The Origins of Verb Learning: Preverbal and Postverbal Infants' Learning of Word-Action Relations

Face-to-face contact during infancy: How the development of gaze to faces feeds into infants' vocabulary outcomes

Infants acquire their first words through interactions with social partners. In the first year of life, infants receive a high frequency of visual and auditory input from faces, making faces a potential strong social cue in facilitating word-to-world mappings. In this position paper, we review how and when infant gaze to faces is likely to support their subsequent vocabulary outcomes. We assess the relevance of infant gaze to faces selectively, in three domains: infant gaze to different features within a face (that is, eyes and mouth); then to faces (compared to objects); and finally to more socially relevant types of faces. We argue that infant gaze to faces could scaffold vocabulary construction, but its relevance may be impacted by the developmental level of the infant and the type of task with which they are presented. Gaze to faces proves relevant to vocabulary, as gazes to eyes could inform about the communicative nature of the situation or about the labeled object, while gazes to the mouth could improve word processing, all of which are key cues to highlighting word-to-world pairings. We also discover gaps in the literature regarding how infants' gazes to faces (versus objects) or to different types of faces relate to vocabulary outcomes. An important direction for future research will be to fill these gaps to better understand the social factors that influence infant vocabulary outcomes.

When "shoe" becomes free from "putting on": The link between early meanings of object words and object-specific actions

Nouns referring to objects dominate children's early vocabulary over verbs referring to actions. However, some scholars have argued that early object-word meanings cannot be easily classified into specific object categories; rather, they have much undifferentiated meanings in which both objects and their specific actions are intertwined. We experimentally investigated this view using a two-alternative forced-choice task involving toddlers aged 18-23 months (n = 69). Both the cross-sectional and longitudinal results suggested that unlike older toddlers, younger ones could not select the correct referents when objects and object-specific actions were presented separately (e.g., "doing a filler action with shoes" vs. "putting on filler objects as if they were shoes") despite being successful when both were matched (e.g., "putting shoes on" vs. "doing a filler action with filler objects"). Additionally, toddlers failed to judge object-word referents solely by object-specific actions. These results indicated that early object-word meanings constitute the undifferentiated fusion of both objects and actions, and they subsequently differentiate into specific object categories independent of actions. Furthermore, the extent of such semantic differentiation is associated with the vocabulary growth of action words, suggesting that object-word meaning differentiation encouraged toddlers to develop new labels that could distinguish specific actions from objects. These findings revealed the uniqueness of young children's object-word comprehension, which is different from that of adults.

Motion tracking of parents' infant- versus adult-directed actions reveals general and action-specific modulations

Parents tend to modulate their movements when demonstrating actions to their infants. Thus far, these modulations have primarily been quantified by human raters and for entire interactions, thereby possibly overlooking the intricacy of such demonstrations. Using optical motion tracking, the precise modulations of parents' infant-directed actions were quantified and compared to adult-directed actions and between action types. Parents demonstrated four novel objects to their 14-month-old infants and adult confederates. Each object required a specific action to produce a unique effect (e.g. rattling). Parents were asked to demonstrate an object at least once before passing it to their demonstration partner, and they were subsequently free to exchange the object as often as desired. Infants' success at producing the objects' action-effects was coded during the demonstration session and their memory of the action-effects was tested after a several-minute delay. Indicating general modulations across actions, parents repeated demonstrations more often, performed the actions in closer proximity and demonstrated action-effects for longer when interacting with their infant compared to the adults. Meanwhile, modulations of movement size and velocity were specific to certain action-effect pairs. Furthermore, a 'just right' modulation of proximity was detected, since infants' learning, memory, and parents' prior evaluations of their infants' motor abilities, were related to demonstrations that were performed neither too far from nor too close to the infants. Together, these findings indicate that infant-directed action modulations are not solely overall exaggerations but are dependent upon the characteristics of the to-be learned actions, their effects, and the infant learners.

