disease: A longitudinal study. Brain, 114, 2521-2542.
Baddeley, A. D., Chincotta, D. M., & Adlam, A. (in press). Working memory and the control of action: Evidence from task switching. Journal of Experimental Psychology: General.
Baddeley, A. D., Chincotta, D., Stafford, L , & Turk, D. (in press). Is the word length effect in STM entirely attributable to output delay? Evidence from serial recognition. Quarterly Journal of Experimental Psychology.
Baddeley, A. D., Emslie, H., Kolodny, J., & Duncan, J. (1998). Random generation and the executive control of working memory. Quarterly Journal of Experimental Psychology, 51A, 819-852.
Baddeley, A. D., Gathercole, S. E., & Papagno, C , (1998). The phonological loop as a language learning device, Psychological Review, 105, 158-173.
Baddeley, A. D., & Hitch, G. J. (1974). Working memory. In G. A. Bower (Ed.), Recent advances in learning and motivation (Vol. 8, pp. 47-90). New York: Academic Press.
Baddeley, A. D., & Hitch, G. J. (1993). The recency effect: Implicit learning with explicit retrieval? Memory and Cognition, 21, 146-155.
Baddeley, A. D., & Levy, B. A. (1971). Semantic coding and short-term memory. Journal of Experimental Psychology, 89, 132-136.
Baddeley, A. D., Lewis, V., Eldridge, M., & Thomson, N. (1984). Attention and retrieval from long-term memory. Journal of Experimental Psychology: General, 113, 518-540.
Baddeley, A. D., Lewis, V. I , & Vallar, G. (1984). Exploring the articulatory loop. Quarterly Journal of Experimental Psychology, 36, 233-252.
860 November 2001 • American Psychologist
T hi
s do
cu m
en t i
s co
py ri
gh te
d by
th e
A m
er ic
an P
sy ch
ol og
ic al
A ss
oc ia
tio n
or o
ne o
f i ts
a lli
ed p
ub lis
he rs
. T
hi s
ar tic
le is
in te
nd ed
s ol
el y
fo r t
he p
er so
na l u
se o
f t he
in di
vi du
al u
se r a
nd is
n ot
to b
e di
ss em
in at
ed b
ro ad
ly .
Baddeley, A. D., & Lieberman, K. (1980). Spatial working memory. In R. Nickerson (Ed.), Attention and performance VIII (pp 521-539). Hillsdale, NJ: Erlbaum.
Baddeley, A. D., & Logie, R. H. (1992). Auditory imagery and working memory. In D. Reisberg (Ed.), Auditory imagery (pp. 179-197). Hillsdale, NJ: Erlbaum.
Baddeley, A. D., & Logie, R. H. (1999). Working memory: The multiple-component model. In A. Miyake & P. Shah (Eds.), Models of working memory (pp. 28-61). New York: Cambridge University Press.
Baddeley, A. D., Papagno, C , & Vallar, G. (1988). When long-term learning depends on short-term storage. Journal of Memory and Language, 27, 586-595.
Baddeley, A. D., Thomson, N., & Buchanan, M. (1975). Word length and the structure of short-term memory. Journal of Verbal Learning and Verbal Behavior, 14, 575-589.
Baddeley, A. D., & Turk, D. (2001, June 30). Investigating the episodic buffer. Paper presented at Working Memory meeting, Pralognan, France.
Baddeley, A. D., Vallar, G., & Wilson, B. A. (1987). Sentence comprehension and phonological memory: Some neuropsychological evidence. In M. Coltheart (Ed.), Attention and performance XII: The psychology of reading (pp. 509-529). Hove, England: Erlbaum.
Baddeley, A. D., & Wilson, B. A. (1985). Phonological coding and short-term memory in patients without speech. Journal of Memory and Language, 24, 490-502.
Baddeley, A. D., & Wilson, B. A. (in press). Prose recall and amnesia: Implications for the structure of working memory. Neuropsychologia.
