Working Memory Underpins Cognitive Development Learning

Why adults may not have memories for experiences that occurred early in childhood.Educ Psychol Rev (2014) 26:197–223 DOI 10.1007/s10648-013-9246-y REVIEW ARTICLE Working Memory Underpins Cognitive Development, Learning, and Education Nelson Cowan Published online: 3 December 2013 # Springer Science+Business Media New York 2013 Abstract Working memory is the retention of a small amount of information in a readily accessible form. It facilitates planning, comprehension, reasoning, and problem solving. I examine the historical roots and conceptual development of the concept and the theoretical and practical implications of current debates about working memory mechanisms. Then, I explore the nature of cognitive developmental improvements in working memory, the role of working memory in learning, and some potential implications of working memory and its development for the education of children and adults. The use of working memory is quite ubiquitous in human thought, but the best way to improve education using what we know about working memory is still controversial. I hope to provide some directions for research and educational practice. Keywords Working memory . Cognitive development . Learning . Education What is Working Memory? An Introduction and Review Working memory is the small amount of information that can be held in mind and used in the execution of cognitive tasks, in contrast with long-term memory, which is the vast amount of information saved in one’s life. Working memory is one of the most widely used terms in psychology. It has often been connected or related to intelligence, information processing, executive function, comprehension, problem solving, and learning in people ranging from infancy to old age, and in all sorts of animals. This concept is so omnipresent in the field that it requires careful examination both historically and in terms of definition to establish its key characteristics and boundaries. By weaving together history, a little philosophy, and empirical work in psychology in this opening section, I hope to paint a clear picture of the concept of working memory. In subsequent sections, implications of working memory for cognitive development, learning, and education will be discussed in turn, though for these broad areas it is only feasible to touch on certain examples. Some researchers emphasize the possibility of training working memory to improve learning and education. In this chapter, I take the complementary view that we must learn N. Cowan (*) Department of Psychological Sciences, University of Missouri, McAlester Hall, Columbia, MO 65211, USA e-mail: cowann@missouri.edu 198 Educ Psychol Rev (2014) 26:197–223 how to adjust the materials to facilitate learning and education with the working memory abilities that the learner has. Organizing knowledge, for example, reduces one’s memory load because the parts do not have to be held in mind independently. Take, for example, the possibility of doing some scouting ahead so that you will know what this article is about, making your task of reading easier. If you tried to read through the headings of this article, you might have trouble remembering them (placing them all in working memory) so as to anticipate how they fit together. If you read Fig. 1, though, it is an attempt to help you organize the information. If it helps you associate the ideas to one another to build a coherent framework, it should help you read by reducing the workingmemory load you experience while reading. In doing so, you are building a rich structure to associate the headings with one another in long-term memory (e.g., Ericsson and Kintsch 1995), which reduces the number of ideas that would have to be held independently in working memory in order to remember the organization. Early History of Working Memory Research John Locke (1690) distinguished between contemplation, or holding an idea in mind, and memory, or the power to revive an idea after it has disappeared from the mind (Logie 1996). The holding in mind is limited to a few concepts at once and reflects what is now called working memory, as opposed to the possibly unlimited store of knowledge from a lifetime that is now called long-term memory. Working memory can be defined as the small amount of information that can be held in an especially accessible state and used in cognitive tasks. Introduction to working memory (What is working memory?) 1800s to 1940s: working memory = use of temporary memory for cognition; relation to brain, consciousness Broad role of working memory in retaining concrete or abstract items and for new concepts, language, problem-solving. Last 64 years: lasting issues. Multi-modularity? Item capacity limits? Loss over time (decay)? Role of working memory in Cognitive Development Role of capacity limits, number of associations that can be formed in idea complexity Role of knowledge, processing speed, and mnemonic strategies Disentangling capacity limits from the other factors Role of working memory in Learning Concept formation: role of associations formed in the focus of attention Role of control processes (staying on task, managing information) Role of mnemonic processing (chunking, rehearsal) Exercise of working memory as a learning vehicle The difference between learning and education: working memory and critical thinking skills Role of working memory in Education Suitability of materials to cognitive level Fig. 1 Schematic diagram of the arguments in the present article Educ Psychol Rev (2014) 26:197–223 199 Philosophers have long been interested in the limits of what can be contemplated, as noted by a leading British economist and logician, William Stanley Jevons. In an article in an article in Science, Jevons (1871) mused (p. 281): ‚It is well known that the mind is unable through the eye to estimate any large number of objects without counting them successively. A small number, for instance three or four, it can certainly comprehend and count by an instantaneous and apparently single act of mental attention.