工作记忆中“组块”概念的演化及理论模型

在Miller提出“神奇的数字7±2”之后, “块”被很多理论作为个体工作记忆加工过程中具有稳定结构并可用于衡量记忆容量的单位。但随着研究者对“组块”研究的深入, 他们对组块的定义也在发生着改变。与此同时, 不少研究发现个体的年龄阶段与其主要采用的组块层级相对应, 但尚不清楚组块层级的转换是否存在固定的年龄区间, 且对组块机制的解释仍存在分歧。因此本文针对组块定义的发展与演变、年龄阶段特征及其机制三方面展开综合讨论。未来的研究可以更多探讨长时记忆在工作记忆组块运行机制中的作用, 完善不同年龄阶段个体的组块特征, 以及怎样发挥复述策略和“少即是多”原则在组块过程中的优势等问题。     

Seven-month-old infants chunk items in memory

Although working memory has a highly constrained capacity limit of three or four items, both adults and toddlers can increase the total amount of stored information by "chunking" object representations in memory. To examine the developmental origins of chunking, we used a violation-of-expectation procedure to ask whether 7-month-old infants, whose working memory capacity is still maturing, also can chunk items in memory. In Experiment 1, we found that in the absence of chunking cues, infants failed to remember three identical hidden objects. In Experiments 2 and 3, we found that infants successfully remembered three hidden objects when provided with overlapping spatial and featural chunking cues. In Experiment 4, we found that infants did not chunk when provided with either spatial or featural chunking cues alone. Finally, in Experiment 5, we found that infants also failed to chunk when spatial and featural cues specified different chunks (i.e., were pitted against each other). Taken together, these results suggest that chunking is available before working memory capacity has matured but still may undergo important development over the first year of life.     

Infants hierarchically organize memory representations

Throughout development, working memory is subject to capacity limits that severely constrain short‐term storage. However, adults can massively expand the total amount of remembered information by grouping items into chunks. Although infants also have been shown to chunk objects in memory, little is known regarding the limits of this ability. In particular, it remains unknown whether infants can create more complex memory hierarchies, binding representations of chunks into still larger chunks in recursive fashion. Here we tested the limits of early chunking, first measuring the number of items infants can bind into a single chunk and the number of chunks infants can maintain concurrently, and then, critically, whether infants can embed chunked representations into larger units. We tested 14‐month‐old infants' memory for hidden objects using a manual search task in which we manipulated memory load (the number of objects infants saw hidden) and the chunking cues provided. We found that infants are limited in the number of items they can chunk and in the number of chunks they can remember. However, we also found that infants can bind representations of chunks into ‘superchunks’. These results suggest that hierarchically organizing information strongly affects working memory, starting in infancy.     

Why computational models are better than verbal theories: the case of nonword repetition

Tests of nonword repetition (NWR) have often been used to examine children's phonological knowledge and word learning abilities. However, theories of NWR primarily explain performance either in terms of phonological working memory or long‐term knowledge, with little consideration of how these processes interact. One theoretical account that focuses specifically on the interaction between short‐term and long‐term memory is the chunking hypothesis. Chunking occurs because of repeated exposure to meaningful stimulus items, resulting in the items becoming grouped (or chunked); once chunked, the items can be represented in short‐term memory using one chunk rather than one chunk per item. We tested several predictions of the chunking hypothesis by presenting 5–6‐year‐old children with three tests of NWR that were either high, medium, or low in wordlikeness. The results did not show strong support for the chunking hypothesis, suggesting that chunking fails to fully explain children's NWR behavior. However, simulations using a computational implementation of chunking (namely CLASSIC, or Chunking Lexical And Sub‐lexical Sequences In Children) show that, when the linguistic input to 5–6‐year‐old children is estimated in a reasonable way, the children's data are matched across all three NWR tests. These results have three implications for the field: (a) a chunking account can explain key NWR phenomena in 5–6‐year‐old children; (b) tests of chunking accounts require a detailed specification both of the chunking mechanism itself and of the input on which the chunking mechanism operates; and (c) verbal theories emphasizing the role of long‐term knowledge (such as chunking) are not precise enough to make detailed predictions about experimental data, but computational implementations of the theories can bridge the gap.     

