An associative account of the development of word learning

Word learning is a notoriously difficult induction problem because meaning is underdetermined by positive examples. How do children solve this problem? Some have argued that word learning is achieved by means of inference: young word learners rely on a number of assumptions that reduce the overall hypothesis space by favoring some meanings over others. However, these approaches have difficulty explaining how words are learned from conversations or text, without pointing or explicit instruction. In this research, we propose an associative mechanism that can account for such learning. In a series of experiments, 4-year-olds and adults were presented with sets of words that included a single nonsense word (e.g. dax). Some lists were taxonomic (i.,e., all items were members of a given category), some were associative (i.e., all items were associates of a given category, but not members), and some were mixed. Participants were asked to indicate whether the nonsense word was an animal or an artifact. Adults exhibited evidence of learning when lists consisted of either associatively or taxonomically related items. In contrast, children exhibited evidence of word learning only when lists consisted of associatively related items. These results present challenges to several extant models of word learning, and a new model based on the distinction between syntagmatic and paradigmatic associations is proposed.     

The dynamic functions of social cues during children's word learning

Children learn words in a social environment, facilitated in part by social cues from caregivers, such as eye-gaze and gesture. A common assumption is that social cues convey either perceptual or social information, depending on the age of the child. In this review of research on word learning and social cues during early childhood, we propose that (1) the functions of social cues are not categorically perceptual or social, and (2) social cues support word learning in four interdependent ways: by helping children to orient attention, extract relevant information, disambiguate referents, and understand others' referential intent. We conclude with specific recommendations for theory-building and suggest that the dynamic and complex functions of social cues need to be accounted for in any complete theory of word learning.     

Associative history affects the associative change undergone by both presented and absent cues in human causal learning

R. A. Rescorla (2000) noted that a number of influential theories of associative learning do not take the associative history of cues (i.e., the prior training that they have received) into account when calculating the associative change undergone by those cues. The authors tested this assumption in a human causal learning paradigm and found associative history to be an important determinant of the learning undergone by cues that are presented on a trial. Moreover, associative history was also found to influence the amount of retrospective revaluation undergone by absent cues. These findings conflict with models of causal learning in which the associative change undergone by an element of a cue compound is governed by a summed error term (e.g., R. A. Rescorla & A. R. Wagner, 1972).     

Asymmetries in cue competition in forward and backward blocking designs: Further evidence for causal model theory

A hallmark feature of elemental associative learning theories is that multiple cues compete for associative strength when presented with an outcome. Cue competition effects have been observed in humans, both in forward and in backward blocking procedures (e.g., Shanks, 1985) and are often interpreted as evidence for an associative account of human causal learning (e.g., Shanks & Dickinson, 1987). Waldmann and Holyoak (1992), however, demonstrated that cue competition only occurs in predictive, and not diagnostic, learning paradigms. While unexplainable from an associative perspective, this asymmetry readily follows from structural considerations of causal model theory. In this paper, we show that causal models determine the extent of cue competition not only in forward but also in backward blocking designs. Implications for associative and inferential accounts of causal learning are discussed.     

A Bootstrapping Model of Frequency and Context Effects in Word Learning

Prior research has shown that people can learn many nouns (i.e., word–object mappings) from a short series of ambiguous situations containing multiple words and objects. For successful cross‐situational learning, people must approximately track which words and referents co‐occur most frequently. This study investigates the effects of allowing some word‐referent pairs to appear more frequently than others, as is true in real‐world learning environments. Surprisingly, high‐frequency pairs are not always learned better, but can also boost learning of other pairs. Using a recent associative model (Kachergis, Yu, & Shiffrin, 2012), we explain how mixing pairs of different frequencies can bootstrap late learning of the low‐frequency pairs based on early learning of higher frequency pairs. We also manipulate contextual diversity, the number of pairs a given pair appears with across training, since it is naturalistically confounded with frequency. The associative model has competing familiarity and uncertainty biases, and their interaction is able to capture the individual and combined effects of frequency and contextual diversity on human learning. Two other recent word‐learning models do not account for the behavioral findings.     

