Embodied attention and word learning by toddlers

Many theories of early word learning begin with the uncertainty inherent to learning a word from its co-occurrence with a visual scene. However, the relevant visual scene for infant word learning is neither from the adult theorist's view nor the mature partner's view, but is rather from the learner's personal view. Here we show that when 18-month old infants interacted with objects in play with their parents, they created moments in which a single object was visually dominant. If parents named the object during these moments of bottom-up selectivity, later forced-choice tests showed that infants learned the name, but did not when naming occurred during a less visually selective moment. The momentary visual input for parents and toddlers was captured via head cameras placed low on each participant's forehead as parents played with and named objects for their infant. Frame-by-frame analyses of the head camera images at and around naming moments were conducted to determine the visual properties at input that were associated with learning. The analyses indicated that learning occurred when bottom-up visual information was clean and uncluttered. The sensory-motor behaviors of infants and parents were also analyzed to determine how their actions on the objects may have created these optimal visual moments for learning. The results are discussed with respect to early word learning, embodied attention, and the social role of parents in early word learning.     

The role of novelty in early word learning

What mechanism implements the mutual exclusivity bias to map novel labels to objects without names? Prominent theoretical accounts of mutual exclusivity (e.g., Markman, 1989, 1990 ) propose that infants are guided by their knowledge of object names. However, the mutual exclusivity constraint could be implemented via monitoring of object novelty (see Merriman, Marazita, & Jarvis, 1995 ). We sought to discriminate between these contrasting explanations across two preferential looking experiments with 22‐month‐olds. In Experiment 1, infants viewed three objects: one name‐known, two name‐unknown. Of the two name‐unknown objects, one was novel, and the other had been previously familiarized. The infants responded to hearing a novel label by increasing attention only to the novel, name‐unknown object. In a second experiment in which the name‐known object was absent, a novel label increased infants’ attention to a novel object beyond baseline preference for novelty. The experiments provide clear evidence for a novelty‐based mechanism. However, differences in the time course of disambiguation across experiments suggest that novelty processing may be influenced by contextual factors.     

Speaker variability augments phonological processing in early word learning

Infants in the early stages of word learning have difficulty learning lexical neighbors (i.e. word pairs that differ by a single phoneme), despite their ability to discriminate the same contrast in a purely auditory task. While prior work has focused on top‐down explanations for this failure (e.g. task demands, lexical competition), none has examined if bottom‐up acoustic‐phonetic factors play a role. We hypothesized that lexical neighbor learning could be improved by incorporating greater acoustic variability in the words being learned, as this may buttress still‐developing phonetic categories, and help infants identify the relevant contrastive dimension. Infants were exposed to pictures accompanied by labels spoken by either a single or multiple speakers. At test, infants in the single‐speaker condition failed to recognize the difference between the two words, while infants who heard multiple speakers discriminated between them.     

The use of social and salience cues in early word learning

This article explores young infants' ability to learn new words in situations providing tightly controlled social and salience cues to their reference. Four experiments investigated whether, given two potential referents, 15-month-olds would attach novel labels to (a) an image toward which a digital recording of a face turned and gazed, (b) a moving image versus a stationary image, (c) a moving image toward which the face gazed, and (d) a gazed-on image versus a moving image. Infants successfully used the recorded gaze cue to form new word-referent associations and also showed learning in the salience condition. However, their behavior in the salience condition and in the experiments that followed suggests that, rather than basing their judgments of the words' reference on the mere presence or absence of the referent's motion, infants were strongly biased to attend to the consistency with which potential referents moved when a word was heard.     

"Shhh! We're tryin' to concentrate": attention and environmental distracters in novel word learning

The authors' purpose in this study was to evaluate the role of attention, as a central dimension of temperament, in children's real-time acquisition of novel vocabulary. Environmental distractions were administered to 47 22-month-old children as they acquired novel vocabulary in a fast-mapping task. Two distraction conditions impeded novel word acquisition, but only 1 impeded attention allocation. Attention allocation was correlated with novel word acquisition under conditions of distraction, but not in their absence. Results suggest that attention allocation is especially important for word learning under conditions of distraction. Given that in their day-to-day lives children often encounter new words amid a host of environmental distractions, children with constitutionally fewer attentional resources, such as temperamentally difficult children, may be at a vocabulary-learning disadvantage.     

