Developmental Change in Infants' Detection of Visual Faces that Match Auditory Vowels

Early recognition of familiar word-forms as a function of production skills

Growing evidence shows that early speech processing relies on information extracted from speech production. In particular, production skills are linked to word-form processing, as more advanced producers prefer listening to pseudowords containing consonants they do not yet produce. However, it is unclear whether production affects word-form encoding (the translation of perceived phonological information into a memory trace) and/or recognition (the automatic retrieval of a stored item). Distinguishing recognition from encoding makes it possible to explore whether sensorimotor information is stored in long-term phonological representations (and thus, retrieved during recognition) or is processed when encoding a new item, but not necessarily when retrieving a stored item. In this study, we asked whether speech-related sensorimotor information is retained in long-term representations of word-forms. To this aim, we tested the effect of production on the recognition of ecologically learned, real familiar word-forms. Testing these items allowed to assess the effect of sensorimotor information in a context in which encoding did not happen during testing itself. Two groups of French-learning monolinguals (11- and 14-month-olds) participated in the study. Using the Headturn Preference Procedure, each group heard two lists, each containing 10 familiar word-forms composed of either early-learned consonants (commonly produced by French-learners at these ages) or late-learned consonants (more rarely produced at these ages). We hypothesized differences in listening preferences as a function of word-list and/or production skills. At both 11 and 14 months, babbling skills modulated orientation times to the word-lists containing late-learned consonants. This specific effect establishes that speech production impacts familiar word-form recognition by 11 months, suggesting that sensorimotor information is retained in long-term word-form representations and accessed during word-form processing.

Face Processing in Early Development: A Systematic Review of Behavioral Studies and Considerations in Times of COVID-19 Pandemic

Human faces are one of the most prominent stimuli in the visual environment of young infants and convey critical information for the development of social cognition. During the COVID-19 pandemic, mask wearing has become a common practice outside the home environment. With masks covering nose and mouth regions, the facial cues available to the infant are impoverished. The impact of these changes on development is unknown but is critical to debates around mask mandates in early childhood settings. As infants grow, they increasingly interact with a broader range of familiar and unfamiliar people outside the home; in these settings, mask wearing could possibly influence social development. In order to generate hypotheses about the effects of mask wearing on infant social development, in the present work, we systematically review N = 129 studies selected based on the most recent PRISMA guidelines providing a state-of-the-art framework of behavioral studies investigating face processing in early infancy. We focused on identifying sensitive periods during which being exposed to specific facial features or to the entire face configuration has been found to be important for the development of perceptive and socio-communicative skills. For perceptive skills, infants gradually learn to analyze the eyes or the gaze direction within the context of the entire face configuration. This contributes to identity recognition as well as emotional expression discrimination. For socio-communicative skills, direct gaze and emotional facial expressions are crucial for attention engagement while eye-gaze cuing is important for joint attention. Moreover, attention to the mouth is particularly relevant for speech learning. We discuss possible implications of the exposure to masked faces for developmental needs and functions. Providing groundwork for further research, we encourage the investigation of the consequences of mask wearing for infants' perceptive and socio-communicative development, suggesting new directions within the research field.

A Bayesian meta-analysis of infants' ability to perceive audio-visual congruence for speech

This paper quantifies the extent to which infants can perceive audio-visual congruence for speech information and assesses whether this ability changes with native language exposure over time. A hierarchical Bayesian robust regression model of 92 separate effect sizes extracted from 24 studies indicates a moderate effect size in a positive direction (0.35, CI [0.21: 0.50]). This result suggests that infants possess a robust ability to detect audio-visual congruence for speech. Moderator analyses, moreover, suggest that infants' audio-visual matching ability for speech emerges at an early point in the process of language acquisition and remains stable for both native and non-native speech throughout early development. A sensitivity analysis of the meta-analytic data, however, indicates that a moderate publication bias for significant results could shift the lower credible interval to include null effects. Based on these findings, we outline recommendations for new lines of enquiry and suggest ways to improve the replicability of results in future investigations.

Bridging ears and eyes when learning spoken words: On the effects of bilingual experience at 30 months

From the very first moments of their lives, infants selectively attend to the visible orofacial movements of their social partners and apply their exquisite speech perception skills to the service of lexical learning. Here we explore how early bilingual experience modulates children's ability to use visible speech as they form new lexical representations. Using a cross-modal word-learning task, bilingual children aged 30 months were tested on their ability to learn new lexical mappings in either the auditory or the visual modality. Lexical recognition was assessed either in the same modality as the one used at learning ('same modality' condition: auditory test after auditory learning, visual test after visual learning) or in the other modality ('cross-modality' condition: visual test after auditory learning, auditory test after visual learning). The results revealed that like their monolingual peers, bilingual children successfully learn new words in either the auditory or the visual modality and show cross-modal recognition of words following auditory learning. Interestingly, as opposed to monolinguals, they also demonstrate cross-modal recognition of words upon visual learning. Collectively, these findings indicate a bilingual edge in visual word learning, expressed in the capacity to form a recoverable cross-modal representation of visually learned words.