Bellugi, U., Wang, P. P., & Jernigan, T. L. (1994). Williams syndrome: An unusual neuropsychological profile. In S. H. Brodman & J. Grafman (Eds.), Atypical cognitive deficits in developmental disorders: Implications for brain function (pp. 23-56). Hillsdale, NJ: Erlbaum.
Bishop, D. V. M , North, T., & Donlan, C. (1996). Non- word repetition as a behavioural marker for inherited language impairment: Evidence from a twin study. Journal of Child Psychology and Psychiatry, 37, 391-403.
Bourke, P. A., Duncan, J , & Nimmo-Smith, I. (1996). A general factor involved in dual-task performance decrement. Quarterly Journal of Experimental Psychology, 49A, 525-545.
Brown, G. D. A., & Hulme, C. (1995). Modeling item length effects in memory span: No rehearsal needed? Journal of Memory and Language, 34, 594-621.
Burgess, N., & Hitch, G. J. (1992). Towards a network model of the articulatory loop. Journal of Memory and Language, 31, 429-460.
Burgess, N., & Hitch, G. J. (1999). Memory for serial order: A network model of the phonological loop and its timing. Psychological Review, 106, 551-581.
Caplan, D., & Waters, G. S. (1995). On the nature of the phonological output planning processes involved in verbal rehearsal: Evidence from aphasia. Brain and Language, 48, 191-220.
Chincotta, D., Underwood, G., Abd Ghani, K., Papadopoulou, E., & Wresinksi, M. (1999). Memory span for Arabic numerals and digit words: Evidence for a limited-capacity visuo-spatial storage system. Quarterley Journal of Experimental Psychology, 2A, 325-351.
Colle, H. A., & Welsh, A. (1976). Acoustic masking in primary memory. Journal of Verbal Learning and Verbal Behavior, 15, 17-32.
Conrad, R., & Hull, A. J. (1964). Information, acoustic confusion and memory span. British Journal of Psychology, 55, 429-437.
Conway, A. R. A., & Engle, R. W. (1994). Working memory and retrieval: A source-dependent inhibition model. Journal of Experimental Psychology: General, 123, 354-373.
Cowan, N. (2001). The magical number 4 in short-term memory: A reconsideration of mental storage capacity. Behavioral and Brain Sciences, 24, 87-114.
Cowan, N., Day, L., Saults, J. S., Keller, T. A., Johnson, T., & Flores, L. (1992). The role of verbal output time and the effects of word-length on immediate memory. Journal of Memory and Language, 31, 1-17.
Craik, F. I. M., Govoni, R., Naveh-Benjamin, M., & Anderson, N. D. (1996). The effects of divided attention on encoding and retrieval processes in human memory.
November 2001 • American Psychologist 861
T hi
s do
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en t i
s co
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d by
th e
A m
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A ss
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f t he
in di
vi du
al u
se r a
nd is
n ot
to b
e di
ss em
in at
ed b
ro ad
ly .
Journal of Experimental Psychology: General, 125, 159-180.
Daneman, M., & Carpenter, P. A. (1980). Individual differences in working memory and reading. Journal of Verbal Learning and Verbal Behavior, 19, 450-466.
Daneman, M , & Carpenter, P. A. (1983). Individual difference in integrating information between and within sentences. Journal of Experimental Psychology: Learning, Memory, and Cognition, 9, 561-584.
Danemen, M., & Merikle, P. M. (1996). Working memory and language comprehension: A meta-analysis. Psychonomic Bulletin and Review, 3, 422-433.
Delia Sala, S., Gray, C , Baddeley, A. D., Allamano, N., & Wilson, L. (1999). Pattern span: A means of unwelding visuo-spatial memory. Neuropsychologia, 37, 1189-1199.
Delia Sala, S., & Logie, R. H. (in press). Neuropsychological impairments of visuo-spatial STM. In A. D. Baddeley, M. Kopelman, & B. Wilson (Eds.), Handbook of memory disorders (2nd ed.). Chichester, England: Wiley.
