"Cognitive development in Piaget's theory is that the child’s construction of reality takes place through the use of schemes, which are cognitive structures for processing, organizing, and interpreting information" (Jensen & Arnett, 2018). 

One cognitive milestone for a six-month-old is putting things in his/her mouth to explore them.

Foods:

  A second cognitive milestone for a six-month-old is reaching to grab a toy he/she wants.

By 6 months of age an infant can close their lips to show they do not want more food.    

Enjoys playing with others, especially (“peek-a-boo”).