Published papers

Children's foreign-language (FL) learning is a matter of much social as well as scientific debate. Previous behavioral research indicates that starting language learning late in life can lead to problems in phonological processing. Inadequate phonological capacity may impede lexical learning and semantic processing (phonological bottleneck hypothesis). Using both behavioral and neuroimaging data, here we examine the effects of age of first exposure (AOFE) and total hours of exposure (HOE) to English, on 350 Japanese primary-school children's semantic processing of spoken English. Children's English proficiency scores and N400 event-related brain potentials (ERPs) were analyzed in multiple regression analyses. The results showed (1) that later, rather than earlier, AOFE led to higher English proficiency and larger N400 amplitudes, when HOE was controlled for; and (2) that longer HOE led to higher English proficiency and larger N400 amplitudes, whether AOFE was controlled for or not. These data highlight the important role of amount of exposure in FL learning, and cast doubt on the view that starting FL learning earlier always produces better results. © 2011 Elsevier Ireland Ltd and the Japan Neuroscience Society.

Is an individual who is sensitive to the facial expressions of a given emotion also sensitive to those of other emotions? This study addressed this simple but fundamental question by examining the latent structure underlying the sensitivity scores for basic emotions expressed by faces (Suzuki, Hoshino, & Shigemasu, 2006a). Eight hundred and five participants took part in the study, and for each participant, the sensitivity scores for happiness, fear, anger, disgust, and sadness were calculated. Variants of a single- factor model were fit to the matrix of correlations among the five sensitivity scores. A solution for the best-fit model indicated an equal contribution from the single factor to the four negative emotions (path coefficient = 0.635) and a smaller contribution to happiness (0.183). Our results imply minimally over- lapped mechanisms underlying the recognition of positive and negative emotions. © 2009 Elsevier Ltd.

In Item Response Theory (IRT), item characteristic curves (ICCs) are illustrated through logistic models or normal ogive models, and the probability that examinees give the correct answer is usually a monotonically increasing function of their ability parameters. However, since only limited patterns of shapes can be obtained from logistic models or normal ogive models, there is a possibility that the model applied does not fit the data. As a result, the existing method can be rejected because it cannot deal with various item response patterns. To overcome these problems, we propose a new semiparametric IRT model using a Dirichlet process mixture logistic distribution. Our method does not rely on assumptions but only requires that the ICCs be a monotonically nondecreasing function; that is, our method can deal with more types of item response patterns than the existing methods, such as the one-parameter normal ogive models or the two- or three-parameter logistic models. We conducted two simulation studies whose results indicate that the proposed method can express more patterns of shapes for ICCs and can estimate the ability parameters more accurately than the existing parametric and nonparametric methods. The proposed method has also been applied to Facial Expression Recognition data with noteworthy results. © 2009 The Psychometric Society.

This study proposes a new item parameter linking method for the common-item nonequivalent groups design in item response theory (IRT). Previous studies assumed that examinees are randomly assigned to either test form. However, examinees can frequently select their own test forms and tests often differ according to examinees' abilities. In such cases, concurrent calibration or multiple group IRT modeling without modeling test form selection behavior can yield severely biased results. We proposed a model wherein test form selection behavior depends on test scores and used a Monte Carlo expectation maximization (MCEM) algorithm. This method provided adequate estimates of testing parameters. © 2008 The Psychometric Society.

The authors propose a concise formula to evaluate the standard error of the estimated latent variable score when the true values of the structural parameters are not known and must be estimated. The formula can be applied to factor scores in factor analysis or ability parameters in item response theory, without bootstrap or Markov chain Monte Carlo methods. The proposed method is valid when both the number of items and the number of subjects are large. However, simulation results suggest that the proposed method provides valid estimates for standard errors of latent abilities even when the numbers of items and subjects are not large. © 2008 Sage Publications.

Social skills are positive abilities that help children to interact with others in various situations. Many previous studies have found that failure in acquiring social skills or atypical development of social skills is predictive of later problem behavior, social maladjustment, and low academic achievement. Currently, however, few scales exist to measure the social skills of Japanese preschoolers. In Study 1, a large-scale cohort study was used to develop a scale that enables an appropriate measure of individual differences in preschoolers' social skills. The obtained 3-factor structure was consistent with published studies done in Western countries, and the scale was found to have excellent internal consistency and temporal stability. In Study 2, the relation between the newly developed scale, problem behavior, and autistic tendencies was analyzed. The results confirmed that the present scale demonstrates both concurrent and predictive validity. It is possible that early intervention based on screening with this scale might assist children to develop soundly.

Background: The purpose of this paper is to describe the gender differences of the Interaction Rating Scale (IRS) as an evidence-based practical index of children's social skills and parenting. Methods: The participants in our study, which was conducted as part of a Japan Science and Technology Agency (JST) cohort study project, were 370 dyads of children with their caregivers were followed up and surveyed at aged 18, 30, and 42 month. The participants completed the five minute interaction session and were observed using the IRS. Results: The results indicated the gender differences of IRS scores. Girls got rather high score at all ages. IRS can measure children's social skill development and parenting with high validity. Along with the qualitative differences of interaction between boys and girls, the IRS is effective in describing features of social skill development and parenting. Conclusion: The IRS provides further evidence of the fact that in order to study children's social skill development, it is important to evaluate various features of the caregiver-child interaction as a predictor of social skills. © 2010 Elsevier Ltd. All rights reserved.

Research has shown that personality traits have strong predictive validity for economic variables (e.g., income, work attainment) and epidemiological variables (e.g., longevity, physical health), as well as for psychological variables such as problem behaviors, and mental disorders. Importantly, personality traits are predictive even after controlling for socioeconomic status and cognitive abilities. The authors believe that current personality research in Japan almost completely overlooks this perspective. In this article, the authors review these new trends in personality psychological research. They propose a model for research involving A (accurate assessments), B (big samples), C (controlling for covariates and confounders), D (developmental trajectories), and E (economic and epidemiological variables). They outline three future directions to embody personality psychology for prediction, prevention, public wealth, and population health.

Background: There are still a lot of unknown aspects about the childhood development of sociability which are based on neuroscientific basis. Purpose of the Japan Children's Study (JCS) was to verify the normal process of child development of sociability; the trajectory and factors related development of sociability, and to collect findings and integrate the knowledge to make the plan of long-term and large scale cohort study. Methods: A child cohort study underway in Japan since 2005. There are the cohort study including a infant cohort study at age of 4 months to 30 months and a preschool cohort study at age of 5 years old to 8 years old. Questionnaires, direct observation of children and cognitive testing were performed. Results: In infant cohort study, 465 infants were recruited at 4 months and 367 children were followed up to 30 months, follow up rate was 78.9% and in the preschool cohort study, total 192 children (112 at 2005 and 80 at 2007) at age of 5 years old and 169 followed up to 6 years (follow up rate was 88.0%), and 79 children were followed up to 8 years old (follow up rate was 70.5%) old. Several new measurements to evaluate child sociability were developed. Some factors related to development of child sociability were found for example the 'praise' was related to child sociability in cohort study based on neuroscience findings. Conclusions: Though the trajectory of child sociability development were not clarified, some significant factors related to development of sociability, and the basic findings to conduct a long-term and large scale cohort study were provided. © 2010 by the Japan Epidemiological Association.