学习不良儿童的元认知偏差：内部线索的影响

通过改变实验材料内部线索,旨在考察内部线索在学习不良儿童元认知偏差形成过程中的影响。实验1发现,学习不良儿童低关联字对的元认知偏差显著高于一般儿童,关联强度对学习判断的影响显著小于对测试成绩的影响;实验2发现,学习不良儿童反向方向字对的元认知偏差显著高于一般儿童,关联方向对学习判断的影响显著小于对测试成绩的影响。综合以上研究发现,相对一般儿童,学习不良儿童存在更大的元认知偏差,内部线索对学习判断和测试成绩的影响不一致模式适用于两组儿童。     

Not all is forgotten: Children's associative matrices for features of a word learning episode

Word learning studies traditionally examine the narrow link between words and objects, indifferent to the rich contextual information surrounding objects. This research examined whether children attend to this contextual information and construct an associative matrix of the words, objects, people, and environmental context during word learning. In Experiment 1, preschool-aged children (age: 3;2–5;11 years) were presented with novel words and objects in an animated storybook. Results revealed that children constructed associations beyond words and objects. Specifically, children attended to and had the strongest associations for features of the environmental context but failed to learn word-object associations. Experiment 2 demonstrated that children (age: 3;0–5;8 years) leveraged strong associations for the person and environmental context to support word-object mapping. This work demonstrates that children are especially sensitive to the word learning context and use associative matrices to support word mapping. Indeed, this research suggests associative matrices of the environment may be foundational for children's vocabulary development.     

Aging and retrospective revaluation of causal learning

In a 2-stage causal learning task, young and older participants first learned which foods presented in compound were followed by an allergic reaction (e.g., STEAK-BEANS→ REACTION) and then the causal efficacy of 1 food from these compounds was revalued (e.g., BEANS→ NO REACTION). In Experiment 1, unrelated food pairs were used, and although there were no age differences in compound- or single-cue-outcome learning, older adults did not retrospectively revalue the causal efficacy of the absent target cues (e.g., STEAK). However, they had weaker within-compound associations for the unrelated foods, and this may have prevented them from retrieving the representations of these cues. In Experiment 2, older adults still showed no retrospective revaluation of absent cues even though compound food cues with pre-existing associations were used (e.g., STEAK-POTATO), and they received additional learning trials. Finally, in Experiment 3, older adults revalued the causal efficacy of the target cues when small, unobtrusive icons of these cues were present during single-cue revaluation. These findings suggest that age-related deficits in causal learning for absent cues are due to ineffective associative binding and reactivation processes.     

Social cues modulate the representations underlying cross-situational learning

Because children hear language in environments that contain many things to talk about, learning the meaning of even the simplest word requires making inferences under uncertainty. A cross-situational statistical learner can aggregate across naming events to form stable word-referent mappings, but this approach neglects an important source of information that can reduce referential uncertainty: social cues from speakers (e.g., eye gaze). In four large-scale experiments with adults, we tested the effects of varying referential uncertainty in cross-situational word learning using social cues. Social cues shifted learners away from tracking multiple hypotheses and towards storing only a single hypothesis (Experiments 1 and 2). In addition, learners were sensitive to graded changes in the strength of a social cue, and when it became less reliable, they were more likely to store multiple hypotheses (Experiment 3). Finally, learners stored fewer word-referent mappings in the presence of a social cue even when given the opportunity to visually inspect the objects for the same amount of time (Experiment 4). Taken together, our data suggest that the representations underlying cross-situational word learning of concrete object labels are quite flexible: In conditions of greater uncertainty, learners store a broader range of information.     

The emergence of words: attentional learning in form and meaning

Children improve at word learning during the 2nd year of life—sometimes dramatically. This fact has suggested a change in mechanism, from associative learning to a more referential form of learning. This article presents an associative exemplar-based model that accounts for the improvement without a change in mechanism. It provides a unified account of children's growing abilities to (a) learn a new word given only 1 or a few training trials ("fast mapping"); (b) acquire words that differ only slightly in phonological form; (c) generalize word meanings preferentially along particular dimensions, such as object shape (the "shape bias"); and (d) learn 2nd labels for already-named objects, despite a persisting resistance to doing so ("mutual exclusivity"). The model explains these improvements in terms of increased attention to relevant aspects of form and meaning, which reduces memory interference. The interaction of associations and reference in word learning is discussed.     