‛ Then he devised a little experiment to test this hypothesis, on himself. On each trial, he casually reached into a jar full of beans, threw several beans onto a table, and tried to estimate their number without counting. After 1,027 trials, he made no errors for sets of three or four beans, with some small errors for sets of five beans, and with increasing magnitudes of error as a function of set size thereafter, up to 15 beans. Despite the problematic nature of the method (in that the bean thrower was also the bean judge), the finding that normal adults typically can keep in mind only about three or four items has been replicated many times in modern research, using methods similar to Jevons (e.g., Mandler and Shebo 1982) and using many other methods (Cowan 2001). The limited amount that could be held in mind at once played an important role in early experimental psychology, e.g., in the early experimental work of Hermann Ebbinghaus (1885/1913) and Wilhelm Wundt (1894/ 1998). On the American front, William James (1890) wrote about a distinction between primary memory, the items in consciousness and the trailing edge of what is perceived in the world, and secondary memory, the items in storage but not currently in consciousness. Recent investigators have considered multiple possible reasons why primary memory might be limited to just a few items at once, including biological accounts based on the need to avoid confusion between concurrent objects in memory, and evolutionary and teleological accounts based on ideas about what capacity might be ideal for learning and memory retrieval (Cowan 2010; Sweller 2011), but as yet the reason is unknown. Ubiquity of the Working Memory Concept When we say that working memory holds a small amount of information, by this term we may be referring to something as abstract as ideas that can be contemplated or something as concrete as objects that can be counted (e.g., beans). The main point of information is that it is the choice of some things out of a greater set of possible things. One of the exciting aspects of working memory is that it may be important on so many different levels and in so many different situations. When you are listening to language, you need to retain information about the beginning of the sentence until you can make sense of it. If you hear Jean would like to visit the third building on the left, you need to recall that the actor in the sentence is Jean. Then, you need to retain the verb until you know what it is she would like to visit, and you need to retain the adjective ‚third‛ until you know, third what; all of the pieces must be put together in the right way. Without sufficient working memory, the information would be lost before you could combine it into a coherent, complete thought. As another example of how working memory is used, when doing simple arithmetic in your head, if you want to add 24 and 18 you may need to find that 4+8=12, retain the 2 while carrying the 1 over to the tens column to make 2+1+1=4 in the tens column, and integrate with the ones columns to arrive at the answer, 42. As a third example, if you are searching for your car in a parking lot, you have to remember the layout of the cars in the region you just searched so that you can avoid wasting time searching the same region again. In the jungle, a predator that turns its vision away from a scene and revisits it moments later may use working memory to detect that something in the scene has shifted; this change detection may indicate the presence of prey. So the information in working memory can range from spoken words and printed digits to cars and future meals. It can even encompass abstract ideas. Consider whether a young child 200 Educ Psychol Rev (2014) 26:197–223 can get a good understanding of what is or is not a tiger (a matter of word category concepts, e.g., Nelson 1974; Saltz et al. 1972). The concept is, in lay terms, a big cat with stripes. It excludes lions, which have no stripes, and it excludes zebras, which are not big cats. The child must be able to keep in mind the notion of a cat and the notion of stripes at the same time in order to grasp the tiger concept correctly. If the child thinks only of the stripes, he or she may incorrectly label a zebra as a tiger. The concept presumably starts out in working memory and, once it is learned, is transferred to long-term memory. At first, an incomplete concept might be stored in long-term memory, leading to misconceptions that are corrected later when discrep­ ancies with further input are noticed and working memory is used to amend the concept in long-term memory. On a more abstract plane, there are more semantic issues mastered somewhat later in childhood (e.g., Clark and Garnica 1974). The concept of bringing something seems to require several conditions: the person doing the bringing must have something at a location other than the speaker’s location (or future planned location), and must accompany that thing to the speaker’s location. You can ask the person to bring a salad to your house, but probably not to take a salad to your house (unless you are not there), and not to send a salad to your house (unless they are not coming along). These conditions can tax working memory. Again, the child’s initial concept transferred from working memory to long­ term memory may be incomplete, and amended later when discrepancies with further input are noticed. Working Memory: The Past 64 Years There are several modern beginnings for the working memory concept. Hebb (1949) had an outlook on temporary memory that was more neurologically based than the earlier concept of primary memory of James (1890). He spoke of ideas as mediated by assemblies of cells firing in a specific pattern for each idea or concept, and only a few cell assemblies would be active, with current neural firing, at any moment. This vision has played an important role in the field. An issue that is raised by this work is whether working memory should be identified with all of the active information that can be used in immediate memory tests, whether conscious or not, or whether it should be reserved to describe only the conscious information, more in the flavor of James. Given that working memory is a term usually used to explain behavioral outcomes rather than subjective reports, it is typically not restricted to conscious primary memory (e.g., see Baddeley 1986; Baddeley and Hitch 1974; Cowan 1988). Cowan explicitly sug­ gested that there are two aspects of working memory storage: (1) the activated portion of long­ term memory, perhaps corresponding to Hebb’s active cell assemblies, and (2) within that activated portion, a smaller subset of items in the focus of attention. The activated memory would consist of a fragmented soup of all kinds of activated features (sensory, phonological, orthographic, spatial, and semantic), whereas the focus of attention would contain just a few well-integrated items or chunks. Contributions of George Miller Miller (1956) discussed the limitation in how many items can be held in immediate memory. In the relevant test procedure, a list of items is seen or heard and immediately afterward (that is, with no imposed