Working Memory jan 31.1992:255.5044.ProQuest Research Library Articles Working Memory ALAN BADDELEY The t working memory refers to a brain with (5) .We arg if the pro re the simulta g me by the of the store,then possible te atio i)the ntral e tive. d to as che nd is ther cog e short-term the vis ial sk all sh cal l 8h tores and ech-b for Subjects whose her with others,enc JESTION OE WHE ER ME D Instead,we proposed by two subsidia slave system D time including digit the ain-dam n the clasi rved per concept had tems (3).It wa h pa ry for th deficit that uch tasks to predict for a ch has cd h: on the ing clear that t e two has b t:s he sys more tractable es are cor haw work directly on problems of practical significance,suchas reading 556 SCIENCE,VOL.255 Reproduced with permission of the copyright owner.Further reproduction prohibited without permission
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Working Memory Baddeley, Alan Science; Jan 31, 1992; 255, 5044; ProQuest Research Library pg. 556
Central Fig.1.A simplified represen- and reasoning skill.They concluded,however,that the two con- Visuospatial sketch pad tation of the Baddeley and cepts,although closely related,were not synonymous;reasoning Hitch working memory mod- el(5), performance was more dependent on previous knowledge than was working memory,which in contrast appeared to be more dependent on sheer speed of processing. Components of Working Memory comprehension or the reasoning tasks used in tests of intelligence. The weakness of this approach lies in the reliance on complex Although concurrent storage and processing may be one aspect of working memory tasks that have a somewhat arbitrary construction working memory,it is almost certainly not the only feature;indeed, and that do not readily lend themselves to a more detailed analysis Baddeley,Barnard,and Schneider and Detweiler (14)all suggest of the component processes.The dual-task and neuropsychological that the coordination of resources is the prime function of working approach can be utilized to successfully analyze the constituent memory,with memory storage being only one of many potential processes of the slave systems but has made less headway in teasing demands that are likely to be made on the system. apart the complexities of the executive controller. One proposed role for the central executive is that of coordinating information from two or more slave systems.This feature of the central executive was used in an attempt to test the proposal that Individual Differences in Working Memory Alzheimer's disease is associated with a particularly marked deficit in central executive functioning(15).Patients with Alzheimer's disease, The essence of the psychometric approach is to develop tasks that and both young and elderly normal subjects,were required to require the combined storage and manipulation of information and perform two tasks concurrently,one visual and one verbal.The to correlate performance on these tasks with the performance of difficulty of each task was adjusted so that the Alzheimer patients practically and theoretically important cognitive skills.One influen- were making the same proportion of errors as the control subjects, tial study in this area was carried out by Daneman and Carpenter and subjects were then required to perform both tasks at the same (7),who examined the processes involved in reading comprehen- time.Normal elderly subjects were no more impaired than young sion.They devised a series of working memory tasks,one of which controls by this requirement to coordinate,whereas the Alzheimer required subjects to read aloud or listen to a series of short sentences patients showed a marked impairment in performance on both the while retaining the last word from cach sentence for subscquent memory and tracking tasks when required to combine them (16).As immediate recall.Hence,subjects might read or hear:"The sailor the disease progressed,performance on the individual tracking and sold the parrot.The vicar opened the book."They should then memory span tasks held up very well(Fig.2),whereas performance respond "parrot,book."The test typically starts with two sentences on the combined tasks deteriorated markedly,as would be predicted and increases to a point at which subjects are no longer able to recall by the hypothesis of a central executive deficit in Alzheimer's disease all the terminal words.This point is designated the subject's working (17). memory span Daneman and Carpenter,and others using similar techniqucs typically found a correlation coefficient of about 0.5 or 0.6 between The Slave Systems of Working Memory working memory span and reading comprehension,as measured by standardized tests (8).The span task does not have to involve Although an analytic approach to the central executive is begin- language processing because similar correlations are found when ning to bear fruit,there is no doubt that considerably more progress simple arithmetic,combined with word recall,is substituted for has been made with the simpler task of understanding the peripheral sentence processing (9). slave systems of working memory.The dual-task paradigm has been Subsequent studies have indicated that students with high work- used to demonstrate the separability of the memory systems respon- ing memory span were better at coping with "garden path sentenc- sible for learning by means of visuospatial imagery and of learning es,"which