Dynamic self-organization and early lexical development in children

In this study we present a self-organizing connectionist model of early lexical development. We call this model DevLex-II, based on the earlier DevLex model. DevLex-II can simulate a variety of empirical patterns in children's acquisition of words. These include a clear vocabulary spurt, effects of word frequency and length on age of acquisition, and individual differences as a function of phonological short-term memory and associative capacity. Further results from lesioned models indicate developmental plasticity in the network's recovery from damage, in a non-monotonic fashion. We attribute the network's abilities in accounting for lexical development to interactive dynamics in the learning process. In particular, variations displayed by the model in the rate and size of early vocabulary development are modulated by (a) input characteristics, such as word frequency and word length, (b) consolidation of lexical-semantic representation, meaning-form association, and phonological short-term memory, and (c) delayed processes due to interactions among timing, severity, and recoverability of lesion. Together, DevLex and DevLex-II provide an accurate computational account of early lexical development.     

Use of phonetic specificity during the acquisition of new words: differences between consonants and vowels

The present study explores the issue of the use of phonetic specificity in the process of learning new words at 20 months of age. The procedure used follows Nazzi and Gopnik [Nazzi, T., & Gopnik, A. (2001). Linguistic and cognitive abilities in infancy: When does language become a tool for categorization? Cognition, 80, B11-B20]. Infants were first presented with triads of perceptually dissimilar objects, which were given made-up names, two of the objects receiving the same name. Then, word learning was evaluated through object selection/categorization. Tests involved phonetically different words (e.g. [pize] vs. [mora], Experiment 1), words differing minimally on their onset consonant (e.g. [pize] vs. [tize], Experiment 2a), and conditions which had never been tested before: non-initial consonantal contrasts (e.g. [pide] vs. [pige], Experiment 2b), and vocalic contrasts (e.g. [pize] vs. [pyze]; [pize] vs. [paze]; [pize] vs. [pizu], Experiments 3a-c). Results differed across conditions: words could be easily learnt in the phonetically different condition, and were learnt, though to a lesser degree, in both the initial and non-initial minimal consonant contrast; however, infants' global performance on all three vocalic contrasts was at chance level. The present results shed new light regarding the specificity of early words, and raise the possibility of different contributions for vowels and consonants in early word learning.     

Imageability,age of acquisition,and frequency factors in acronym comprehension

In spite of their unusual orthographic and phonological form, acronyms (e.g., BBC, HIV, NATO) can become familiar to the reader, and their meaning can be accessed well enough that they are understood. The factors in semantic access for acronym stimuli were assessed using a word association task. Two analyses examined the time taken to generate a word association response to acronym cues. Responses were recorded more quickly to cues that elicited a large proportion of semantic responses, and those that were high in associative strength. Participants were shown to be faster to respond to cues which were imageable or early acquired. Frequency was not a significant predictor of word association responses. Implications for theories of lexical organisation are discussed.     

Developmental differences in children's context-dependent word learning

In this study, 2.5-, 3-, and 4-year-olds (N = 108) participated in a novel noun generalization task in which background context was manipulated. During the learning phase of each trial, children were presented with exemplars in one or multiple background contexts. At the test, children were asked to generalize to a novel exemplar in either the same or a different context. The 2.5-year-olds’ performance was supported by matching contexts; otherwise, children in this age group demonstrated context dependent generalization. The 3-year-olds’ performance was also supported by matching contexts; however, children in this age group were aided by training in multiple contexts as well. Finally, the 4-year-olds demonstrated high performance in all conditions. The results are discussed in terms of the relationship between word learning and memory processes; both general memory development and memory developments specific to word learning (e.g., retention of linguistic labels) are likely to support word learning and generalization.     

Infants’ statistical word segmentation in an artificial language is linked to both parental speech input and reported production abilities

Individual variability in infant's language processing is partly explained by environmental factors, like the quantity of parental speech input, as well as by infant‐specific factors, like speech production. Here, we explore how these factors affect infant word segmentation. We used an artificial language to ensure that only statistical regularities (like transitional probabilities between syllables) could cue word boundaries, and then asked how the quantity of parental speech input and infants’ babbling repertoire predict infants’ abilities to use these statistical cues. We replicated prior reports showing that 8‐month‐old infants use statistical cues to segment words, with a preference for part‐words over words (a novelty effect). Crucially, 8‐month‐olds with larger novelty effects had received more speech input at 4 months and had greater production abilities at 8 months. These findings establish for the first time that the ability to extract statistical information from speech correlates with individual factors in infancy, like early speech experience and language production. Implications of these findings for understanding individual variability in early language acquisition are discussed.     

Revise and resubmit: How real-time parsing limitations influence grammar acquisition

We present the results from a three-day artificial language learning study on adults. The study examined whether sentence-parsing limitations, in particular, difficulties revising initial syntactic/semantic commitments during comprehension, shape learners’ ability to acquire a language. Findings show that both comprehension and production of morphology pertaining to sentence argument structure are delayed when this morphology consistently appears at the end, rather than at the beginning, of sentences in otherwise identical grammatical systems. This suggests that real-time processing constraints impact acquisition; morphological cues that tend to guide linguistic analyses are easier to learn than cues that revise these analyses. Parallel performance in production and comprehension indicates that parsing constraints affect grammatical acquisition, not just real-time commitments. Properties of the linguistic system (e.g., ordering of cues within a sentence) interact with the properties of the cognitive system (cognitive control and conflict-resolution abilities) and together affect language acquisition.     

Learning words’ sounds before learning how words sound: 9-Month-olds use distinct objects as cues to categorize speech information

One of the central themes in the study of language acquisition is the gap between the linguistic knowledge that learners demonstrate, and the apparent inadequacy of linguistic input to support induction of this knowledge. One of the first linguistic abilities in the course of development to exemplify this problem is in speech perception: specifically, learning the sound system of one’s native language. Native-language sound systems are defined by meaningful contrasts among words in a language, yet infants learn these sound patterns before any significant numbers of words are acquired. Previous approaches to this learning problem have suggested that infants can learn phonetic categories from statistical analysis of auditory input, without regard to word referents. Experimental evidence presented here suggests instead that young infants can use visual cues present in word-labeling situations to categorize phonetic information. In Experiment 1, 9-month-old English-learning infants failed to discriminate two non-native phonetic categories, establishing baseline performance in a perceptual discrimination task. In Experiment 2, these infants succeeded at discrimination after watching contrasting visual cues (i.e., videos of two novel objects) paired consistently with the two non-native phonetic categories. In Experiment 3, these infants failed at discrimination after watching the same visual cues, but paired inconsistently with the two phonetic categories. At an age before which memory of word labels is demonstrated in the laboratory, 9-month-old infants use contrastive pairings between objects and sounds to influence their phonetic sensitivity. Phonetic learning may have a more functional basis than previous statistical learning mechanisms assume: infants may use cross-modal associations inherent in social contexts to learn native-language phonetic categories.     

Books Received From August 1, 2010 to July 31, 2011

Word learning is a lifelong activity constrained by cognitive biases that people possess at particular points in development. Age of acquisition (AoA) is a psycholinguistic variable that may prove useful toward gauging the relative weighting of different phonological, semantic, and morphological factors at different phases of language acquisition and development. Our aim here was to evaluate AoA as a statistical tool for taking “snapshots” of cognitive development. We examined a large corpus of English nouns (n = 1,381) with AoA as the outcome variable in three separate multivariate regressions, encompassing different age ranges (early–middle–late). Predictors included perceptual (e.g., imagery), phonological (e.g., phonological neighborhood density), and lexical (e.g., word length) factors. Different combinations of predictors accounted for significant proportions of the variance for different AoA ranges (i.e., early–middle–late). For example, imageability and frequency are stronger predictors of early relative to late word learning. These corpus analyses support a hybrid model of word learning in which multiple perceptual and linguistic factors are differentially weighted over time. This statistical approach may provide independent corroboration of and motivation for experimental studies in language learning and cognitive development.     

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.     

Baby Wordsmith

ABSTRACT— How do infants acquire their first words? Word reference , or how words map onto objects and events, lies at the core of this question. The emergentist coalition model (ECM) represents a new wave of hybrid developmental theories suggesting that the process of vocabulary development changes from one based in perceptual salience and association to one embedded in social understanding. Beginning at 10 months, babies learn words associatively, ignoring the speaker's social cues and using perceptual salience to guide them. By 12 months, babies attend to social cues, but fail to recruit them for word learning. By 18 and 24 months, babies recruit speakers' social cues to learn the names of particular objects speakers label, regardless of those objects' perceptual attraction. Controversies about how to account for the changing character of word acquisition, along with the roots of children's increasing reliance on speakers' social intent, are discussed.