retention interval), the list must be repeated verbatim. The ability to do so was said to be limited to about seven chunks, where a chunk is a meaningful unit. For example, the random digit list 582931 may have to be encoded initially as six chunks, one per digit, whereas the sequence 123654 probably can be encoded by most adults as only two chunks (an ascending triplet followed by a descending triplet). Subsequent work has suggested that the number seven is a practical result that emerges on the basis of strategies that participants use and that, Educ Psychol Rev (2014) 26:197–223 201 when it is not possible to use chunking or covert verbal rehearsal to help performance, adults typically can retain only three or four pre-existing chunks (Chen and Cowan 2009; Cowan 2001; Cowan et al. 2012; Luck and Vogel 1997; Rouder et al. 2008). The first mention I have found of the term working memory comes from a book by Miller et al. (1960), Plans and the structure of behavior. The title itself, and the concept of organization, seem reminiscent of the earlier work by Hebb (1949), The organization of behavior. Miller et al. observed that daily functioning in the world requires a hierarchy of plans. For example, your plan to do well at work requires a subplan to be there at time in the morning, which in turn may require subplans to eat breakfast, shower, get dressed, gather work materials, and so on. Each of these plans also may have subplans, and you may have competing plans (such as choosing an after-work activity, calling your mother, or acquiring food for dinner). Our working memory was said to be the mental faculty whereby we remember the plans and subplans. We cannot think about all of them at once but we might, for example, keep in mind that the frying pan is hot while retrieving a knife from the drawer, and we may keep bringing to mind the approximate time so as not to be late. Working memory was said to be the facility that is used to carry out one subplan while keeping in mind the necessary related subplans and the master plan. Contributions of Donald Broadbent In Great Britain, the book by Broadbent (1958) helped to bring the conversation out of the behaviorist era and into an era of cognitive psychology. In a footnote within the book, he sketched a rough information processing diagram that showed information progressing from a sensory type of store that holds a lot of information briefly, through an attention filter to essentially a working memory that holds only a few items, to a long-term memory that is our storehouse of knowledge accumulated through a lifetime. The empirical basis for the model came largely from his work with selective attention, including many dichotic listening studies in which the task was to listen to the message from one ear and ignore the message from the other ear, or report both messages in some order. The motivation for this kind of research came largely from practical issues provoked by World War II, such as how to help a pilot listen to his own air traffic control message while ignoring messages meant for other pilots but presented in the same channel. An important theoretical outcome, however, was the discovery of a difference between a large-capacity but short-lived sensory memory that was formed regardless of attention, and a longer-lived but small-capacity abstract working memory that required attention. Contributions of Alan Baddeley and Graham Hitch Miller et al. (1960) may have devised the term working memory, but they were not the predominant instigator of the work that has occurred subsequently in the field. Google Scholar does show it with over 5,600 citations. A chapter by Baddeley and Hitch (1974), though, is listed with over 7,400 citations and a 1992 Science article summarizing that approach has over 14,500 citations. In the 1974 chapter, the term working memory was used to indicate a system of temporary memory that is multifaceted, unlike the single store such as James’ primary memory, or the corresponding box in the model by Broadbent (1958), or an elaborated version of it as in the model of Atkinson and Shiffrin (1968), none of which would do. In fact, a lot of investigators in the 1960s proposed variations of information processing models that included a single short-term memory store, and Baddeley often has referred to these together, humorously, as the ‚modal model,‛ providing a sketch of it with sensory, short-term, and long-term memory boxes as in the Broadbent and the Atkinson/Shiffrin models. (When the humor and the origin of the phrase ‚modal model‛ are forgotten, yet the phrase is still widely used, it seems sad somehow.) 202 Educ Psychol Rev (2014) 26:197–223 The main point emphasized by Baddeley and Hitch (1974) is that there were diverse effects that appeared to implicate short-term memory, but that did not converge to a single component. Phonological processing interfered most with phonological storage, visual–spatial processing interfered with visual–spatial storage, and a working memory load did not seem to interfere much with superior memory for the end of a list, or recency effect. Conceptual learning did not depend heavily on the type of memory that was susceptible to phonological similarity effects, and a patient with a very low memory span was still able to learn new facts. To account for all of the dissociations, they ended up concluding that there was an attention-related control system and various storage systems. These included a phonological system that also included a covert verbal rehearsal process, and a visual–spatial storage system that might have its own type of nonverbal rehearsal. In the 1974 version of the theory, there were attention limits on the storage of information as well as on processing. In a 1986 book, Baddeley eliminated the attention-dependent storage but in a 2000 paper, a new component was added in the form of an episodic buffer. This buffer might or might not be attention-dependent and is responsible for holding semantic information for the short term, as well as the specific binding or association between phonological and visual–spatial information. Baddeley and Hitch called the assembly or system of storage and processing in service of holding information in an accessible form working memory, the memory one uses in carrying out cognitive tasks of various kinds (i.e., cognitive work). The model by Cowan (1988) Through the years, there were several other proposals that alter the flavor of the working memory proposal. Cowan (1988) was concerned with how we represent what we know and do not know about information processing. The ‚modal models‛ of which Baddeley …