physically interacting with the environment
interpreting their experinece
regulating their behaviour
eliciting reactions from other people
development progressing through a series of qualitatively distinct stages
when children are in a given stage, a fairly broad range of their thinking and behaviour exhibits the features characteristic of that stage
the stages occur in the same order for all children
transitions between stages occur quickly
genetics
baby’s temperament, and parent’s attitude and responsiveness that influence the quality of attachment