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.     

Infant sustained attention but not joint attention to objects at 9 months predicts vocabulary at 12 and 15 months

Vocabulary differences early in development are highly predictive of later language learning as well as achievement in school. Early word learning emerges in the context of tightly coupled social interactions between the early learner and a mature partner. In the present study, we develop and apply a novel paradigm—dual head‐mounted eye tracking—to record momentary gaze data from both parents and infants during free‐flowing toy‐play contexts. With fine‐grained sequential patterns extracted from continuous gaze streams, we objectively measure both joint attention and sustained attention as parents and 9‐month‐old infants played with objects and as parents named objects during play. We show that both joint attention and infant sustained attention predicted vocabulary sizes at 12 and 15 months, but infant sustained attention in the context of joint attention, not joint attention itself, is the stronger unique predictor of later vocabulary size. Joint attention may predict word learning because joint attention supports infant attention to the named object.     

Monolingual,bilingual, trilingual: infants' language experience influences the development of a word‐learning heuristic

How infants learn new words is a fundamental puzzle in language acquisition. To guide their word learning, infants exploit systematic word‐learning heuristics that allow them to link new words to likely referents. By 17 months, infants show a tendency to associate a novel noun with a novel object rather than a familiar one, a heuristic known as disambiguation. Yet, the developmental origins of this heuristic remain unknown. We compared disambiguation in 17‐ to 18‐month‐old infants from different language backgrounds to determine whether language experience influences its development, or whether disambiguation instead emerges as a result of maturation or social experience. Monolinguals showed strong use of disambiguation, bilinguals showed marginal use, and trilinguals showed no disambiguation. The number of languages being learned, but not vocabulary size, predicted performance. The results point to a key role for language experience in the development of disambiguation, and help to distinguish among theoretical accounts of its emergence.     

The origins of word learning: Brain responses of 3‐month‐olds indicate their rapid association of objects and words

The present study explored the origins of word learning in early infancy. Using event‐related potentials (ERP) we monitored the brain activity of 3‐month‐old infants when they were repeatedly exposed to several initially novel words paired consistently with each the same initially novel objects or inconsistently with different objects. Our results provide strong evidence that these young infants extract statistic regularities in the distribution of the co‐occurrences of objects and words extremely quickly. The data suggest that this ability is based on the rapid formation of associations between the neural representations of objects and words, but that the new associations are not retained in long‐term memory until the next day. The type of brain response moreover indicates that, unlike in older infants, in 3‐month‐olds a semantic processing stage is not involved. Their ability to combine words with meaningful information is caused by a primary learning mechanism that enables the formation of proto‐words and acts as a precursor for the acquisition of genuine words.     

汉语婴儿词汇学习的注意偏好

婴儿的动、名词词类学习存在跨文化差异,但是很少研究从注意偏好角度解释这类差异。本研究利用习惯化范式考察汉语婴儿在6-8个月和17-19个月时对事件中人物,动作和物体的区分。结果发现,6-8个月的婴儿仅能区分动作变化,对人物和物体无法区分,而17-19个月的婴儿对三类变化均可以区分。本研究提供了婴儿早期注意偏好发展的实验依据,同时为儿童早期单词获得提供了新的理论基础。     

Do 6‐month‐olds understand that speech can communicate?

Adults and 12‐month‐old infants recognize that even unfamiliar speech can communicate information between third parties, suggesting that they can separate the communicative function of speech from its lexical content. But do infants recognize that speech can communicate due to their experience understanding and producing language, or do they appreciate that speech is communicative earlier, with little such experience? We examined whether 6‐month‐olds recognize that speech can communicate information about an object. Infants watched a Communicator selectively grasp one of two objects (target). During test, the Communicator could no longer reach the objects; she turned to a Recipient and produced speech (a nonsense word) or non‐speech (coughing). Infants looked longer when the Recipient selected the non‐target than the target object when the Communicator spoke but not when she coughed – unless the Recipient had previously witnessed the Communicator's selective grasping of the target object. Our results suggest that at 6 months, with a receptive vocabulary of no more than a handful of commonly used words, infants possess some abstract understanding of the communicative function of speech. This understanding may provide an early mechanism for language and knowledge acquisition.     