Memory span and short-term memory capacity: A developmental study

A memory span task involving series conditions comprised of several different types of material was administered to children from three grade levels (7–12 years of age). As expected, age differences were strongly affected by type of material, with two conditions (consonant letters, words) intended to restrict opportunities for chunking yielding age differences that were negligible, and one condition (consonant-vowel letters) constructed to maximize sequential probability yielding age differences that were large. This finding renders less plausible the popular notion that capacity increases with age, and suggests that age differences in memory span reflect chunking processes. Additional findings, which indicate that age differences in memory span are affected by method of presentation and stage of practice, suggest that these variables should be considered in studies aimed at estimating children's memory capacity.     

Chunking in recall of symbolic drawings

Three experiments explored memory for symbolic circuit drawings using skilled electronics technicians and novice subjects. In the first experiment a skilled technician reconstructed circuit diagrams from memory. Recall showed marked “chunking”, or grouping, by functional units similar to Chess Masters’ recall of chess positions. In the second experiment skilled technicians were able to recall more than were novice subjects following a brief exposure of the drawings. This advantage did not hold for randomly arranged symbols. In the third experiment the size of chunks retrieved systematically increased with additional study time. Supplementary analyses suggested that the chunking by skilled subjects was not an artifact of spatial proximity and chunk statistics, and that severe constraints are placed on any explanation of the data based on guessing. It is proposed that skilled subjects identify the conceptual category for an entire drawing, and retrieve elements using a generate-and-test process.     

Working memory in multilingual children: Is there a bilingual effect?

This research investigates whether early childhood bilingualism affects working memory performance in 6- to 8-year-olds, followed over a longitudinal period of 3 years. The study tests the hypothesis that bilinguals might exhibit more efficient working memory abilities than monolinguals, potentially via the opportunity a bilingual environment provides to train cognitive control by combating interference and intrusions from the non-target language. A total of 44 bilingual and monolingual children, matched on age, sex, and socioeconomic status, completed assessments of working memory (simple span and complex span tasks), fluid intelligence, and language (vocabulary and syntax). The data showed that the monolinguals performed significantly better on the language measures across the years, whereas no language group effect emerged on the working memory and fluid intelligence tasks after verbal abilities were considered. The study suggests that the need to manage several language systems in the bilingual mind has an impact on children's language skills while having little effects on the development of working memory.     

Capacity increase and chunking in the development of short-term memory

The possibility of an age-related increase in the capacity of the short-term store was examined in two short-term memory experiments, and an M-operator model was proposed to account for the data. In the first experiment, lists of 8, 10, and 12 consonants were presented to 10-, 12-, and 14-year-olds. Despite the fact that the amount of chunking was monitored and kept constant across ages, there was a definite developmental increase in short-term memory performance. The size of the increase corresponded to the prediction of Pascual-Leone's M-operator theory. An M-operator model was proposed to account for the relation between performance level and list length at each age, as well as the developmental increase. Predictions of adult performance were tested in a second experiment. Together the two experiments show that an important part of short-term memory development can be explained as a growth in short-term store capacity.     

Working memory in multilingual children: is there a bilingual effect?

This research investigates whether early childhood bilingualism affects working memory performance in 6- to 8-year-olds, followed over a longitudinal period of 3 years. The study tests the hypothesis that bilinguals might exhibit more efficient working memory abilities than monolinguals, potentially via the opportunity a bilingual environment provides to train cognitive control by combating interference and intrusions from the non-target language. A total of 44 bilingual and monolingual children, matched on age, sex, and socioeconomic status, completed assessments of working memory (simple span and complex span tasks), fluid intelligence, and language (vocabulary and syntax). The data showed that the monolinguals performed significantly better on the language measures across the years, whereas no language group effect emerged on the working memory and fluid intelligence tasks after verbal abilities were considered. The study suggests that the need to manage several language systems in the bilingual mind has an impact on children's language skills while having little effects on the development of working memory.     

