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1. Social motivation predicts gaze following between 6 and 14 months

   https://doi.org/10.1111/infa.12544  

   Zeng, Guangyu; Leung, Tiffany S.; Maylott, Sarah E.; Saunders, Thea A.; Messinger, Daniel S.; Llabre, Maria M.; Simpson, Elizabeth A. (May 2023, Infancy)

   Abstract Infants vary in their ability to follow others’ gazes, but it is unclear how these individual differences emerge. We tested whether social motivation levels in early infancy predict later gaze following skills. We longitudinally tracked infants’ (N = 82) gazes and pupil dilation while they observed videos of a woman looking into the camera simulating eye contact (i.e., mutual gaze) and then gazing toward one of two objects, at 2, 4, 6, 8, and 14 months of age. To improve measurement validity, we used confirmatory factor analysis to combine multiple observed measures to index the underlying constructs of social motivation and gaze following. Infants’ social motivation—indexed by their speed of social orienting, duration of mutual gaze, and degree of pupil dilation during mutual gaze—was developmentally stable and positively predicted the development of gaze following—indexed by their proportion of time looking to the target object, first object look difference scores, and first face‐to‐object saccade difference scores—from 6 to 14 months of age. These findings suggest that infants’ social motivation likely plays a role in the development of gaze following and highlight the use of a multi‐measure approach to improve measurement sensitivity and validity in infancy research. 

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2. Developmental change in English‐learning children's interpretations of salient pitch contours in word learning

   https://doi.org/10.1111/infa.12587  

   Quam, Carolyn; Swingley, Daniel (February 2024, Infancy)

   Abstract To efficiently recognize words, children learning an intonational language like English should avoid interpreting pitch‐contour variation as signaling lexical contrast, despite the relevance of pitch at other levels of structure. Thus far, the developmental time‐course with which English‐learning children rule out pitch as a contrastive feature has been incompletely characterized. Prior studies have tested diverse lexical contrasts and have not tested beyond 30 months. To specify the developmental trajectory over a broader age range, we extended a prior study (Quam & Swingley, 2010), in which 30‐month‐olds and adults disregarded pitch changes, but attended to vowel changes, in newly learned words. Using the same phonological contrasts, we tested 3‐ to 5‐year‐olds, 24‐month‐olds, and 18‐month‐olds. The older two groups were tested using the language‐guided‐looking method. The oldest group attended to vowels but not pitch. Surprisingly, 24‐month‐olds ignored not just pitch but sometimes vowels as well—conflicting with prior findings of phonological constraint at 24 months. The youngest group was tested using the Switch habituation method, half with additional phonetic variability in training. Eighteen‐month‐olds learned both pitch‐contrasted and vowel‐contrasted words, whether or not additional variability was present. Thus, native‐language phonological constraint was not evidenced prior to 30 months (Quam & Swingley, 2010). We contextualize our findings within other recent work in this area. 

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3. The Comprehension Boost in Early Word Learning: Older Infants Are Better Learners: Comprehension Boost in Early Word Learning

   https://doi.org/10.1111/cdep.12373  

   Bergelson, Elika (January 2020, Child Development Perspectives)

   ABSTRACT—Recent research has revealed that infants begin understanding words at around 6 months. After that, infants’ comprehension vocabulary increases grad- ually in a linear way over 8–18 months, according to data from parental checklists. In contrast, infants’ word comprehension improves robustly, qualitatively, and in a nonlinear way just after their first birthday, according to data from studies on spoken word comprehension. In this review, I integrate observational and experimental data to explain these divergent results. I argue that infants’ comprehension boost is not well-explained by changes in their language input for common words, but rather by proposing that they learn to take better advantage of rel- atively stable input data. Next, I propose potentially complementary theoretical accounts of what makes older infants better learners. Finally, I suggest how the research community can expand our empirical base in this understudied area, and why doing so will inform our knowledge about child development. 

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4. The role of vision in the acquisition of words: Vocabulary development in blind toddlers

   https://doi.org/10.1111/desc.13475  

   Campbell, Erin; Casillas, Robyn; Bergelson, Elika (January 2024, Developmental Science)

   Abstract What is vision's role in driving early word production? To answer this, we assessed parent‐report vocabulary questionnaires administered to congenitally blind children (N = 40, Mean age = 24 months [R: 7–57 months]) and compared the size and contents of their productive vocabulary to those of a large normative sample of sighted children (N = 6574). We found that on average, blind children showed a roughly half‐year vocabulary delay relative to sighted children, amid considerable variability. However, the content of blind and sighted children's vocabulary was statistically indistinguishable in word length, part of speech, semantic category, concreteness, interactiveness, and perceptual modality. At a finer‐grained level, we also found that words’ perceptual properties intersect with children's perceptual abilities. Our findings suggest that while an absence of visual input may initially make vocabulary development more difficult, the content of the early productive vocabulary is largely resilient to differences in perceptual access. Research HighlightsInfants and toddlers born blind (with no other diagnoses) show a 7.5 month productive vocabulary delay on average, with wide variability.Across the studied age range (7–57 months), vocabulary delays widened with age.Blind and sighted children's early vocabularies contain similar distributions of word lengths, parts of speech, semantic categories, and perceptual modalities.Blind children (but not sighted children) were more likely to say visual words which could also be experienced through other senses. 

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5. Social Inference May Guide Early Lexical Learning

   https://doi.org/10.3389/fpsyg.2021.645247  

   Tripp, Alayo; Feldman, Naomi H.; Idsardi, William J. (May 2021, Frontiers in Psychology)

   null (Ed.)

   We incorporate social reasoning about groups of informants into a model of word learning, and show that the model accounts for infant looking behavior in tasks of both word learning and recognition. Simulation 1 models an experiment where 16-month-old infants saw familiar objects labeled either correctly or incorrectly, by either adults or audio talkers. Simulation 2 reinterprets puzzling data from the Switch task, an audiovisual habituation procedure wherein infants are tested on familiarized associations between novel objects and labels. Eight-month-olds outperform 14-month-olds on the Switch task when required to distinguish labels that are minimal pairs (e.g., “buk” and “puk”), but 14-month-olds' performance is improved by habituation stimuli featuring multiple talkers. Our modeling results support the hypothesis that beliefs about knowledgeability and group membership guide infant looking behavior in both tasks. These results show that social and linguistic development interact in non-trivial ways, and that social categorization findings in developmental psychology could have substantial implications for understanding linguistic development in realistic settings where talkers vary according to observable features correlated with social groupings, including linguistic, ethnic, and gendered groups. 

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