Effects of visual information on adults' and infants' auditory statistical learning

Infant and adult learners are able to identify word boundaries in fluent speech using statistical information. Similarly, learners are able to use statistical information to identify word-object associations. Successful language learning requires both feats. In this series of experiments, we presented adults and infants with audio-visual input from which it was possible to identify both word boundaries and word-object relations. Adult learners were able to identify both kinds of statistical relations from the same input. Moreover, their learning was actually facilitated by the presence of two simultaneously present relations. Eight-month-old infants, however, do not appear to benefit from the presence of regular relations between words and objects. Adults, like 8-month-olds, did not benefit from regular audio-visual correspondences when they were tested with tones, rather than linguistic input. These differences in learning outcomes across age and input suggest that both developmental and stimulus-based constraints affect statistical learning.     

Sensitivity to sampling in Bayesian word learning

We report a new study testing our proposal that word learning may be best explained as an approximate form of Bayesian inference (Xu & Tenenbaum, in press). Children are capable of learning word meanings across a wide range of communicative contexts. In different contexts, learners may encounter different sampling processes generating the examples of word-object pairings they observe. An ideal Bayesian word learner could take into account these differences in the sampling process and adjust his/her inferences about word meaning accordingly. We tested how children and adults learned words for novel object kinds in two sampling contexts, in which the objects to be labeled were sampled either by a knowledgeable teacher or by the learners themselves. Both adults and children generalized more conservatively in the former context; that is, they restricted the label to just those objects most similar to the labeled examples when the exemplars were chosen by a knowledgeable teacher, but not when chosen by the learners themselves. We discuss how this result follows naturally from a Bayesian analysis, but not from other statistical approaches such as associative word-learning models.     

Infants' reasoning about opaque and transparent occluders in an individuation task

Two experiments document that conceptual knowledge influences 3-year-olds' extension of novel words. In Experiment 1, when objects were described as having conceptual properties typical of artifacts, children extended novel labels for these objects on the basis of shape alone. When the very same objects were described as having conceptual properties typical of animate kinds, children extended novel labels for these objects on the basis of both shape and texture. Moreover, providing a salient perceptual cue (Experiment 2) did not interfere with children's reliance on conceptual information in extending novel words: when an object with eyes was labeled with a novel word in the context of a story describing the object as an artifact, children extended the label on the basis of shape alone (i.e. as though the object were an artifact). These results, which challenge directly the position that 'dumb attentional mechanisms' can account for word learning, stand as evidence for the central role of conceptual information in mapping words to meaning.     

The power of the written word: Comparing word meaning inferencing from auditory and written modalities throughout grade school

Previous research indicates that word learning from auditory contexts may be more effective than written context at least through fourth grade. However, no study has examined contextual differences in word learning in older school-aged children when reading abilities are more developed. Here we examined developmental differences in children’s ability to deduce the meanings of unknown words from the surrounding linguistic context in the auditory and written modalities and sought to identify the most important predictors of success in each modality. A total of 89 children aged 8–15 years were randomly assigned to either read or listen to a narrative that included eight novel words, with five exposures to each novel word. They then completed three posttests to assess word meaning inferencing. Children across all ages performed better in the written modality. Vocabulary was the only significant predictor of success on the word inferencing task. Results indicate support for written stimuli as the most effective modality for novel word meaning deduction. Our findings suggest that the presence of orthographic information facilitates novel word learning even for early, less proficient readers.     

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.     