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.     

The effects of adults' affective expression and direction of visual gaze on 12‐month‐olds' visual preferences for an object following a 5‐minute, 1‐day,or 1‐month delay

Between 12‐ and 14 months of age infants begin to use another's direction of gaze and affective expression in learning about various objects and events. What is not well understood is how long infants' behaviour towards a previously unfamiliar object continues to be influenced following their participation in circumstances of social referencing. In this experiment, we examined infants' sensitivity to an adult's direction of gaze and their visual preference for one of two objects following a 5‐min, 1‐day, or 1‐month delay. Ninety‐six 12‐month‐olds participated. For half of the infants during habituation (i.e., familiarization), the adults' direction of gaze was directed towards an unfamiliar object (look condition). For the remaining half of the infants during habituation, the adults' direction of gaze was directed away from the unfamiliar object (look‐away condition). All infants were habituated to two events. One event consisted of an adult looking towards (look condition) or away from (look‐away condition) an object while facially and vocally conveying a positive affective expression. The second event consisted of the same adult looking towards or away from a different object while conveying a disgusted affective expression. Following the habituation phase and a 5‐min, 1‐day, or 1‐month delay, infants' visual preference was assessed. During the visual preference phase, infants saw the two objects side by side where the adult conveying the affective expression was not visible. Results of the visual preference phase indicate that infants in the look condition showed a significant preference for object previously paired with the positive affect following a 5‐min and 1‐day delay. No significant visual preference was found in the look condition following a 1‐month delay. No significant preferences were found at any retention interval in the look‐away condition. Results are discussed in terms of early learning, social referencing, and early memory.     

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.     

Lexical leverage: category knowledge boosts real‐time novel word recognition in 2‐year‐olds

Recent research suggests that infants tend to add words to their vocabulary that are semantically related to other known words, though it is not clear why this pattern emerges. In this paper, we explore whether infants leverage their existing vocabulary and semantic knowledge when interpreting novel label–object mappings in real time. We initially identified categorical domains for which individual 24‐month‐old infants have relatively higher and lower levels of knowledge, irrespective of overall vocabulary size. Next, we taught infants novel words in these higher and lower knowledge domains and then asked if their subsequent real‐time recognition of these items varied as a function of their category knowledge. While our participants successfully acquired the novel label–object mappings in our task, there were important differences in the way infants recognized these words in real time. Namely, infants showed more robust recognition of high (vs. low) domain knowledge words. These findings suggest that dense semantic structure facilitates early word learning and real‐time novel word recognition.     

Self‐generated variability in object images predicts vocabulary growth

Object names are a major component of early vocabularies and learning object names depends on being able to visually recognize objects in the world. However, the fundamental visual challenge of the moment‐to‐moment variations in object appearances that learners must resolve has received little attention in word learning research. Here we provide the first evidence that image‐level object variability matters and may be the link that connects infant object manipulation to vocabulary development. Using head‐mounted eye tracking, the present study objectively measured individual differences in the moment‐to‐moment variability of visual instances of the same object, from infants’ first‐person views. Infants who generated more variable visual object images through manual object manipulation at 15 months of age experienced greater vocabulary growth over the next six months. Elucidating infants’ everyday visual experiences with objects may constitute a crucial missing link in our understanding of the developmental trajectory of object name learning.     