The Role of Language in Temporal Cognition in 6- to 10-Year-Old Children

The ability to recognize temporal patterns and position events in time emerges during the preschool years and is refined in middle childhood. This study explored individual differences in temporal cognition in relation to verbal and nonverbal abilities. Children (30 boys, 32 girls; M_age = 8;2, age range = 6;0?10;8) completed 3 temporal-cognition tasks measuring estimation of temporal distance (how far events are from the present), knowledge of conventional times of events (specific days or months of events), and flexibility in using the calendar system (arranging nonconsecutive months in order), along with assessments of nonverbal intelligence, verbal short-term memory, visual-spatial working memory, receptive vocabulary, receptive grammar, and reading mastery. Controlling for age, performance across temporal-cognition tasks correlated with language abilities; nonverbal abilities accounted for little to no additional variance. The findings link language skills with the acquisition of conventional time patterns; such patterns developed alongside the ability to gauge distances of events in the past or future and form an organized timeline.     

Recall of random and distorted chess positions: Implications for the theory of expertise

This paper explores the question, important to the theory of expert performance, of the nature and number of chunks that chess experts hold in memory. It examines how memory contents determine players’ abilities to reconstruct (1) positions from games, (2) positions distorted in various ways, and (3) random positions. Comparison of a computer simulation with a human experiment supports the usual estimate that chess Masters store some 50,000 chunks in memory. The observed impairment of recall when positions are modified by mirror image reflection implies that each chunk represents a specific pattern of pieces in a specific location. A good account of the results of the experiments is given by the template theory proposed by Gobet and Simon (in press) as an extension of Chase and Simon’s (1973b) initial chunking proposal, and in agreement with other recent proposals for modification of the chunking theory (Richman, Staszewski, & Simon, 1995) as applied to various recall tasks.     

Visuo-spatial and verbal working memory in the five-disc Tower of London task: An individual differences approach

This paper reports a study of the roles of visuo-spatial and verbal working memory capacities in solving a planning task—the five-disc Tower of London (TOL) task. An individual differences approach was taken. Sixty adult participants were tested on 20 TOL tasks of varying difficulty. Total moves over the 20 TOL tasks was taken as a measure of performance. Participants were also assessed on measures of fluid intelligence (Raven's matrices), verbal short-term storage (Digit span), verbal working memory span (Silly Sentence span), visuo-spatial short-term storage (Visual Pattern span and Corsi Block span), visuo-spatial working memory (Corsi Distance Estimation), visuo-spatial processing speed (Manikin test), and verbal speed (Rehearsal speed). Exploratory factor analysis using an oblique rotation method revealed three factors which were interpreted as (1) a visuo-spatial working memory factor, (2) an age-speed factor, and (3) a verbal working memory factor. The visuo-spatial and verbal factors were only moderately correlated. Performance on the TOL task loaded on the visuo-spatial factor but did not load on the other factors. It is concluded that the predominant goal-selection strategy adopted in solving the TOL relies on visuo-spatial working memory capacity and particularly involves the active “inner scribe” spatial rehearsal mechanism. These correlational analyses confirm and extend results previously obtained by use of dual task methods, (Phillips, Wynn, Gilhooly, Della Sala, & Logie, 1999).     

Individual differences in digit span and chunking

The present experiment examined the relation between digit span and chunking in adults. Chunking was estimated from performance in a serial anticipation task that included run patterns and patterns discovered in conventionally constructed digit-span sequences. Chunking was indexed by the location of errors made on experimenter-defined chunks and by a measure that makes no assumptions about the location of chunk boundaries. Both measures revealed large individual differences in chunking; however, correlations between these differences and span tended to be weak and nonsignificant. Thus, the results provided no evidence that higher digit spans are due to more active chunking processes.     

