This study reports on co-occurrence of vocal behaviors and motor actions in infants in the prelinguistic stage. Four Japanese infants were studied longitudinally from the age of 6 months to 11 months. For all the infants, a 40 min sample was coded for each monthly period. The vocalizations produced by the infants co-occurred with their rhythmic actions with high frequency, particularly in the period preceding the onset of canonical babbling. Acoustical analysis was conducted on the vocalizations recorded before and after the period when co-occurrence took place most frequently. Among the vocalizations recorded in the period when co-occurrence appeared most frequently, those that co-occurred with rhythmic action had significantly shorter syllable duration and shorter formant-frequency transition duration compared with those that did not co-occur with rhythmic action. The rapid transitions and short syllables were similar to patterns of duration found in mature speech. The acoustic features remained even after co-occurrence disappeared. These findings suggest that co-occurrence of rhythmic action and vocal behavior may contribute to the infant's acquisition of the ability to perform the rapid glottal and articulatory movements that are indispensable for spoken language acquisition.

The onset of canonical babbling (CB) is a landmark event in infants’ vocal development for spoken language. Previous research has suggested that the onset of CB coincides with the peak period of rhythmic activities. To examine this phenomenon in detail, 28 Japanese infants (14 girls, 14 boys) were observed longitudinally from the age of 5 to 9 months. In the experimental sessions, an audible or an inaudible rattle was placed into a hand of each tested infant. Then the number of times that the infant shook the rattle was counted. In the observational sessions, infants’ spontaneous rhythmic activities under natural conditions were observed. The result shows that rhythmic activities reached their peak around the onset of CB. When the infants began to babble, they shook whichever rattle was in their hand, regardless of its audibility. After this period, they shook the audible rattles more frequently than the inaudible ones. These findings suggest that, around the onset of CB, infants learn to control their motor activities based on auditory feedback.

Objectives: This study investigated employment, financial, and health issues of Japanese mothers with schoolaged children with disabilities, and factors associated with participants' employment. Methods: A survey was conducted with 243 Japanese mothers with children aged 6 to 18 years old enrolled in a Special Education Needs School for intellectually disabled children. The mothers' employment, income, health, and time spent caregiving were compared with those of other Japanese mothers using population data. Multiple logistic regression analysis was conducted to identify factors associated with the mothers' employment status. Results: Participants showed a lower employment rate (49%) compared with the average rate (71%) among Japanese mothers with children aged between 6 and 18 years old who lived in the same region. Over half (57%) of unemployed mothers expressed a desire to work. About 62% of mothers belonged to a lower income group, compared to 33% of Japanese families rearing children. The mothers' single-parent status, good health, collegelevel education, use of childcare services, and children's age were positively associated with paid employment. In particular, mothers' good health was strongly associated with their paid employment. Conclusion: Mothers caring for children with disabilities showed lower workforce participation and lower income than other Japanese mothers. The majority of unemployed mothers showed a desire for paid employment. Further maternal health care and social support are needed to support these mothers' workforce participation.

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