Looking is not enough: Multimodal attention supports the real-time learning of new words

Most research on early language learning focuses on the objects that infants see and the words they hear in their daily lives, although growing evidence suggests that motor development is also closely tied to language development. To study the real-time behaviors required for learning new words during free-flowing toy play, we measured infants’ visual attention and manual actions on to-be-learned toys. Parents and 12-to-26-month-old infants wore wireless head-mounted eye trackers, allowing them to move freely around a home-like lab environment. After the play session, infants were tested on their knowledge of object-label mappings. We found that how often parents named objects during play did not predict learning, but instead, it was infants’ attention during and around a labeling utterance that predicted whether an object-label mapping was learned. More specifically, we found that infant visual attention alone did not predict word learning. Instead, coordinated, multimodal attention–when infants’ hands and eyes were attending to the same object–predicted word learning. Our results implicate a causal pathway through which infants’ bodily actions play a critical role in early word learning.     

Word frequency as a cue for identifying function words in infancy

While content words (e.g., ‘dog’) tend to carry meaning, function words (e.g., ‘the’) mainly serve syntactic purposes. Here, we ask whether 17-month old infants can use one language–universal cue to identify function word candidates: their high frequency of occurrence. In Experiment 1, infants listened to a series of short, naturally recorded sentences in a foreign language (i.e., in French). In these sentences, two determiners appeared much more frequently than any content word. Following this, infants were presented with a visual object, and simultaneously with a word pair composed of a determiner and a noun. Results showed that infants associated the object more strongly with the infrequent noun than with the frequent determiner. That is, when presented with both the old object and a novel object, infants were more likely to orient towards the old object when hearing a label with a new determiner and the old noun compared to a label with a new noun and the old determiner. In Experiment 2, infants were tested using the same procedure as in Experiment 1, but without the initial exposure to French sentences. Under these conditions, infants did not preferentially associate the object with nouns, suggesting that the preferential association between nouns and objects does not result from specific acoustic or phonological properties. In line with various biases and heuristics involved in acquiring content words, we provide the first direct evidence that infants can use distributional cues, especially the high frequency of occurrence, to identify potential function words.     

Electrophysiological evidence for the understanding of maternal speech by 9-month-old infants

Early word learning in infants relies on statistical, prosodic, and social cues that support speech segmentation and the attachment of meaning to words. It is debated whether such early word knowledge represents mere associations between sound patterns and visual object features, or reflects referential understanding of words. By measuring an event-related brain potential component known as the N400, we demonstrated that 9-month-old infants can detect the mismatch between an object appearing from behind an occluder and a preceding label with which their mother introduces it. Differential N400 amplitudes have been shown to reflect semantic priming in adults, and its absence in infants has been interpreted as a sign of associative word learning. By setting up a live communicative situation for referring to objects, we demonstrated that a similar priming effect also occurs in young infants. This finding may indicate that word meaning is referential from the outset of word learning and that referential expectation drives, rather than results from, vocabulary acquisition in humans.     

Influences of vowel and tone variation on emergent word knowledge: a cross‐linguistic investigation

To learn words, infants must be sensitive to native phonological contrast. While lexical tone predominates as a source of phonemic contrast in human languages, there has been little investigation of the influences of lexical tone on word learning. The present study investigates infants’ sensitivity to tone mispronunciations in two groups of infants. For one group (Chinese learners), tone is phonemic in their native language, and for the second group (English learners), tone is non‐phonemic and constituted suprasegmental variation. In Experiment 1, English learners were trained on novel word–object pairings and tested on their recognition of correct pronunciations, tone and vowel mispronunciations of these words at 18 and 24 months. In Experiment 2a, bilingual English‐Chinese learners were tested on a similar task translated into Chinese at the same age intervals. Results demonstrate that non‐tonal learners treated tonal and vowel substitutions alike as mispronunciations at 18 months but only treated vowel substitutions as mispronunciations at 24 months. Tonal learners treated both tonal and vowel substitutions as mispronunciations at both ages. In Experiment 2b, bilingual non‐tone language learners were tested on the same set of tasks replicating a similar set of results as monolingual non‐tone language learners (Experiment 1). Findings point to an early predisposition to treat tone as a defining characteristic of words regardless of its lexical relevance at 18 months. Between 18 and 24 months, learners appear to ascribe lexical relevance to tone in a language‐specific manner. The current study identifies the influences of tone variation on memories for newly learned words and the time period during which lexical tone – a highly frequent constituent of human languages – actually becomes lexical for early learners. Findings are contextualized with prevailing models of the developing lexicon.     