Differential trajectories of age-related changes in components of executive and memory processes

Several studies have demonstrated age-related declines in general executive function and memory. In this study, we examined cross-sectional and longitudinal age effects in more specific cognitive processes that constitute executive function and memory. We postulated that, whereas some components of executive and memory functions would show age differences and longitudinal declines, other specific abilities would be maintained or even improve with repeated testing. In a sample of individuals ≥55 years old from the Baltimore Longitudinal Study of Aging, we found longitudinal declines in inhibition, manipulation, semantic retrieval, phonological retrieval, switching, and long-term memory over a maximum of 14 years follow-up. In contrast, abstraction, capacity, chunking, discrimination, and short-term memory were maintained or even improved longitudinally, probably due in part to repeated testing. Moreover, whereas several different abilities were correlated across participants' cross-sectional performance, longitudinal changes in performance showed more heterogeneous trajectories. Finally, compared with cross-sectional performance, longitudinal trajectories showed better distinction between participants with and those without later cognitive impairment. These results show that longitudinal cognitive aging of executive and memory functions is not a uniform process but a heterogeneous one and suggest that certain executive and memory functions remain stable despite age-related declines in other component processes. (PsycINFO Database Record (c) 2012 APA, all rights reserved).     

高功能孤独症幼儿空间工作记忆的组块加工缺陷

孤独症谱系障碍者存在空间工作记忆加工缺陷,其具体受损环节尚不明确。组块是一种有效的策略性信息编码方式,是空间工作记忆的关键环节。高度结构化的刺激容易形成高水平组块,因此,刺激结构化程度对记忆效果的影响能够反映个体的组块加工能力。研究采用Sternberg空间工作记忆任务、Corsi空间广度任务,加入刺激结构化因素,考察高功能孤独症幼儿是否存在组块加工缺陷,并探讨组块加工是否直接影响到空间工作记忆容量。实验1采用Sternberg空间工作记忆任务,结果表明,ASD幼儿存在明显的组块加工缺陷。在易于组块的高结构化条件下,健康幼儿的记忆成绩明显较高,而ASD幼儿在高、低结构化条件下的记忆成绩并无显著差异。实验2采用Corsi空间广度任务,结果显示,不论高、低结构化条件,ASD幼儿的空间工作记忆容量均显著低于健康幼儿。但ASD幼儿由于存在组块加工缺陷,在高、低结构化条件下的记忆成绩差异较健康幼儿小。因此,ASD幼儿的组块能力一定程度上影响了空间工作记忆容量。此外,记忆存储器的异常可能也是ASD幼儿空间工作记忆容量不足的重要原因。研究表明,ASD幼儿的空间组块缺陷主要由于弱中央统合的认知风格,他们缺乏自上而下的组块加工动机,难以主动对刺激形成高水平组块编码,从而影响记忆效果。     

Temporal precision and the capacity of auditory–verbal short-term memory

The capacity of serially ordered auditory–verbal short-term memory (AVSTM) is sensitive to the timing of the material to be stored, and both temporal processing and AVSTM capacity are implicated in the development of language. We developed a novel “rehearsal-probe” task to investigate the relationship between temporal precision and the capacity to remember serial order. Participants listened to a sub-span sequence of spoken digits and silently rehearsed the items and their timing during an unfilled retention interval. After an unpredictable delay, a tone prompted report of the item being rehearsed at that moment. An initial experiment showed cyclic distributions of item responses over time, with peaks preserving serial order and broad, overlapping tails. The spread of the response distributions increased with additional memory load and correlated negatively with participants’ auditory digit spans. A second study replicated the negative correlation and demonstrated its specificity to AVSTM by controlling for differences in visuo-spatial STM and nonverbal IQ. The results are consistent with the idea that a common resource underpins both the temporal precision and capacity of AVSTM. The rehearsal-probe task may provide a valuable tool for investigating links between temporal processing and AVSTM capacity in the context of speech and language abilities.     

