Developmental chronology of preverbal social behaviors in infancy using the M-CHAT: Baseline for early detection of atypical social development

This study aimed to identify the age of emergence and subsequent order of preverbal social behaviors, which have not yet been fully clarified. This was accomplished using 16 items of social behaviors extracted from the Modified Checklist for Toddlers with Autism (M-CHAT). The Japanese version of the M-CHAT was completed voluntarily by the parents of 318 infants aged 8–20 months. The 16 social behaviors can be divided roughly into three behavior sets based on the age at which 75% of the answers to the corresponding items were positive: the first set of 6 items emerged before 8 month old; the second set of 6 items, did between 11 and 12 month old; and the third set of 4 items, did after 15 month old. In addition, the subsequent order and synchrony among items were determined: Imitation, Point following, and Attracting parent's attention emerged earlier than Pretend play and Imperative/Declarative pointing in the second set; further, Gaze following and Social reference emerged earlier than Bringing objects to show and Functional play in the third set. This study provides an evidence-based developmental chronology of a wide range of preverbal social behaviors, which can serve as a baseline for assessing atypical social development in infants.