contain misleading context,and that they are better at by rote repetition.Imagery is disrupted by the requirement of drawing inferences from text,suggesting that they have a better performing a visuospatial task,such as tracking a spot of light grasp of its meaning (10). moving on a screen,by certain types of eye movement,or by the A sccond arca in which the individual differences approach has presentation of irrelevant visual material during learning(18). been applied to the analysis of working memory is concerned with There are separable spatial and visual components,with different the study of reasoning and concentrates particularly on tasks that have traditionally been used to measure intelligence.One example of this is the working memory analysis by Carpenter,Just,and Shell 70T A 701 (11)of performance on the Raven's matrices task,a test in which one 3 60 60 sector is missing from a complex pattern and the subject is required 50 to choose which of six possible options offers the best completion. 每50 0 Christal (12)has also shown that working memory tests provide 40 吃 improved prediction of technical learning capacity in U.S.Air Force 20 recruits,when compared with more scholastic measures. 0 Kyllonen and Christal (13)have carried out a series of studies, 0 each involving several hundred subjects who were required to MS MS 知 perform a number of standardized tests of reasoning of the type used to assess intelligence as well as a range of tasks that had been devised Flg.2.Dual-task performance of patients with Alzheimer's disease in a series to estimate working memory capacity.For cach study,their results of three sequential tests (1,2,and 3)6 months apart.T,tracking task;MS, memory span task.Normal subjects did not show a difference between single suggested a very high correlation between working memory capacity and dual-task conditions.Data from Baddeley et al.(17). 31 JANUARY 1992 ARTICLES 557 Reproduced with permission of the copyright owner.Further reproduction prohibited without permission
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission
tasks differentially recruiting the two.Farah(19)distinguishes one unfamiliar to the subject being just as disruptive as words in his or imagery component that is principally concerned with the represen- her native tongue and nonsense syllables being as disruptive as tation of pattern information and that involves the occipital lobes meaningful words.The effect is not due to simple distraction, from a second more spatial component that scems to be dependent becausc loud bursts of noise have little or no effect (25).These on parietal lobe functioning.Neuropsychological evidence supports results are interpreted under the assumption that disruptive spoken this dichotomy,with some patients having great difficulty in imag- material gains obligatory access to the phonological memory store. ing and recalling such visual features as the shape of the ears of a 3)The word-length effect.This provides evidence on the nature of spaniel dog or the color of a pumpkin but having no difficulty in the subvocal rehearsal process.Memory span for words is inversely spatial tasks such as describing routes or locating towns on maps; related to spoken duration of the words.Subjects can generally other patients show exactly the reverse pattern of deficits(20). remember about as many words as they can say in 2 seconds(26). Having found ways of scparately disrupting spatial and verbal This phenomenon accounts for differences in digit span when processing,one can explore the relative contribution of different subjects are tested in different languages;languages in which digits subsystems to complex tasks.One example of this application tend to have long vowel sounds or more than one syllable take concerns the nature of the cognitive processes involved in playing longer to rehearse and lead to shorter memory spans (27).The chess.The literature reviewed by Holding [in(21)]indicates that model can also explain the marked tendency for digit span in both visual and verbal coding have been claimed to be crucial by children to increase with age;as children get older,they are able to different studies that principally rely on subjective report.We have rehearse faster (28). sought more objective evidence through a series of experiments that 4)Articulatory suppression.It is possible to disrupt the use of utilize the secondary-task technique to disrupt either the phonolog- subvocal rehearsal by requiring subjects to utter some repeated ical loop,the sketch pad system,or the central executive.Our first irrelevant sound,such as the word "the."This process,known as study involved memory for complex chess positions and tested articulatory suppression prevents the subjects from rehearsing the subjects ranging from the modest club player to the international material they are trying to remember and thus removes the effect of grand master.As expected,expertise correlated highly with memory word length.Suppression also prevents subjects from registering performance,but all subjects showed the same basic pattern:no visually presented material in the phonological store.Recall of such disruption from the concurrent verbal task but clear impairment visual material is reduced,and the acoustic similarity effect is from the tasks occupying the visuospatial sketch pad or the central abolished (29). executive.A second study required subjects to choose the optimum The