First in,first out: Word learning age and spoken word frequency as predictors of word familiarity and word naming latency

This study is concerned with recent claims that subjective measures of word frequency are more suitable than are standard word frequency counts as indices of actual frequency of word encounter. A multiple regression study is reported, which shows that the major predictor of familiarity ratings is word learning age. Objective measures of spoken and written word frequency made independent contributions to the variance. It is concluded that rated familiarity is not an appropriate substitute for objective frequency measures. A multiple regression study of word naming latency is reported, and shows that rated word learning age is a better predictor of word naming latency than are spoken word frequency, written word frequency, rated familiarity, and other variables. Possible theoretical explanations for age-of-acquisition effects are discussed and it is concluded that early-learned words have a more complete representation in a phonological output lexicon. This conclusion is related to relevant developmental literature.     

Examining the role of social cues in early word learning

Infants watched a video of an adult pointing towards two different objects while hearing novel labels. Analyses indicated that 14- and 18-month-olds looked longer at the target object, but only 18-month-olds showed word learning. The results suggest that different types of social cues are available at different ages.     

Mechanisms underlying accent accommodation in early word learning: evidence for general expansion

Previous work reveals that toddlers can accommodate a novel accent after hearing it for only a brief period of time. A common assumption is that children, like adults, cope with nonstandard pronunciations by relying on words they know (e.g. ‘this person pronounces sock as sack, therefore by black she meant block’). In this paper, we assess whether toddlers might additionally use a general expansion strategy, whereby they simply accept non‐standard pronunciations when variability is expected. We exposed a group of 24‐month‐old English‐learning toddlers to variability in indexical cues (very diverse voices from native English talkers), and another to variability in social cues (very diverse‐looking silent actors); neither group was familiarized with the target novel accent. At test, both groups succeeded in recognizing a novel word when spoken in the novel accent. Thus, even when no lexical cues are available, variability can prepare young children for non‐standard pronunciations.     

Using variability to guide dimensional weighting: associative mechanisms in early word learning

At 14 months, children appear to struggle to apply their fairly well-developed speech perception abilities to learning similar sounding words (e.g., bih/dih; Stager & Werker, 1997). However, variability in nonphonetic aspects of the training stimuli seems to aid word learning at this age. Extant theories of early word learning cannot account for this benefit of variability. We offer a simple explanation for this range of effects based on associative learning. Simulations suggest that if infants encode both noncontrastive information (e.g., cues to speaker voice) and meaningful linguistic cues (e.g., place of articulation or voicing), then associative learning mechanisms predict these variability effects in early word learning. Crucially, this means that despite the importance of task variables in predicting performance, this body of work shows that phonological categories are still developing at this age, and that the structure of noninformative cues has critical influences on word learning abilities.     

Intentionality and word learning

Humans intuitively think about the actions of others in terms of mental states eliefs, desires, emotions and intentions. This 'theory of mind' plays a central role in how children learn the meanings of certain words. First, it underlies how they determine the reference of a novel word. When children hear a new object name (e.g. 'Look at the fendle'), they do not use spatio-temporal contiguity to determine what the word describes; instead they focus on cues to the referential intention of the speaker, such as direction of gaze. Second, an understanding of purpose and design is sometimes necessary to enable the child to understand the entities and actions that nouns and verbs refer to. This is particularly relevant for nouns that refer to collections of objects such as 'family' and 'game', and for verbs that refer to actions defined in terms of an actor's goals, such as 'give' and 'make'. Finally, intentional considerations partially underlie the generalization of names for artifact categories, such as 'chair' and 'clock', which can refer to entities of highly dissimilar appearance.     

Beyond naïve cue combination: salience and social cues in early word learning

Children learn their earliest words through social interaction, but it is unknown how much they rely on social information. Some theories argue that word learning is fundamentally social from its outset, with even the youngest infants understanding intentions and using them to infer a social partner's target of reference. In contrast, other theories argue that early word learning is largely a perceptual process in which young children map words onto salient objects. One way of unifying these accounts is to model word learning as weighted cue combination, in which children attend to many potential cues to reference, but only gradually learn the correct weight to assign each cue. We tested four predictions of this kind of naïve cue combination account, using an eye‐tracking paradigm that combines social word teaching and two‐alternative forced‐choice testing. None of the predictions were supported. We thus propose an alternative unifying account: children are sensitive to social information early, but their ability to gather and deploy this information is constrained by domain‐general cognitive processes. Developmental changes in children's use of social cues emerge not from learning the predictive power of social cues, but from the gradual development of attention, memory, and speed of information processing.     

