The early sociability of toddlers: The origins of teaching

•Toddlers’ person-directed behaviors were recorded longitudinally in a naturalistic preschool setting.•In the first session, the Giving category had the highest incidence, but Verbalization grew dramatically afterward.•Explaining was observed in a 17 months girl.•This study shows children's altruistic behaviors in natural setting.

Toddlers’ person-directed behaviors were recorded longitudinally in a naturalistic preschool setting. An observer (O, the author) recorded children's behaviors with an IC recorder during play sessions. Seventeen children, as a group, were observed once a week in 3 blocks of 7 weeks (21 total hours). Person-directed behaviors toward the observer increased with each block. Toddlers’ teaching behaviors were classified precisely. This teaching classification should be the first event of the origins of teaching.