Dosher, B. A., & Ma, J. J. (1998). Output loss or rehearsal loop? Output-time versus pronunciation-time limits in immediate recall for forgetting-matched materials. Journal of Experimental Psychology: Learning, Memory, and Cognition, 24, 316-335.
Engle, R. W. (1996). Working memory and retrieval: An inhibition-resource approach. In J. T. E. Richardson, R. W. Engle, L. Hasher, R. H. Logie, E. R. Stoltzfus, & R. T. Zachs (Eds.), Working memory and human cognition (pp. 89-119). New York: Oxford University Press.
Ericsson, K. A., & Kintsch, W. (1995). Long-term working memory. Psychological Review, 102, 211-245.
Gathercole, S. E. (1996). Models of short-term memory. Hove, England: Psychology Press.
Gathercole, S. E. (in press). Memory development during the childhood years. In A. D. Baddeley, M. Kopelman, & B. Wilson (Eds), Handbook of memory disorders (2nd ed.), Chichester, England: Wiley.
Gathercole, S., & Baddeley, A. D. (1989). Development of vocabulary in children and short-term phonological memory. Journal of Memory and Language, 28, 200-213.
Gathercole, S. E., & Baddeley, A. D. (1990). Phonological memory deficits in language disordered children: Is there a causal connection? Journal of Memory and Language, 29, 336-360.
Goldman-Rakic, P. S. (1996). The prefrontal landscape: Implications of functional architecture for understanding human mentation and the central executive. Philosophical Transactions of the Royal Society, Series B, 351, 1445-1453.
Henson, R. N. A. (1998). Short-term memory for serial order: The start-end model. Cognitive Psychology, 36, 73-137.
Henson, R. N. A., Norris, D. G., Page, M. P. A., & Baddeley, A. D. (1996). Unchained memory: Error patterns rule out chaining models of immediate serial recall. Quarterly Journal of Experimental Psychology, 49A, 80-115.
Hulme, C , Roodenrys, S., Brown, G., & Mercer, R. (1995). The role of long-term memory mechanisms in memory span. British Journal of Psychology, 86, 527-536.
Humphreys, G. W., Duncan, J., & Treisman, A. (Eds.). (1998). Brain mechanisms of selective perception and action [Special issue]. Philosophical Transactions of the Royal Society, Series B, 353, 1241-1393.
Jarrold, C , Baddeley, A. D., & Hewes, A. K. (1999). Genetically dissociated components of working memory: Evidence from Downs and Williams syndrome. Neuropsychologia, 37, 637-651.
Jersild, A. T. (1927). Mental set and shift. Archives of Psychology, 89, 5-82.
Johnson-Laird, P. N. (1983). Mental models. Cambridge, England: Cambridge Univerity Press.
Jones, D. (1993). Objects, streams and threads of auditory attention. In A. D. Baddeley & L. Weiskrantz (Eds.), Attention, selection, awareness and control (pp. 87-104). Oxford, England: Oxford University Press.
Jones, D. M., & Tremblay, S. (2000). Interference in memory by process or content? A reply to Neath (2000). Psychonomic Bulletin and Review, 7, 550-558.
Kyllonen, P. C , & Christal, R. E. (1990). Reasoning ability is (little more than) working memory capacity. Intelligence, 14, 389-433.
862 November 2001 • American Psychologist
T hi
s do
cu m
en t i
s co
py ri
gh te
d by
th e
A m
er ic
an P
sy ch
ol og
ic al
A ss
oc ia
tio n
or o
ne o
f i ts
a lli
ed p
ub lis
he rs
. T
hi s
ar tic
le is
in te
nd ed
s ol
el y
fo r t
he p
er so
na l u
se o
f t he
in di
vi du
al u
se r a
nd is
n ot
to b
e di
ss em
in at
ed b
ro ad
ly .
Logie,R. H. (1986). Visuo-spatial processing in working memory. Quarterly Journal of Experimental Psychology, 38A, 229-247.
Logie, R. H. (1995). Visuo-spatial working memory. Hove, England: Erlbaum.
