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

Grouping in working memory guides chunk formation in long-term memory: Evidence from the Hebb effect

The Hebb effect refers to the improvement in immediate memory performance on a repeated list compared to unrepeated lists. That is, participants create a long-term memory representation over repetitions, on which they can draw in working memory tests. These long-term memory representations are likely formed by chunk acquisition: The whole list becomes integrated into a single unified representation. Previous research suggests that the formation of such chunks is rather inflexible and only occurs when at least the beginning of the list repeats across trials. However, recent work has shown that repetition learning strongly depends on participants recognizing the repeated information. Hence, successful chunk formation may depend on the recognizability of the repeated part of a list, and not on its position in the list. Across six experiments, we compared these two alternatives. We tested immediate serial recall of eight-letter lists, some of which partially repeated across trials. We used different partial-repetition structures, such as repeating only the first half of a list, or only every second item. We manipulated the salience of the repeating structure by spatially grouping and coloring the lists according to the repetition structure. We found that chunk formation is more flexible than previously assumed: Participants learned contiguous repeated sequences regardless of their position within the list, as long as they were able to recognize the repeated structure. Even when the repeated sequence occurred at varying positions over repetitions, learning was preserved when the repeated sequence was made salient by the spatial grouping. These findings suggest that chunk formation requires recognition of which items constitute a repeating group, and demonstrate a close link between grouping of information in working memory, and chunk formation in long-term memory.

Assessing phonological short-term memory in Greek: Reliability and validity of a non-word repetition test

This study explores the reliability and validity of a NWR task in a large cohort of 387 TD Greek-speaking children aged 7-13 years attending elementary (Grades 2-6) and secondary school (Grade 1), divided into six age groups. Further, the relationship between NWR and reading fluency skills as well as the predictive value of the NWR on reading fluency skills in TD children are examined. To investigate the external reliability of the NWR task, test-retest reliability was performed, and excellent test-retest reliability was found. Internal reliability was explored with Cronbach's alpha coefficient and good reliability was found. To explore convergent validity, correlation analysis between NWR and reading fluency was conducted and significant and strong correlations were found for all age groups excepted 2 (ages 9-10 and 12-13). To examine predictive validity, regression analysis was conducted between these two variables and showed that performance on NWR contributed significantly to reading fluency skills, suggesting that NWR skills are a good predictor of reading skills. Finally, it was explored whether the relevant scores increase as a function of age and found significant differences between groups that differed in 2 years or more, while this difference was no longer significant after 10 years. This finding suggests that phonological STM increases in capacity along with age, but only until the age of 10, where it seems to reach a ceiling. In addition, linear regression analysis showed that age contributed significantly to performance on NWR test. To sum up, the present study provides normative data of a NWR test for a wide age range, which does not exist in the Greek language (particularly for ages over 9 years) and it can be concluded that the present NWR test can be successfully used as a reliable and valid measure of phonological STM in the age range that was examined in this study.

Age-Related Differences of Mandarin Tone and Consonant Aspiration Perception in Babble Noise

PURPOSE

This study investigated the categorical perception of Mandarin tones and consonant aspiration contrasts in babble noise among adults and adolescents aged 12-14 years, and explored the association between working memory and categorical perception.

METHOD

Twenty-four adults and 20 adolescents with Mandarin as their native language were recruited. Their performances of phonemic identification and discrimination in babble noise and quiet conditions, digit span tasks, and nonword repetition were assessed.

RESULTS

Results indicated that, firstly, in the noise condition, both adults and adolescents showed wider boundary widths and lower between-category accuracies when perceiving aspiration of consonants than in the quiet condition, and the categorical boundary of tone perception in adolescents showed a transitional tendency toward Tone 1. Secondly, discrimination of consonant aspiration in adolescents needed to be further developed. Lastly, the accuracy of nonword repetition in adolescents was lower than that in adults, and adults with better auditory verbal working memory had better performance on tone perception.

CONCLUSIONS

Our results provided evidence that tone perception is acquired easier than consonant aspiration perception, and tone perception is more robust and less susceptible to noise interference. Categorical perception performance relates to the capacity and utilization of auditory verbal working memory in some ways.

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.

Chunking and data compression in verbal short-term memory

Short-term verbal memory is improved when words can be chunked into larger units. Miller (1956) suggested that the capacity of verbal short-term memory is determined by the number of chunks that can be stored in memory, rather than by the number of items or the amount of information. But how does the improvement due to chunking come about, and is memory really determined by the number of chunks? One possibility is that chunking is a form of data compression. It allows more information to be stored in the available capacity. An alternative is that chunking operates primarily by redintegration. Chunks exist only in long-term memory, and enable the corresponding items in short-term memory to be reconstructed more reliably from a degraded trace. We review the data favoring each of these views and discuss the implications of treating chunking as data compression. Contrary to Miller, we suggest that memory capacity is primarily determined both by the amount of information that can be stored but also by the underlying representational vocabulary of the memory system. Given the limitations on the representations that can be stored in verbal short-term memory, chunking can sometimes allow the information capacity of short-term memory to be exploited more efficiently. (202 words).

Measuring children's auditory statistical learning via serial recall

Statistical learning (SL) has been a prominent focus of research in developmental and adult populations, guided by the assumption that it is a fundamental component of learning underlying higher-order cognition. In developmental populations, however, there have been recent concerns regarding the degree to which many current tasks reliably measure SL, particularly in younger children. In the current article, we present the results of two studies that measured auditory statistical learning (ASL) of linguistic stimuli in children aged 5-8 years. Children listened to 6 min of continuous syllables comprising four trisyllabic pseudowords. Following the familiarization phase, children completed (a) a two-alternative forced-choice task and (b) a serial recall task in which they repeated either target sequences embedded during familiarization or foils, manipulated for sequence length. Results showed that, although both measures consistently revealed learning at the group level, the recall task better captured learning across the full range of abilities and was more reliable at the individual level. We conclude that, as has also been demonstrated in adults, the method holds promise for future studies of individual differences in ASL of linguistic stimuli.

Does short-term memory develop?

Such is the consistency by which performance on measures of short-term memory (STM) increase with age that developmental increases in STM capacity are largely accepted as fact. However, our analysis of a robust but almost ignored finding - that span for digit sequences (the traditional measure of STM) increases at a far greater rate than span for other verbal material - fundamentally undermines the assumption that increased performance in STM tasks is underpinned by developmental increases in capacity. We show that this digit superiority with age effect is explained by the relatively greater linguistic exposure to random sequences of digits versus other stimuli such as words. A simple associative learning process that learns incrementally from exposure to language accounts for the effect, without any need to invoke an STM mechanism, much less one that increases in capacity with age. By extension, using corpus data directed at 2-3 year old children, 4-6 year old children, and adults, we show that age-related performance increases with other types of verbal material are equally driven by the same basic associative learning process operating on the expanding exposure to language experienced by the child. Our results question the idea that tests such as digit span are measuring a dedicated system for the temporary maintenance and manipulation of verbal material, and as such have implications for our understanding of those aspects of typical and atypical development that are usually accounted for with respect to the operation of such a system.

Does speed of processing or vocabulary size predict later language growth in toddlers?

It is becoming increasingly clear that the way that children acquire cognitive representations depends critically on how their processing system is developing. In particular, recent studies suggest that individual differences in language processing speed play an important role in explaining the speed with which children acquire language. Inconsistencies across studies, however, mean that it is not clear whether this relationship is causal or correlational, whether it is present right across development, or whether it extends beyond word learning to affect other aspects of language learning, like syntax acquisition. To address these issues, the current study used the looking-while-listening paradigm devised by Fernald, Swingley, and Pinto (2001) to test the speed with which a large longitudinal cohort of children (the Language 0-5 Project) processed language at 19, 25, and 31 months of age, and took multiple measures of vocabulary (UK-CDI, Lincoln CDI, CDI-III) and syntax (Lincoln CDI) between 8 and 37 months of age. Processing speed correlated with vocabulary size - though this relationship changed over time, and was observed only when there was variation in how well the items used in the looking-while-listening task were known. Fast processing speed was a positive predictor of subsequent vocabulary growth, but only for children with smaller vocabularies. Faster processing speed did, however, predict faster syntactic growth across the whole sample, even when controlling for concurrent vocabulary. The results indicate a relatively direct relationship between processing speed and syntactic development, but point to a more complex interaction between processing speed, vocabulary size and subsequent vocabulary growth.

Long-term associative learning predicts verbal short-term memory performance

Studies using tests such as digit span and nonword repetition have implicated short-term memory across a range of developmental domains. Such tests ostensibly assess specialized processes for the short-term manipulation and maintenance of information that are often argued to enable long-term learning. However, there is considerable evidence for an influence of long-term linguistic learning on performance in short-term memory tasks that brings into question the role of a specialized short-term memory system separate from long-term knowledge. Using natural language corpora, we show experimentally and computationally that performance on three widely used measures of short-term memory (digit span, nonword repetition, and sentence recall) can be predicted from simple associative learning operating on the linguistic environment to which a typical child may have been exposed. The findings support the broad view that short-term verbal memory performance reflects the application of long-term language knowledge to the experimental setting.