Young Mandarin learners use function words to distinguish between nouns and verbs

Mandarin requires neither determiners nor morphological inflections, which casts doubt on Mandarin-speaking children's ability to use function words as a syntactic bootstrapping tool to identify the form class of a new word. This study examined 3- and 5-year-old Mandarin learners' ability to use function words to interpret new words as either nouns or verbs in the absence of the requirement for determiners and inflections in the ambient language. In Experiment 1, 3-, and 5-year-old Mandarin-speaking children were exposed to eight novel words embedded in sentence frames differing only in the form class markers used. The 5-year-olds interpreted the novel words as either nouns or verbs depending on the form class markers they heard, while the 3-year-olds learned only the nouns. Experiment 2 confirmed that the 5-year-olds understood the function of the verb-marker. Thus, Mandarin-speaking children can use function words to distinguish nouns versus verbs, and this ability appears between three and five years of age.

Stacking the evidence: Parents' use of acoustic packaging with preschoolers

Segmenting continuous events into discrete actions is critical for understanding the world. As infants may lack top-down knowledge of event structure, caregivers provide audiovisual cues to guide the process, aligning action descriptions with event boundaries to increase their salience. This acoustic packaging may be specific to infant-directed speech, but little is known about when and why the use of this cue wanes. We explore whether acoustic packaging persists in parents' teaching of 2.5-5.5-year-old children about various toys. Parents produced a smaller percentage of action speech relative to studies with infants. However, action speech largely remained more aligned to action boundaries relative to non-action speech. Further, for the more challenging novel toys, parents modulated their use of acoustic packaging, providing it more for those children with lower vocabularies. Our findings suggest that acoustic packaging persists beyond interactions with infants, underscoring the utility of multimodal cues for learning, particularly for less knowledgeable learners in challenging learning environments.

Word-object and action-object association learning across early development

Successful communication often involves comprehension of both spoken language and observed actions with and without objects. Even very young infants can learn associations between actions and objects as well as between words and objects. However, in daily life, children are usually confronted with both kinds of input simultaneously. Choosing the critical information to attend to in such situations might help children structure the input, and thereby, allow for successful learning. In the current study, we therefore, investigated the developmental time course of children's and adults' word and action learning when given the opportunity to learn both word-object and action-object associations for the same object. All participants went through a learning phase and a test phase. In the learning phase, they were presented with two novel objects which were associated with a distinct novel name (e.g., "Look, a Tanu") and a distinct novel action (e.g., moving up and down while tilting sideways). In the test phase, participants were presented with both objects on screen in a baseline phase, then either heard one of the two labels or saw one of the two actions in a prime phase, and then saw the two objects again on screen in a recognition phase. Throughout the trial, participants' target looking was recorded to investigate whether participants looked at the target object upon hearing its label or seeing its action, and thus, would show learning of the word-object and action-object associations. Growth curve analyses revealed that 12-month-olds showed modest learning of action-object associations, 36-month-olds learned word-object associations, and adults learned word-object and action-object associations. These results highlight how children attend to the different information types from the two modalities through which communication is addressed to them. Over time, with increased exposure to systematic word-object mappings, children attend less to action-object mappings, with the latter potentially being mediated by word-object learning even in adulthood. Thus, choosing between different kinds of input that may be more relevant in their rich environment encompassing different modalities might help learning at different points in development.

The Use of Pitch Accent in Word-Object Association by Monolingual Japanese Infants

This study investigated the lexical use of Japanese pitch accent in Japanese-learning infants. A word-object association task revealed that 18-month-old infants succeeded in learning the associations between two nonsense objects paired with two nonsense words minimally distinguished by pitch pattern (Experiment 1). In contrast, 14-month-old infants failed (Experiment 2). Eighteen-month-old infants succeeded even for sounds that contained only the prosodic information (Experiment 3). However, a subsequent experiment revealed that 14-month-old infants succeeded in an easier single word-object task using pitch contrast (Experiment 4). These findings indicate that pitch pattern information is robustly available to 18-month-old Japanese monolingual infants in a minimal pair word-learning situation, but only partially accessible in the same context for 14-month-old infants.