Logie, R. H., Delia Sala, S., Wynn, V., & Baddeley, A. D. (2000, November). Division of attention in Alzheimer's disease. Paper presented at the Psychonomics Society meeting, Los Angeles, CA.
Luria, A. R. (1959). The directive function of speech in development and dissolution: Part I. Word, 15, 341-352.
Melton, A. W. (1962). Implications of short-term memory for a general theory of memory. Journal of Verbal Learning and Verbal Behavior, 2, 1-21.
Miller, G. A. (1956). The magical number seven, plus or minus two: Some limits on our capacity for processing information. Psychological Review, 63, 81-97.
Miller, G. A., Galanter, E., & Pribram, K. H. (1960). Plans and the structure of behavior. New York: Holt, Rinehart & Winston.
Miller, G. A., & Selfridge, J. A. (1950). Verbal context and the recall of meaningful material. American Journal of Psychology, 63, 176-185.
Miyake, A., & Shah, P. (1999). Toward unified theories of working memory: Emerging general consensus, unresolved theoretical issues and future directions. In A. Miyake & P. Shah (Eds.), Models of working memory: Mechanisms of active maintenance and executive control (pp. 28-61). Cambridge, England: Cambridge University Press.
Monsell, S., & Driver, J. (Eds.). (1999). Attention and performance XVIII. Cambridge, MA: MIT Press.
Murdock, B. B., Jr. (1993). TODAM2: A model for the storage and retrieval of item, associative, and serial-order information. Psychological Review, 100, 183-203.
Murray, D. J. (1968). Articulation and acoustic confusability in short-term memory. Journal of Experimental Psychology, 78, 679-684.
Nairne, J. S. (1990). A feature model of immediate memory. Memory and Cognition, 18, 251-269.
Neath, I. (2000). Modelling the effects of irrelevant speech on memory. Psychonomic Bulletin and Review, 7, 403-423.
Neath, I., & Nairne, J. S. (1995). Word-length effects in immediate memory: Overwriting trace-decay theory. Psychonomic Bulletin and Review, 2, 429-441.
Newell, A., & Simon, H. A. (1972). Human problem solving. Englewood Cliffs, NJ: Prentice Hall.
Norman, D. A., & Shallice, T. (1986). Attention to action: Willed and automatic control of behaviour. In R. J. Davidson, G. E. Schwarts, & D. Shapiro (Eds.), Consciousness and self-regulation: Advances in research and theory (Vol. 4, pp. 1-18). New York: Plenum.
Olton, D. S. (1979). Mazes, maps and memory. American Psychologist, 34, 583-596.
Page, M. P. A., & Norris, D. (1998). The primacy model: A new model of immediate serial recall. Psychological Review, 105, 761-781.
Perry, R. J., & Hodges, J. R. (1999). Attention and executive deficits in Alzheimer's disease: A critical review. Brain, 122, 383-404.
Phillips, C , Jarrold, C , Baddeley, A. D., Grant, J., & Karmiloff-Smith, A. (2001). Spatial language difficulties in Williams syndrome: Evidence for use of mental models? Manuscript submitted for publication.
Prabhakaran, V., Narayanan, K., Zhao, Z., & Gabrielli, J. D. E. (2000). Integration of diverse information in working memory in the frontal lobe. Nature Neuroscience, 3, 85-90.
Quinn, G., & McConnell, J. (1996). Irrelevant pictures in visual working memory. Quarterly Journal of Experimental Psychology, 49A, 200-215.
Reason, J. (1984). Absent-mindedness and cognitive control. In J. E. Harris & P. E. Morris (Eds.), Everyday memory, actions and absent-mindedness (pp. 113-132). London: Academic Press.
Robbins, T., Anderson, E., Barker, D., Bradley, A., Fearneyhough, C , Henson, R., Hudson, S., & Baddeley, A. D. (1996). Working memory in chess. Memory and Cognition, 24, 83-93.
Salame, P., & Baddeley, A. D. (1982). Disruption of short- term memory by unattended speech: Implications for the structure of working memory. Journal of Verbal Learning and Verbal Behavior, 21, 150-164.
