Solitary (Sol) and parallel play (Par) showed a similar developmental course with an abrupt decrease between 3–4 and 4–5 years. Onlooker behaviour (Onl) which was not frequent whatever age group decreased significantly at the end of the preschool years. Children spent also less and less time unoccupied (Uno) with a significant decrease at the beginning and the end of the preschool period. More precisely, interactions with adults (Adu) showed a significant decrease from 2–3 to 4–5 years, becoming rare in the two oldest age groups.
A main age effect was found for all the categories. Age effect on the percentages of children's playtime allocation among social play categories ( F and P- values for variances analyses and P-values for Fisher's PLSD post-hoc comparisons among age groups). Table S2: Developmental trends in social participation over the preschool period.