Sensorimotor influences on speech perception in pre-babbling infants: Replication and extension of Bruderer et al. (2015)

The relationship between speech perception and production is central to understanding language processing, yet remains under debate, particularly in early development. Recent research suggests that in infants aged 6 months, when the native phonological system is still being established, sensorimotor information from the articulators influences speech perception: The placement of a teething toy restricting tongue-tip movements interfered with infants' discrimination of a non-native contrast, /Da/-/da/, that involves tongue-tip movement. This effect was selective: A different teething toy that prevented lip closure but not tongue-tip movement did not disrupt discrimination. We conducted two sets of studies to replicate and extend these findings. Experiments 1 and 2 replicated the study by Bruderer et al. (Proceedings of the National Academy of Sciences of the United States of America, 112 (44), 13531-13536, 2015), but with synthesized auditory stimuli. Infants discriminated the non-native contrast (dental /da/ - retroflex /Da/) (Experiment 1), but showed no evidence of discrimination when the tongue-tip movement was prevented with a teething toy (Experiment 2). Experiments 3 and 4 extended this work to a native phonetic contrast (bilabial /ba/ - dental /da/). Infants discriminated the distinction with no teething toy present (Experiment 3), but when they were given a teething toy that interfered only with lip closure, a movement involved in the production of /ba/, discrimination was disrupted (Experiment 4). Importantly, this was the same teething toy that did not interfere with discrimination of /da/-/Da/ in Bruderer et al. (2015). These findings reveal specificity in the relation between sensorimotor and perceptual processes in pre-babbling infants, and show generalizability to a second phonetic contrast.

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.

The Development of Attentional Biases for Faces in Infancy: A Developmental Systems Perspective

We present an integrative review of research and theory on major factors involved in the early development of attentional biases to faces. Research utilizing behavioral, eye-tracking, and neuroscience measures with infant participants as well as comparative research with animal subjects are reviewed. We begin with coverage of research demonstrating the presence of an attentional bias for faces shortly after birth, such as newborn infants' visual preference for face-like over non-face stimuli. The role of experience and the process of perceptual narrowing in face processing are examined as infants begin to demonstrate enhanced behavioral and neural responsiveness to mother over stranger, female over male, own- over other-race, and native over non-native faces. Next, we cover research on developmental change in infants' neural responsiveness to faces in multimodal contexts, such as audiovisual speech. We also explore the potential influence of arousal and attention on early perceptual preferences for faces. Lastly, the potential influence of the development of attention systems in the brain on social-cognitive processing is discussed. In conclusion, we interpret the findings under the framework of Developmental Systems Theory, emphasizing the combined and distributed influence of several factors, both internal (e.g., arousal, neural development) and external (e.g., early social experience) to the developing child, in the emergence of attentional biases that lead to enhanced responsiveness and processing of faces commonly encountered in the native environment.

Learning Spoken Words via the Ears and Eyes: Evidence from 30-Month-Old Children

From the very first moments of their lives, infants are able to link specific movements of the visual articulators to auditory speech signals. However, recent evidence indicates that infants focus primarily on auditory speech signals when learning new words. Here, we ask whether 30-month-old children are able to learn new words based solely on visible speech information, and whether information from both auditory and visual modalities is available after learning in only one modality. To test this, children were taught new lexical mappings. One group of children experienced the words in the auditory modality (i.e., acoustic form of the word with no accompanying face). Another group experienced the words in the visual modality (seeing a silent talking face). Lexical recognition was tested in either the learning modality or in the other modality. Results revealed successful word learning in either modality. Results further showed cross-modal recognition following an auditory-only, but not a visual-only, experience of the words. Together, these findings suggest that visible speech becomes increasingly informative for the purpose of lexical learning, but that an auditory-only experience evokes a cross-modal representation of the words.

The Role of Auditory and Visual Speech in Word Learning at 18 Months and in Adulthood

Visual information influences speech perception in both infants and adults. It is still unknown whether lexical representations are multisensory. To address this question, we exposed 18-month-old infants (n = 32) and adults (n = 32) to new word-object pairings: Participants either heard the acoustic form of the words or saw the talking face in silence. They were then tested on recognition in the same or the other modality. Both 18-month-old infants and adults learned the lexical mappings when the words were presented auditorily and recognized the mapping at test when the word was presented in either modality, but only adults learned new words in a visual-only presentation. These results suggest developmental changes in the sensory format of lexical representations.