November 2001 • American Psychologist 863
T hi
s do
cu m
en t i
s co
py ri
gh te
d by
th e
A m
er ic
an P
sy ch
ol og
ic al
A ss
oc ia
tio n
or o
ne o
f i ts
a lli
ed p
ub lis
he rs
. T
hi s
ar tic
le is
in te
nd ed
s ol
el y
fo r t
he p
er so
na l u
se o
f t he
in di
vi du
al u
se r a
nd is
n ot
to b
e di
ss em
in at
ed b
ro ad
ly .
Shallice, T. (1982). Specific impairments of planning. Philosophical Transactions of the Royal Society, London, Series B, 298, 199-209.
Shallice, T. (1988). From neuropsychology to mental structure. Cambridge, England: Cambridge University Press.
Shallice, T.. & Warrington, E. K. (1970). Independent functioning of verbal memory stores: A neuropsychological study. Quarterly Journal of Experimental Psychology, 22, 261-273.
Smith, E. E., & Jonides, J. (1996). Working memory in humans: Neuropsychological evidence. In M. Gazzaniga (Ed.), The cognitive neurosciences (pp. 1009-1020). Canbridge, MA: MIT Press.
Spector, A., & Biederman, 1. (1976). Mental set and mental shift revisited. American Journal of Psychology, 89, 669-679.
Vallar, G.. & Baddeley, A. D. (1984). Fractionation of working memory: Neuropsychological evidence for a phonological short-term store. Journal of Verbal Learning and Verbal Behavior, 23, 151-161.
Vallar, G., & Papagno, C. (in press). Neuropsychological impairments of verbal STM. In A. D. Baddeley, M. Kopelman, & B. Wilson (Eds.) Handbook of memory disorders (2nd ed.) Chichester, England: Wiley.
Vygotsky, L. S. (1962). Thought and language (E. Hanfmann & G. Vakar, Trans.). Cambridge, MA: MIT Press.
Waters, G. S., & Caplan, D. (19%). The capacity theory of sentence comprehension: Critique of Just and Carpenter (1992). Psychological Review, 103, 761-772.
Waugh, N. C , & Norman, D. A. (1965). Primary memory. Psychological Review, 72, 89-104.
Wickelgren, W. A. (1966). Associative intrusions in short- term recall. Journal of Experimental Psychology, 72, 853-858.
Wilson, M. (2001). The case for sensorimotor coding in working memory. Psvchonomic Bulletin and Review, 8, 44-57.
Irving I. Gottesman Award for Distinguished Scientific Contributions
Citation
"For elucidating the genetic and environmental causes of schizophrenia and criminality by combining the perspec- tives of human genetics, epidemiology, and clinical psy- chology. A great synthesizer, Irving I. Gottesman has translated genetic concepts, such as the polygenic/threshold mode! of complex disorders, for broader use in psychology and psychiatry and has created links among scientists in North America, Europe, and Asia. A pioneering researcher, an outstanding mentor, an articulate spokesman for science, and an effective advocate for the mentally ill, he has pro- foundly influenced the field. As a consistently balanced and extraordinarily informed voice in the nalure-nurture debate, he has fostered a more productive public dialogue about !he origins of human behavior."
Biography
Born into a Cleveland, Ohio, working-class family of re- cent Hungarian-Romanian-Jewish immigrants on December 29, 1930, Irving I. Gottesman received his eariy education in a multiethnic, integrated, inner-city elementary school, unaware it was "integrated." He was fortunate thai his par- ents appreciated the value of an excellent public school system that could be afforded by moving into the lowest cost neighborhood within the suburb of Shaker Heights. Virtually all the teachers had master's degrees, and virtu- ally all the high school graduates went on to higher educa-
864 November 2001 • American Psychologist 2001 by ihc AtiBraran PsyrfcctosScBi As.nciaijun. Inc. 00raO6GX/0l/S5.00
Vol. 56. No. I I . 8 M - 8 7 8 [XDI 10 l0.17/»00.]-Ofi6X.56.l 1.864
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