Learning of syllable-object relations by preverbal infants: The role of temporal synchrony and syllable distinctiveness

The role of temporal synchrony and syllable distinctiveness in preverbal infants’ learning of word-object relations was investigated. In Experiment 1, 7- and 8-month-olds (N = 64) were habituated under conditions where two similar-sounding syllables, /tah/ and /gah/, were spoken simultaneously with the motions of one of two sets of objects (synchronous) or out of phase with the motions (asynchronous). On test trials, 8-month-olds, but not 7-month-olds, showed learning of the relations in the synchronous condition but not in the asynchronous condition. Furthermore, in Experiment 2, following habituation to one of the synchronous syllable-object pairs, 7-month-olds (n = 8) discriminated the syllables and the objects. In Experiment 3, following habituation to two distinct syllables, /tah/-/gih/ or /gah/-/tih/, paired with identical objects, 7-month-olds (n = 40) showed learning of the relations, again only in the synchronous condition. Thus, synchrony, which mothers naturally provide between words and object motions, facilitated the mapping onto objects of similar-sounding syllables at 8 months of age and distinct syllables at 7 months of age. These findings suggest an interaction between infants’ synchrony and syllable distinctiveness perception during early word mapping development.     

Class matters: 12‐month‐olds’ word–object associations privilege content over function words

A fundamental step in learning words is the development of an association between a sound pattern and an element in the environment. Here we explore the nature of this associative ability in 12‐month‐olds, examining whether it is constrained to privilege particular word forms over others. Forty‐eight infants were presented with sets of novel English content‐like word–object pairings (e.g. fep) or novel English function‐like word–object (e.g. iv) pairings until they habituated. Results indicated that infants associated novel content‐like words, but not the novel function‐like words, with novel objects. These results demonstrate that the mechanism with which basic word–object associations are formed is remarkably sophisticated by the onset of productive language. That is, mere associative pairings are not sufficient to form mappings. Rather the system requires well‐formed noun‐like words to co‐occur with objects in order for the linkages to arise.     

Context effects on orthographic learning of regular and irregular words

The self-teaching hypothesis proposes that orthographic learning takes place via phonological decoding in meaningful texts, that is, in context. Context is proposed to be important in learning to read, especially when decoding is only partial. However, little research has directly explored this hypothesis. The current study looked at the effect of context on orthographic learning and examined whether there were different effects for novel words given regular and irregular pronunciations. Two experiments were conducted using regular and irregular novel words, respectively. Second-grade children were asked to learn eight novel words either in stories or in a list of words. The results revealed no significant effect of context for the regular items. However, in an orthographic decision task, there was a facilitatory effect of context on irregular novel word learning. The findings support the view that contextual information is important to orthographic learning, but only when the words to be learned contain irregular spelling-sound correspondences.     

Pre- and postlexical loci of contextual effects on word recognition

The context in which a word occurs could influence either the actual decoding of the word or a postrecognition judgment of the relatedness of word and context. In this research, we investigated the loci of contextual effects that occur in lexical priming, when prime and target words are related along different dimensions. Both lexical decision and naming tasks were used because previous research had suggested that they are differentially sensitive to postlexical processing. Semantic and associative priming occurred with both tasks. Other facilitative contextual effects, due to syntactic relations between words, backward associations, or changes in the proportion of related items, occurred only with the lexical decision task. The results indicate that only associative and semantic priming facilitate the decoding of a target; the other effects are postlexical. The results are related to the different demands of the naming and lexical decision tasks, and to current models of word recognition.     

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.     

Priming of new associations in reading time: What is learned?

The priming of new associations has been a controversial topic, with some studies finding significant effects but others failing to replicate these results. Three studies investigated the priming of new associations in a reading time task, presenting lists of word pairs that were read aloud as quickly as possible. In Experiment 1, significant priming of new associations was found after two study presentations, replicating similar results by Moscovitch, Winocur, and MacLachan (1986). In Experiment 2, reading time was facilitated for intact pairs when word positions remained constant relative to when word positions were reversed. This suggested that the associative priming effect was related to specific lower level features of the word pairs rather than to abstract associations. In Experiment 3, the insertion of the wordand between test words eliminated the pairing-specific effect, placing the locus of new association priming at the transition between words within pairs. These findings demonstrate that the knowledge that supports priming of new associations in the reading time task involves perceptual or articulatory information about the transitions between words rather than abstract associative knowledge.     