performance of neuropsychological patients with impaired next move from a complex middle-game position and found exactly short-term memory can also be explained as a deficit in the phono- the same pattern.Disruption of verbal activity had no effect,whereas logical store.They typically show no evidence of phonological visuospatial disruption was clear,and this problem-solving task was coding in memory tasks when presentation is visual,no word length even more susceptible to central executive disruption than the task in effect,and no influence of articulatory suppression,suggesting that the first study (22). these patients make little or no use of their defective phonological short-term store (30). Analyzing the Phonological Loop The Function of the Phonological Loop The phonological loop is probably the simplest and most exten- sively investigated component of working memory.It lies closest to Patients with a specific phonological loop deficit seem to have the earlier concept of short-term memory and has been investigated remarkably few signs of general cognitive impairment.Although most extensively with the memory-span procedure.It is assumed to they typically have difficulty in comprehending certain types of comprise two components,a phonological store that can hold complex sentences,interpretation of results in this area remains acoustic or speech-based information for 1 to 2 scconds,coupled controversial (31).The most commonly held view is that the with an articulatory control process,somewhat analogous to inner phonological store serves as a backup system for comprehension of speech.This system serves two functions;it can maintain material speech under taxing conditions but may be less important with within the phonological store by subvocal repetition,and it can take simple,clearly presented material. visually presented material such as words or nameable pictures and In recent years we have been exploring another possible function of register them in the phonological store by subvocalization. this systcm,namely,its role in long-term phonological learning,such This simple model is able to give a good account of a rich range as acquiring the vocabulary of one's native,or even a forcign, of laboratory-based findings.These include the following: language.In one study,we asked a patient with a very specific 1)The acoustic similarity effect.This is the observation that the short-term phonological memory deficit to learn eight items of immediate ordered recall of items is poorer when they are similar Russian vocabulary,a language with which the patient was unfamiliar; rather than dissimilar in sound (23).Hence,hearing and repeating we compared the results with the patient's capacity to learn to dissimilar words such as "pit,day,cow,pen,rig,"is easier than a associate arbitrary pairs of words in the patient's native language(32). phonologically similar scquence such as"man,cap,can,map,mad." People tend to learn pairs of familiar words in terms of their meaning, This phenomenon is assumed to occur because the basic code and,as expected,the patient's performance on this task was entirely involved in the store is phonological;similar items have fewer normal.In contrast,the patient failed to learn the Russian words with distinguishing cues than dissimilar items and are therefore more auditory presentation and was severely impaired relative to control susceptible to being forgotten.Similarity of meaning does not have subjects even when presentation was visual.This result suggests that this effect,suggesting that this subsystem docs not reflect semantic short-term phonological storage is important for new long-term coding. phonological learning.Subsequent studies with normal adults have 2)The irrelevant speech effect.This refers to a reduction in recall of shown that factors that influence the phonological loop,such as lists of visually presented items brought about by the presence of articulatory suppression,word length,and phonological similarity, irrelevant spoken material(24).Once again,the semantic character- strongly influcnce foreign vocabulary acquisition yet show no effect on istics of the material are not important,with a language that is learning to associate pairs of familiar words(33). 558 SCIENCE,VOL.255 Reproduced with permission of the copyright owner.Further reproduction prohibited without permission
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission
REFERENCES AND NOTES Sec A.D. ating back un n Am Wh 126(1970) ord rep opraion of th phonologic on and .term store Hitch.in The of the phonological crm stor .Verb.B 8leenhegesof4and5yesTmearcas CA. .19.4502 9. rics of 10. s to the childre Toh09649w, bulary and to bea p ce Base d R.E 4389 mulation of new word lea ing(36、we wo gr with low h on of En sh as a s young 16. of nonword repetiti 03(1 related with the earlier mea gain. ry: arly the 1990 edictor Thus,the evide aue.1980.t m pho ory I cru H9 Conclusion V.R The concept of a wo king men system that temp 55.7s ():AD.Badeley.. of the p ach have 25.H. that th con 28. G.L ption.In the A. 29.A.D 86,23198D. which they can b D on and spcech pro The (10 The central exe 181,439(1990) ects a system cered with the attention in then stud of atte n and the 38. This artice as S.Dei 31 JANUARY 199 ARTICLES 556 Reproduced with permission of the copyright owner.Further reproduction prohibited without permission
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission
