Offline consolidation supersedes prior knowledge benefits in children's (but not adults’) word learning

Prior linguistic knowledge is proposed to support the acquisition and consolidation of new words. Adults typically have larger vocabularies to support word learning than children, but the developing brain shows enhanced neural processes that are associated with offline memory consolidation. This study investigated contributions of prior knowledge to initial word acquisition and consolidation at different points in development, by teaching children and adults novel words (e.g., ballow) that varied in the number of English word‐form “neighbours” (e.g., wallow, bellow). Memory for the novel word‐forms was tested immediately after training, the next day and 1 week later, to assess the time‐course of prior knowledge contributions. Children aged 7–9 years (Experiments 1, 3) and adults (Experiment 2) recalled words with neighbours better than words without neighbours when tested immediately after training. However, a period of offline consolidation improved overall recall and reduced the influence of word‐form neighbours on longer term memory. These offline consolidation benefits were larger in children than adults, supporting theories that children have a greater propensity for consolidating phonologically distinctive language information. Local knowledge of just a single word‐form neighbour was enough to enhance learning, and this led to the individual differences in word recall that were related to adults’ global vocabulary ability. The results support the proposal that the relative contributions of different learning mechanisms change across the lifespan, and highlight the importance of testing theoretical models of word learning in the context of development.     

Novel word integration in the mental lexicon: Evidence from unmasked and masked semantic priming

We sought to establish whether novel words can become integrated into existing semantic networks by teaching participants new meaningful words and then using these new words as primes in two semantic priming experiments, in which participants carried out a lexical decision task to familiar words. Importantly, at no point in training did the novel words co-occur with the familiar words that served as targets in the primed lexical decision task, allowing us to evaluate semantic priming in the absence of direct association. We found that familiar words were primed by the newly related novel words, both when the novel word prime was unmasked (Experiment 1) and when it was masked (Experiment 2), suggesting that the new words had been integrated into semantic memory. Furthermore, this integration was strongest after a 1-week delay and was independent of explicit recall of the novel word meanings: Forgetting of meanings did not attenuate priming. We argue that even after brief training, newly learned words become an integrated part of the adult mental lexicon rather than being episodically represented separately from the lexicon.     

注意和记忆对孤独症儿童词汇发展滞后的影响

孤独症语言障碍的表现之一是词汇发展滞后, 可能与其注意和记忆损伤有关。当前研究结果表明, 孤独症儿童在学习词汇时难以利用社会注意提供的有效信息, 且其注意易受到无关刺激干扰, 这可能导致其形成的物体-词汇的联结不稳定, 影响其进一步将这种联结整合到心理词典并保存在记忆中。未来研究应探究联合注意影响孤独症儿童词汇学习的发展轨迹和机制, 儿童的词汇知识对其词汇记忆的影响, 并关注自然场景中孤独症儿童的词汇学习过程和个体差异。     

The acquisition of morphological knowledge investigated through artificial language learning

Affix knowledge plays an important role in visual word recognition, but little is known about how it is acquired. The authors present a new method of investigating the acquisition of affixes in which participants are trained on novel affixes presented in novel word contexts (e.g., sleepnept). Experiment 1 investigated the role of semantic information on affix acquisition by comparing a form-learning condition with a condition in which participants also received definitions for each novel word. Experiment 2 investigated the role of long-term consolidation on affix acquisition by comparing knowledge of learned affixes two days and nearly two months after training. Results demonstrated that episodic knowledge of affixes can be acquired shortly after a single training session using either form or semantic learning, but suggested that the development of lexicalized representations of affixes requires the provision of semantic information during learning as well as a substantial period of offline consolidation.     

Consolidation of vocabulary is associated with sleep in typically developing children,but not in children with dyslexia

Sleep is known to play an active role in consolidating new vocabulary in adults; however, the mechanisms by which sleep promotes vocabulary consolidation in childhood are less well understood. Furthermore, there has been no investigation into whether previously reported differences in sleep architecture might account for variability in vocabulary consolidation in children with dyslexia. Twenty‐three children with dyslexia and 29 age‐matched typically developing peers were exposed to 16 novel spoken words. Typically developing children showed overnight improvements in novel word recall; the size of the improvement correlated positively with slow wave activity, similar to previous findings with adults. Children with dyslexia showed poorer recall of the novel words overall, but nevertheless showed overnight improvements similar to age‐matched peers. However, comparisons with younger children matched on initial levels of novel word recall pointed to reduced consolidation in dyslexics after 1 week. Crucially, there were no significant correlations between overnight consolidation and sleep parameters in the dyslexic group. This suggests a reduced role of sleep in vocabulary consolidation in dyslexia, possibly as a consequence of lower levels of learning prior to sleep, and highlights how models of sleep‐associated memory consolidation can be usefully informed by data from typical and atypical development.     

How does the provision of semantic information influence the lexicalization of new spoken words?

The integration of a novel spoken word with existing lexical items can proceed within 24 hours of learning its phonological form. However, previous studies have reported that lexical integration of new spoken words can be delayed if semantic information is provided during learning. One possibility is that this delay in lexical integration reflects reduced phonological processing during learning as a consequence of the need to learn the semantic associations. In the current study, adult participants learnt novel words via a phoneme monitoring task, in which half of the words were associated with a picture referent, and half were phonological forms only. Critically, participants were instructed to learn the forms of the novel words, with no explicit goal to learn the word–picture mappings. Results revealed significant lexical competition effects emerging one week after consolidation, which were equivalent for the picture-present and form-only conditions. Tests of declarative memory and shadowing showed equivalent performance for picture-present and form-only words, despite participants showing good knowledge of the picture associations immediately after learning. These data support the contention that provided phonological information is recruited sufficiently well during learning, the provision of semantic information does not slow the time-course of lexical integration.     

A probabilistic computational model of cross-situational word learning

Words are the essence of communication: They are the building blocks of any language. Learning the meaning of words is thus one of the most important aspects of language acquisition: Children must first learn words before they can combine them into complex utterances. Many theories have been developed to explain the impressive efficiency of young children in acquiring the vocabulary of their language, as well as the developmental patterns observed in the course of lexical acquisition. A major source of disagreement among the different theories is whether children are equipped with special mechanisms and biases for word learning, or their general cognitive abilities are adequate for the task. We present a novel computational model of early word learning to shed light on the mechanisms that might be at work in this process. The model learns word meanings as probabilistic associations between words and semantic elements, using an incremental and probabilistic learning mechanism, and drawing only on general cognitive abilities. The results presented here demonstrate that much about word meanings can be learned from naturally occurring child-directed utterances (paired with meaning representations), without using any special biases or constraints, and without any explicit developmental changes in the underlying learning mechanism. Furthermore, our model provides explanations for the occasionally contradictory child experimental data, and offers predictions for the behavior of young word learners in novel situations.     

How children block learning from ignorant speakers

Preschool children typically do not learn words from ignorant or unreliable speakers. Here, we examined the mechanism by which these learning failures occur by modifying the comprehension test procedure that measures word learning. Following lexical training by a knowledgeable or ignorant speaker, 48 preschool-aged children were asked either a standard comprehension test question (i.e., “Which one is the blicket”) or a question about the labeling episode (i.e., “Which one did I say is the blicket”). Immediately after training, children chose the object labeled by an ignorant speaker when asked the episode question, but not when asked the semantic question. However, the advantage for episode questions disappeared when the same children were asked after a brief delay. These findings show that children encode their experiences with ignorant speakers, but do not form semantic representations on the basis of those experiences.     

From specific examples to general knowledge in language learning

The extraction of general knowledge from individual episodes is critical if we are to learn new knowledge or abilities. Here we uncover some of the key cognitive mechanisms that characterise this process in the domain of language learning. In five experiments adult participants learned new morphological units embedded in fictitious words created by attaching new affixes (e.g., -afe) to familiar word stems (e.g., “sleepafe is a participant in a study about the effects of sleep”). Participants’ ability to generalise semantic knowledge about the affixes was tested using tasks requiring the comprehension and production of novel words containing a trained affix (e.g., sailafe). We manipulated the delay between training and test (Experiment 1), the number of unique exemplars provided for each affix during training (Experiment 2), and the consistency of the form-to-meaning mapping of the affixes (Experiments 3–5). In a task where speeded online language processing is required (semantic priming), generalisation was achieved only after a memory consolidation opportunity following training, and only if the training included a sufficient number of unique exemplars. Semantic inconsistency disrupted speeded generalisation unless consolidation was allowed to operate on one of the two affix-meanings before introducing inconsistencies. In contrast, in tasks that required slow, deliberate reasoning, generalisation could be achieved largely irrespective of the above constraints. These findings point to two different mechanisms of generalisation that have different cognitive demands and rely on different types of memory representations.     

The role of memory consolidation in generalisation of new linguistic information

Accounts of memory that postulate complementary learning systems (CLS) have become increasingly influential in the field of language learning. These accounts predict that generalisation of newly learnt linguistic information to untrained contexts requires offline memory consolidation. Such generalisation should not be observed immediately after training, as these accounts claim unconsolidated representations are context and hippocampus-dependent and gain contextual and hippocampal independence only after consolidation. We trained participants on new affixes (e.g., -nule) attached to familiar word stems (e.g., buildnule), testing them immediately or 2days later. Participants showed an immediate advantage for trained affixes in a speeded shadowing task as long as these affixes occurred in the stem contexts in which they were learnt (e.g., buildnule). This learning effect generalised to words with untrained stems (e.g., sailnule) only in the delayed test condition. By contrast, a non-speeded definition selection task showed immediate generalisation. We propose that generalisation can be supported by initial context-dependent memories given sufficient processing time, but that context-independent lexical representations emerge only following consolidation, as predicted by CLS accounts.     

Atypicalities in sleep and semantic consolidation in autism

Sleep is known to support the neocortical consolidation of declarative memory, including the acquisition of new language. Autism spectrum disorder (ASD) is often characterized by both sleep and language learning difficulties, but few studies have explored a potential connection between the two. Here, 54 children with and without ASD (matched on age, nonverbal ability and vocabulary) were taught nine rare animal names (e.g., pipa). Memory was assessed via definitions, naming and speeded semantic decision tasks immediately after learning (pre‐sleep), the next day (post‐sleep, with a night of polysomnography between pre‐ and post‐sleep tests) and roughly 1 month later (follow‐up). Both groups showed comparable performance at pre‐test and similar levels of overnight change on all tasks; but at follow‐up children with ASD showed significantly greater forgetting of the unique features of the new animals (e.g., pipa is a flat frog). Children with ASD had significantly lower central non‐rapid eye movement (NREM) sigma power. Associations between spindle properties and overnight changes in speeded semantic decisions differed by group. For the TD group, spindle duration predicted overnight changes in responses to novel animals but not familiar animals, reinforcing a role for sleep in the stabilization of new semantic knowledge. For the ASD group, sigma power and spindle duration were associated with improvements in responses to novel and particularly familiar animals, perhaps reflecting more general sleep‐associated improvements in task performance. Plausibly, microstructural sleep atypicalities in children with ASD and differences in how information is prioritized for consolidation may lead to cumulative consolidation difficulties, compromising the quality of newly formed semantic representations in long‐term memory.     

词汇飞跃: 早期语言发展的里程碑──来自五名汉语儿童的跟踪报告

本文通过对五名汉语儿童的长期跟踪调查,旨在从词汇增长、句法出现和语义发展三方面发掘词汇飞跃时期儿童的语言特征。结果显示：儿童在18个月左右词汇迅猛增长,出现词汇飞跃现象;标志句法出现的词语组合和词汇飞跃在时间上紧密相连;词汇飞跃期儿童语义发展显著,体现为过度延伸词的逐渐减少及下位层次词的逐渐增加。词汇飞跃是汉语儿童早期语言发展的里程碑,表明其在词汇、句法和语义多个语言层面的飞跃。     

The acquisition of morphological knowledge investigated through artificial language learning

Affix knowledge plays an important role in visual word recognition, but little is known about how it is acquired. The authors present a new method of investigating the acquisition of affixes in which participants are trained on novel affixes presented in novel word contexts (e.g., sleepnept). Experiment 1 investigated the role of semantic information on affix acquisition by comparing a form-learning condition with a condition in which participants also received definitions for each novel word. Experiment 2 investigated the role of long-term consolidation on affix acquisition by comparing knowledge of learned affixes two days and nearly two months after training. Results demonstrated that episodic knowledge of affixes can be acquired shortly after a single training session using either form or semantic learning, but suggested that the development of lexicalized representations of affixes requires the provision of semantic information during learning as well as a substantial period of offline consolidation.     

Cross-modal working memory binding and L1-L2 word learning

The ability to create temporary binding representations of information from different sources in working memory has recently been found to relate to the development of monolingual word recognition in children. The current study explored this possible relationship in an adult word-learning context. We assessed whether the relationship between cross-modal working memory binding and lexical development would be observed in the learning of associations between unfamiliar spoken words and their semantic referents, and whether it would vary across experimental conditions in first- and second-language word learning. A group of English monolinguals were recruited to learn 24 spoken disyllable Mandarin Chinese words in association with either familiar or novel objects as semantic referents. They also took a working memory task in which their ability to temporarily bind auditory-verbal and visual information was measured. Participants’ performance on this task was uniquely linked to their learning and retention of words for both novel objects and for familiar objects. This suggests that, at least for spoken language, cross-modal working memory binding might play a similar role in second language-like (i.e., learning new words for familiar objects) and in more native-like situations (i.e., learning new words for novel objects). Our findings provide new evidence for the role of cross-modal working memory binding in L1 word learning and further indicate that early stages of picture-based word learning in L2 might rely on similar cognitive processes as in L1.     

Phonological similarity neighborhoods and children’s short-term memory: Typical development and dyslexia

In this article, we explore whether structural characteristics of the phonological lexicon affect serial recall in typically developing and dyslexic children. Recent work has emphasized the importance of long-term phonological representations in supporting short-term memory performance. This occurs via redintegration (reconstruction) processes, which show significant neighborhood density effects in adults. We assessed whether serial recall in children was affected by neighborhood density in word and nonword tasks. Furthermore, we compared dyslexic children with typically developing children of the same age or reading level. Dyslexic children are held to have impaired phonological representations of lexical items. These impaired representations may impair or prevent the use of long-term phonological representations to redintegrate short-term memory traces. We report significant rime neighborhood density effects for serial recall of both words and nonwords, for both dyslexic and typically developing children.     

Modelling the effects of semantic ambiguity in word recognition

Most words in English are ambiguous between different interpretations; words can mean different things in different contexts. We investigate the implications of different types of semantic ambiguity for connectionist models of word recognition. We present a model in which there is competition to activate distributed semantic representations. The model performs well on the task of retrieving the different meanings of ambiguous words, and is able to simulate data reported by Rodd, Gaskell, and Marslen-Wilson [J. Mem. Lang. 46 (2002) 245] on how semantic ambiguity affects lexical decision performance. In particular, the network shows a disadvantage for words with multiple unrelated meanings (e.g., bark) that coexists with a benefit for words with multiple related word senses (e.g., twist). The ambiguity disadvantage arises because of interference between the different meanings, while the sense benefit arises because of differences in the structure of the attractor basins formed during learning. Words with few senses develop deep, narrow attractor basins, while words with many senses develop shallow, broad basins. We conclude that the mental representations of word meanings can be modelled as stable states within a high-dimensional semantic space, and that variations in the meanings of words shape the landscape of this space.     

New Word Acquisition in Children: Examining the Contribution of Verbal Short‐term Memory to Lexical and Semantic Levels of Learning

A variety of evidence suggests that human vocabulary acquisition and verbal short‐term ability are related. The aim of this study was to investigate the learning of new lexical and semantic representation in 7 to 12 years old children selected on the basis of their poor working memory capacity. A deep characterization of the short‐term memory (STM) capacities has been carried out through a series of tasks derived from recent STM models tapping STM, language and attentional processes. Participants experienced a three conditions word learning task designed to reflect lexical learning, semantic learning and lexical–semantic learning capacities. Other aspects of the learning such as the learning rate and the word length effect were evaluated. The experimental participants scored more poorly than controls on lexical learning, and this deficit was associated with the serial order STM and the attentional capacities. The current study also highlighted that neither the experimental group nor the control group took advantage in lexical learning of semantic information supplement. Our results suggest that children with verbal STM problems learn a smaller number of new words but present a similar way of learning than children without verbal STM problems. Copyright © 2013 John Wiley & Sons, Ltd.     

Objects and properties: A study of the breakdown of semantic memory

Abstract

This paper reports a study of the breakdown of semantic memory in the case of a subject with semantic dementia. The first experiment shows that the subject failed to comprehend words of low familiarity and word frequency, even though the spoken word forms were recognised as familiar. Experiments 2 and 3 showed (a) that the recall of word meanings in definition tasks did not vary with the generality of the word meaning (e.g. category, basic level, or subordinate property) but varied instead with the concept familiarity and frequency of the name; (b) that the ability to verify properties of basic-level objects was not affected by the ability to comprehend the property name, but depended instead on the degree of knowledge demonstrated for the object name in definition tasks; (c) that properties were frequently verified correctly when the object had been defined only to the superordinate level. It is argued that the results do not support the widely held view that, in general, specific information is lost first when semantic memory breaks down. The selective failure to recall specific information for some word meanings is discussed with reference to two theoretical accounts.     

Beginning readers activate semantics from sub-word orthography

Two experiments assessed whether 7-year-old children activate semantic information from sub-word orthography. Children made category decisions to visually-presented words, some of which contained an embedded word (e.g., hip in ship). In Experiment 1 children were slower and less accurate to classify words if they contained an embedded word related in meaning to the category (e.g., slower to reject ship as a ‘body part’ than an ‘animal’), especially when the embedded word was higher in frequency than the carrier word. This demonstrates that young children activate semantic information from sub-word orthographic representations, and that they do so from the relatively early stages of learning to read. Experiment 2 replicated this effect. Furthermore, we observed semantic interference regardless of whether the embedded word shared its pronunciation with the carrier (e.g., the hip in ship) or not (e.g., the crow in crown), and regardless of its position within the carrier, suggesting that interference was not dependent on phonological mediation. These findings show that by 7-years-of age, children have begun to establish an orthographic system that is capable of activating sub-word orthographic patterns, strong enough to connect with meaning, when reading words silently.