Bidirectional priming in infants

In associative priming, the direct activation of one concept indirectly activates others that are associated with it, depending on the directionality of the association. We asked whether associative priming in preverbal infants is bidirectional. Infants associated a puppet imitation task with an operant train task by watching an adult model target actions on the puppet in the incidental context of the train. Later, priming of the forgotten memory of the train task reactivated the infants' memory of the puppet task (Experiment 1), and priming of the infants' forgotten memory of the puppet task reactivated their memory of the train task (Experiment 2). The finding that associative priming was bidirectional offers new insights into the nature of the mnemonic networks formed early in infancy. Additionally, the fact that the present association was formed rapidly and incidentally suggests that a fast mapping, general learning mechanism, like that posited to mediate word-object learning, was responsible for its encoding.     

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.     

Infants track word forms in early word–object associations

A central component of language development is word learning. One characterization of this process is that language learners discover objects and then look for word forms to associate with these objects (Mcnamara, 1984 ; Smith, 2000 ). Another possibility is that word forms themselves are also important, such that once learned, hearing a familiar word form will lead young word learners to look for an object to associate with it (Juscyzk, 1997 ). This research investigates the relative weighing of word forms and objects in early word–object associations using the anticipatory eye‐movement paradigm (AEM; McMurray & Aslin, 2004 ). Eighteen‐month‐old infants and adults were taught novel word–object associations and then tested on ambiguous stimuli that pitted word forms and objects against each other. Results revealed a change in weighing of these components across development. For 18‐month‐old infants, word forms weighed more in early word–object associative learning, while for adults, objects were more salient. Our results suggest that infants preferentially use word forms to guide the process of word–object association.     

Background context affects word-object mapping

Children encounter new words across variable and noisy contexts. This variability may affect word learning, but the literature includes discrepant findings. The current experiment investigated one source of these discrepant findings: whether contexts with familiar, nameable objects are associated with less robust label learning. Two year olds were exposed to word-object pairings on variable contexts that either included nameable objects or did not. Target selection was more robust when exposure occurred without other nameable objects. The difference was present immediately, but not after a delay. This study provides the evidence that context effects are context-bound.     

Twelve-month-olds privilege words over other linguistic sounds in an associative learning task

We examined whether 12-month-old infants privilege words over other linguistic stimuli in an associative learning task. Sixty-four infants were presented with sets of either word–object, communicative sound–object, or consonantal sound–object pairings until they habituated. They were then tested on a ‘switch’ in the sound to determine whether they were able to associate the word and/or sound with the novel objects. Infants associated words, but not communicative sounds or consonantal sounds, with novel objects. The results demonstrate that infants exhibit a preference for words over other linguistic stimuli in an associative word learning task. This suggests that by 12 months of age, infants have developed knowledge about the nature of an appropriate sound form for an object label and will privilege this form as an object label.     

Contextual repetition facilitates word learning via fast mapping

The current study explores whether contextual repetition during fast mapping facilitates word learning. Three-year-old children completed fast mapping and test trials using a touchscreen computer. For half of the children, the non-targets (competitors) repeated across learning trials and for other children there was no repetition. All children received the same test trials. Children who experienced contextual repetition, that is, children for whom the competitors repeated during the initial fast mapping task, demonstrated word learning. These data demonstrate that children's word learning is facilitated by the presence of extraneous yet predictable information in the initial fast mapping task.     

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.     

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.     

Expectancy,integration, and interactional processes: Age differences in the nature of words affected by sentence context

Two experiments investigated sentence context effects on the naming times of sentence completion words by third-grade children and college students. Across both experiments, the largest age difference in contextual facilitation was obtained for highly predictable, best completion words. Pronounced age differences in facilitation effects were also present for semantically acceptable target words which were much less predictable in the sentence context than the best completion words. However, age differences in contextual facilitation were negligible for target words which were associatively related to the best completion word, but which were not also semantically acceptable in the sentence context. Thus, the semantic acceptability of the word in the sentence context had a much greater influence on children's as compared to adults' word identification times, both when the word was highly predictable, as well as when it was much less predictable in the sentence context.