Statistically Induced Chunking Recall: A Memory-Based Approach to Statistical Learning

The computations involved in statistical learning have long been debated. Here, we build on work suggesting that a basic memory process, chunking, may account for the processing of statistical regularities into larger units. Drawing on methods from the memory literature, we developed a novel paradigm to test statistical learning by leveraging a robust phenomenon observed in serial recall tasks: that short-term memory is fundamentally shaped by long-term distributional learning. In the statistically induced chunking recall (SICR) task, participants are exposed to an artificial language, using a standard statistical learning exposure phase. Afterward, they recall strings of syllables that either follow the statistics of the artificial language or comprise the same syllables presented in a random order. We hypothesized that if individuals had chunked the artificial language into word-like units, then the statistically structured items would be more accurately recalled relative to the random controls. Our results demonstrate that SICR effectively captures learning in both the auditory and visual modalities, with participants displaying significantly improved recall of the statistically structured items, and even recall specific trigram chunks from the input. SICR also exhibits greater test–retest reliability in the auditory modality and sensitivity to individual differences in both modalities than the standard two-alternative forced-choice task. These results thereby provide key empirical support to the chunking account of statistical learning and contribute a valuable new tool to the literature.     

STM capacity for Chinese and English language materials

This paper delineates the theoretical implications of a program of research on short-term memory using Chinese characters as stimuli, and compares the findings with studies of short-term memory that use English language materials. The 14 experiments on which it is principally based, carried out in the People’s Republic of China and in the U.S.A., are reported in detail in Yu et al. (1984), W. Zhanget al. (1984), and G. Zhang and Simon (this issue). One major theoretical product of this research is an experimentally tested model that reconciles the chunking theory of STM capacity with the articulatory loop theory of Baddeley, making good quantitative predictions of capacity compatible with both. Another result, obtained by using homophones as stimuli, is a demonstration that STM is mainly acoustically encoded, but that there are an additional two or three chunks of visually or semantically encoded short-term memory available. Chunks are shown to play the same role in immediate recall and rote learning in both the Chinese language and English language stimuli; and STM capacity, measured in chunks, is essentially the same for materials in both languages.     

Chunking mechanisms in human learning

Pioneering work in the 1940s and 1950s suggested that the concept of 'chunking' might be important in many processes of perception, learning and cognition in humans and animals. We summarize here the major sources of evidence for chunking mechanisms, and consider how such mechanisms have been implemented in computational models of the learning process. We distinguish two forms of chunking: the first deliberate, under strategic control, and goal-oriented; the second automatic, continuous, and linked to perceptual processes. Recent work with discrimination-network computational models of long- and short-term memory (EPAM/CHREST) has produced a diverse range of applications of perceptual chunking. We focus on recent successes in verbal learning, expert memory, language acquisition and learning multiple representations, to illustrate the implementation and use of chunking mechanisms within contemporary models of human learning.     

Singing can facilitate foreign language learning

This study presents the first experimental evidence that singing can facilitate short-term paired-associate phrase learning in an unfamiliar language (Hungarian). Sixty adult participants were randomly assigned to one of three “listen-and-repeat” learning conditions: speaking, rhythmic speaking, or singing. Participants in the singing condition showed superior overall performance on a collection of Hungarian language tests after a 15-min learning period, as compared with participants in the speaking and rhythmic speaking conditions. This superior performance was statistically significant (p < .05) for the two tests that required participants to recall and produce spoken Hungarian phrases. The differences in performance were not explained by potentially influencing factors such as age, gender, mood, phonological working memory ability, or musical ability and training. These results suggest that a “listen-and-sing” learning method can facilitate verbatim memory for spoken foreign language phrases.