Mapping novel labels to actions: how the rhythm of words guides infants' learning

We investigated the effect of lexical stress on 16-month-olds' ability to form associations between labels and paths of motion. Disyllabic English nouns tend to have a strong-weak (trochaic) stress pattern, and verbs tend to have a weak-strong (iambic) pattern. We explored whether infants would use word stress information to guide word-action associations during learning. Infants heard two novel words with either verb-like iambic stress or noun-like trochaic stress. Each word was paired with a single novel object performing one of two path actions and was tested using path-switch trials. Only infants in the iambic stress condition learned the association between the novel words and the path actions. To further investigate infants' difficulty in mapping the trochaic labels to the actions, we conducted an additional study in which infants were given an object switch task using the trochaic labels. In this case, infants were able to associate the trochaic labels with the objects, providing further support that infants use lexical stress to guide label-referent associations. This study demonstrates that by 16months, English-learning infants have developed a bias to expect disyllabic action labels to have iambic stress patterns, consistent with native language stress patterns.     

The intersensory origins of word‐comprehension: an ecological–dynamic systems view

How do infants begin to understand spoken words? Recent research suggests that word comprehension develops from the early detection of intersensory relations between conventionally paired auditory speech patterns (words) and visible objects or actions. More importantly, in keeping with dynamic systems principles, the findings suggest that word comprehension develops from a dynamic and complementary relationship between the organism (the infant) and the environment (language addressed to the infant). In addition, parallel findings from speech and non‐speech studies of intersensory perception provide evidence for domain general processes in the development of word comprehension. These research findings contrast with the view that a lexical acquisition device with specific lexical principles and innate constraints is required for early word comprehension. Furthermore, they suggest that learning of word–object relations is not merely an associative process. The data support an alternative view of the developmental process that emphasizes the dynamic and reciprocal interactions between general intersensory perception, selective attention and learning in infants, and the specific characteristics of maternal communication.     

Social interaction facilitates word learning in preverbal infants: Word–object mapping and word segmentation

In natural settings, infants learn spoken language with the aid of a caregiver who explicitly provides social signals. Although previous studies have demonstrated that young infants are sensitive to these signals that facilitate language development, the impact of real-life interactions on early word segmentation and word–object mapping remains elusive. We tested whether infants aged 5–6 months and 9–10 months could segment a word from continuous speech and acquire a word–object relation in an ecologically valid setting. In Experiment 1, infants were exposed to a live tutor, while in Experiment 2, another group of infants were exposed to a televised tutor. Results indicate that both younger and older infants were capable of segmenting a word and learning a word–object association only when the stimuli were derived from a live tutor in a natural manner, suggesting that real-life interaction enhances the learning of spoken words in preverbal infants.     

Learning about sounds contributes to learning about words: Effects of prosody and phonotactics on infant word learning

This research investigates how early learning about native language sound structure affects how infants associate sounds with meanings during word learning. Infants (19-month-olds) were presented with bisyllabic labels with high or low phonotactic probability (i.e., sequences of frequent or infrequent phonemes in English). The labels were produced with the predominant English trochaic (strong/weak) stress pattern or the less common iambic (weak/strong) pattern. Using the habituation-based Switch Task to test label learning, we found that infants readily learned high probability trochaic labels. However, they failed to learn low probability labels, regardless of stress, and failed to learn iambic labels, regardless of phonotactics. Thus, infants required support from both common phoneme sequences and a common stress pattern to map the labels to objects. These findings demonstrate that early word learning is shaped by prior knowledge of native language phonological regularities and provide support for the role of statistical learning in language acquisition.