Abigail’s teacher has witnessed a change in the complexity of Abigail’s play. Abigail used to love to stack blocks and then push them over. Recently, Abigail has begun to build houses with the blocks instead of just a stack to knock over. She asks her teacher to keep her houses each time she builds one and not put away the blocks so she can show her father when he picks her up. According to Erikson, what is Abigail developing?