A term for the
developmental sequence. This emphasises two facets of typical development: (1)
There is a characteristic sequence of 'milestones' such as crawling, sitting up
and walking. (2) Early developmental skills such as pointing and looking are
thought to lay the foundations for later more sophisticated skills such as play
with siblings, friendships with peers, or the complex relationships of the
teenage years and adulthood. The idea of an atypical developmental trajectory
is an important concept in work on autism.