Allen Newell's Program of Research: The Video-Game Test

Newell (1973) argued that progress in psychology was slow because research focused on experiments trying to answer binary questions, such as serial versus parallel processing. In addition, not enough attention was paid to the strategies used by participants, and there was a lack of theories implemented as computer models offering sufficient precision for being tested rigorously. He proposed a three-headed research program: to develop computational models able to carry out the task they aimed to explain; to study one complex task in detail, such as chess; and to build computational models that can account for multiple tasks. This article assesses the extent to which the papers in this issue advance Newell's program. While half of the papers devote much attention to strategies, several papers still average across them, a capital sin according to Newell. The three courses of action he proposed were not popular in these papers: Only two papers used computational models, with no model being both able to carry out the task and to account for human data; there was no systematic analysis of a specific video game; and no paper proposed a computational model accounting for human data in several tasks. It is concluded that, while they use sophisticated methods of analysis and discuss interesting results, overall these papers contribute only little to Newell's program of research. In this respect, they reflect the current state of psychology and cognitive science. This is a shame, as Newell's ideas might help address the current crisis of lack of replication and fraud in psychology.

Sequence Memory Constraints Give Rise to Language-Like Structure through Iterated Learning

Human language is composed of sequences of reusable elements. The origins of the sequential structure of language is a hotly debated topic in evolutionary linguistics. In this paper, we show that sets of sequences with language-like statistical properties can emerge from a process of cultural evolution under pressure from chunk-based memory constraints. We employ a novel experimental task that is non-linguistic and non-communicative in nature, in which participants are trained on and later asked to recall a set of sequences one-by-one. Recalled sequences from one participant become training data for the next participant. In this way, we simulate cultural evolution in the laboratory. Our results show a cumulative increase in structure, and by comparing this structure to data from existing linguistic corpora, we demonstrate a close parallel between the sets of sequences that emerge in our experiment and those seen in natural language.

Developmental Abilities to Form Chunks in Immediate Memory and Its Non-Relationship to Span Development

Both adults and children –by the time they are 2–3 years old– have a general ability to recode information to increase memory efficiency. This paper aims to evaluate the ability of untrained children aged 6–10 years old to deploy such a recoding process in immediate memory. A large sample of 374 children were given a task of immediate serial report based on SIMON®, a classic memory game made of four colored buttons (red, green, yellow, blue) requiring players to reproduce a sequence of colors within which repetitions eventually occur. It was hypothesized that a primitive ability across all ages (since theoretically already available in toddlers) to detect redundancies allows the span to increase whenever information can be recoded on the fly. The chunkable condition prompted the formation of chunks based on the perceived structure of color repetition within to-be-recalled sequences of colors. Our result shows a similar linear improvement of memory span with age for both chunkable and non-chunkable conditions. The amount of information retained in immediate memory systematically increased for the groupable sequences across all age groups, independently of the average age-group span that was measured on sequences that contained fewer repetitions. This result shows that chunking gives young children an equal benefit as older children. We discuss the role of recoding in the expansion of capacity in immediate memory and the potential role of data compression in the formation of chunks in long-term memory.

Questioning short-term memory and its measurement: Why digit span measures long-term associative learning

Traditional accounts of verbal short-term memory explain differences in performance for different types of verbal material by reference to inherent characteristics of the verbal items making up memory sequences. The role of previous experience with sequences of different types is ostensibly controlled for either by deliberate exclusion or by presenting multiple trials constructed from different random permutations. We cast doubt on this general approach in a detailed analysis of the basis for the robust finding that short-term memory for digit sequences is superior to that for other sequences of verbal material. Specifically, we show across four experiments that this advantage is not due to inherent characteristics of digits as verbal items, nor are individual digits within sequences better remembered than other types of individual verbal items. Rather, the advantage for digit sequences stems from the increased frequency, compared to other verbal material, with which digits appear in random sequences in natural language, and furthermore, relatively frequent digit sequences support better short-term serial recall than less frequent ones. We also provide corpus-based computational support for the argument that performance in a short-term memory setting is a function of basic associative learning processes operating on the linguistic experience of the rememberer. The experimental and computational results raise questions not only about the role played by measurement of digit span in cognition generally, but also about the way in which long-term memory processes impact on short-term memory functioning.