Knowledge embedded in process: the self-organization of skilled noun learning

Young children's skilled generalization of newly learned nouns to new instances has become the battleground for two very different approaches to cognition. This debate is a proxy for a larger dispute in cognitive science and cognitive development: cognition as rule-like amodal propositions, on the one hand, or as embodied, modal, and dynamic processes on the other. After a brief consideration of this theoretical backdrop, we turn to the specific task set before us: an overview of the Attentional Learning Account (ALA) of children's novel noun generalizations, the constrained set of experimental results to be explained, and our explanation of them. We conclude with a consideration of what all of this implies for a theory of cognitive development.     

Taking stock as theories of word learning take shape

In this paper we consider the perceptual and conceptual contributions that shape early word learning, using research on the shape bias as a case in point. In our view, conceptual, linguistic, social-pragmatic, and perceptual sources of information influence one another powerfully and continuously in the service of word learning throughout infancy and early childhood. We articulate several key points of convergence and divergence between our theoretical perspective and that of the attentional learning account. Finally, we consider the broader implications of this debate for clarifying the forces that constrain development.     

Visual attention as a multilevel selection process

Natural visual scenes are cluttered and contain many different objects that cannot all be processed simultaneously. Therefore, attentional mechanisms are needed to select relevant and to filter out irrelevant information. Evidence from functional brain imaging reveals that attention operates at various processing levels within the visual system and beyond. First, the lateral geniculate nucleus appears to be the first stage in the processing of visual information that is modulated by attention, consistent with the idea that it may play an important role as an early gatekeeper in controlling neural gain. Second, areas at intermediate cortical-processing levels, such as V4 and TEO, appear to be important sites at which attention filters out unwanted information by means of receptive field mechanisms. Third, the attention mechanisms that operate in the visual system appear to be controlled by a distributed network of higher order areas in the frontal and parietal cortex, which generate top-down signals that are transmitted via feedback connections to the visual system. And fourth, the pulvinar of the thalamus may operate by integrating and coordinating attentional functions in concert with the fronto-parietal network, although much needs to be learned about its functional properties. The overall view that emerges from the studies reviewed in this article is that neural mechanisms of selective attention operate at multiple stages in the visual system and beyond and are determined by the visual processing capabilities of each stage. In this respect, attention can be considered in terms of a multilevel selection process.     

Learning nonwords: the Hebb repetition effect as a model of word learning

Page and Norris [(2008). Is there a common mechanism underlying word-form learning and the Hebb repetition effect? Experimental data and a modelling framework. In A. Thorn &; M. P. A. Page (Eds.), Interactions between short-term and long-term memory in the verbal domain; (2009). A model linking immediate serial recall, the Hebb repetition effect and the learning of phonological word forms. Philosophical Transactions of the Royal Society B: Biological Sciences, 364(1536), 3737–3753. doi:10.1098/rstb.2009.0173] have suggested that the Hebb [(1961). Distinctive features of learning in the higher animal. In J. F. Delafresnaye (Ed.), Brain mechanisms and learning (pp. 37–46). Oxford: Blackwell] repetition paradigm can be considered as a laboratory analogue of word learning. In Hebb learning experiments, the lists of items to be learned are presented as discrete sequences. In contrast, novel words are, by definition, always heard as a single coarticulated whole. Might this undermine the claim that Hebb learning can shed light on word learning? Here we report an experiment comparing learning sequences of isolated syllables with learning the same sequences spoken as a single coarticulated nonword. The pattern of learning was similar in the two cases, suggesting that the Hebb repetition paradigm can indeed provide valuable insights into the way novel word forms are learned.     

Detailed behavioral analysis as a window into cross-situational word learning

Recent research has demonstrated that word learners can determine word-referent mappings by tracking co-occurrences across multiple ambiguous naming events. The current study addresses the mechanisms underlying this capacity to learn words cross-situationally. This replication and extension of Yu and Smith (2007) investigates the factors influencing both successful cross-situational word learning and mis-mappings. Item analysis and error patterns revealed that the co-occurrence structure of the learning environment as well as the context of the testing environment jointly affected learning across observations. Learners also adopted an exclusion strategy, which contributed conjointly with statistical tracking to performance. Implications for our understanding of the processes underlying cross-situational word learning are discussed.