Implications of social competence among thirty-month-old toddlers: a theory of mind perspective.

BACKGROUND: The purpose of this study was to examine the relations between children's social competence and initial index of theory of mind at 30 months of age. METHODS: The participants of the study were 322 toddlers and parents/caregivers who were registered with the Japan Science and Technology Agency (JST) project. They completed a five-minute interaction session, which was coded using the Interaction Rating Scale (IRS) as an evidence-based practical index of children's social competence. In addition, the children were asked to complete a diverse-desire task as a ToM (theory of mind) index. RESULTS: The results showed that the ToM index was related to the total score and subscales of the IRS, such as Empathy and Emotional regulation. CONCLUSIONS: These findings show that the IRS score was related to ToM task performance at 30 months of age.

Does the conceptual distinction between singular and plural sets depend on language?

Previous studies indicate that English-learning children acquire the distinction between singular and plural nouns between 22 and 24 months of age. Also, their use of the distinction is correlated with the capacity to distinguish nonlinguistically between singular and plural sets in a manual search paradigm (D. Barner, D. Thalwitz, J. Wood, S. Yang, & S. Carey, 2007). The authors used 3 experiments to explore the causal relation between these 2 capacities. Relative to English, Japanese and Mandarin had impoverished singular-plural marking. Using the manual search task, in Experiment 1 the authors found that by around 22 months of age, Japanese children also distinguished between singular and plural sets. Experiments 2 and 3 extended this finding to Mandarin-learning toddlers. Mandarin learners who were 20-24 months of age did not yet comprehend Mandarin singular-plural marking (i.e., yige vs. yixie, or -men), yet they did distinguish between singular and plural sets in manual search. These experiments suggest that knowledge of singular-plural morphology is not necessary for deploying the nonlinguistic distinction between singular and plural sets.

Contribution of parenting factors to the developmental attainment of 9-month-old infants: results from the Japan Children's Study.

BACKGROUND: Child development integrates several interdependent domains, but few studies have attempted to identify the common factors that contribute to these different domains of development in infancy. The aim of the present study was to identify the factors that contribute to several domains of developmental attainment in 9-month-old infants. METHODS: We used data from the Japan Children's Study, a prospective cohort study underway in Japan since 2005. Mothers completed questionnaires about their children's temperament, coparenting behaviors, maternal parenting stress, and parenting behavior. The Kinder infant development scale was used to evaluate child development outcomes. RESULTS: A total of 270 children were included in this analysis. After adjusting for the children's birth weight, gestational age, temperament, and other family environmental variables, multiple logistic regression analyses showed that greater maternal cognitive stimulation was associated with the development of receptive language, expressive language, social relationships, and feeding. Results also suggest that early supportive coparenting helped to promote development in manipulation, receptive language, and social relationships. Maternal parenting stress was stable between the infant ages of 4 and 9 months and was negatively correlated with scores for coparenting and maternal stimulation, which suggests an indirect effect of maternal parenting stress on child outcomes. CONCLUSIONS: Supportive coparenting and maternal cognitive stimulation were the most important contributors to most domains of child development. Our findings suggest that educational interventions targeting young families would help parents establish and maintain an environment of successful coparenting and cognitive stimulation as their children grow.

Individual differences in changes in infants' interest in social signals in relation to developmental index.

Detection of social signals, such as biological motion and social causality, is of basic importance in early infancy. There have also been some accounts that infants' visual preference or reaction to social signals change during development because of their changing understanding of such signals, and the detective abilities of primary social signals are related to later social development. In this study, we attempted to find different developmental patterns in individuals in terms of their visual preference for biological motion and socially causal movements at 4, 9, and 18 months and 4 and 9 months, respectively, using a cluster analysis. It was found that for both types of social signals, the infants who demonstrated an increased interest in social stimuli at 9 months scored higher on the developmental index than those who showed a decrease, suggesting a difference in the quality of understanding of social signals at 9 months.

Development of infants' request expressions from 11 to 15 months.

Between 10 and 15 months of age, infants seem to become increasingly communicative. The focus of this study was changes in request behavior among infants at ages 11, 13, and 15 months (N = 22) in a longitudinal design. Changes in durations and frequencies of four different modes of behavior were examined, namely, use of hands, eye gaze, facial expression, and vocalization. Both frequencies and durations of the behaviors expressing requests increased with age, while those of nonrequest behaviors showed a different trend. Also investigated were changes in temporal coordination of different request modes. A greater number of infants used greater combinations of co-occurring modes when they were older than when they were younger.

[Infants' responses to the still-face situation at five and nine months: focusing on sex differences].

This study investigated developmental changes and sex differences in infants' responses to a female stranger during a face-to-face interaction, still-face, and reunion phase. Twenty-two infants (11 boys and 11 girls) were observed at five and nine months of age. At five months, the infants smiled less in the still-face phase, while at nine months the infants smiled less at each subsequent phase. Girls, but not boys, smiled more at nine months than five months. Girls' gazing toward the social partner's face decreased during the still-face and reunion phases. Girls gazed toward the social partner's face more than the boys, independent of the phases and age. The findings support the view the effect of a still-face on infants is robust at both five and nine months and for both sexes. But the effect remained in the reunion phase only for the nine-month-olds. These findings suggest that girls have more interest in their social partner than boys.

From grammatical number to exact numbers: early meanings of 'one', 'two', and 'three' in English, Russian, and Japanese.

This study examined whether singular/plural marking in a language helps children learn the meanings of the words 'one,' 'two,' and 'three.' First, CHILDES data in English, Russian (which marks singular/plural), and Japanese (which does not) were compared for frequency, variability, and contexts of number-word use. Then young children in the USA, Russia, and Japan were tested on Counting and Give-N tasks. More English and Russian learners knew the meaning of each number word than Japanese learners, regardless of whether singular/plural cues appeared in the task itself (e.g., "Give two apples" vs. "Give two"). These results suggest that the learning of "one," "two" and "three" is supported by the conceptual framework of grammatical number, rather than that of integers.

The use of nouns and verbs by Japanese children and their caregivers in book-reading and toy-playing contexts.

Japanese provides a valuable contrast for crosslinguistic studies of noun and verb dominance in early child language, and the effect of input on the early lexicon. In this study, 31 Japanese children between 1;0 and 2;0 and their caregivers were recorded in two contexts: joint bookreading and play with toys. Context had the largest effect, as nouns were much more frequent in the book context. Noun dominance was constant across development in the book context, but in the toy context there was a shift away as children developed from single words through the presyntactic stage to the syntactic stage. Caregiver language was verb dominant in a number of respects across development in the toy context, and thus was not closely related to child lexical balance. We conclude that in early lexical development, all children have a conceptual disposition to learn nouns. With vocabulary growth and the emergence of grammar, the proportion of verbs increases substantially, and at this stage properties of the input language may influence development.