Answer: This illustrates the concept of COGNITIVE DEVELOPMENT.
Explanation: Cognitive Development is a field in Psychology and Neuroscience that deals with a child's development in mental functions that deals with logic, as opposed to affective which deals with emotions.
This involves learning languages, learning skills, and other aspect of a fully developed brain.
As can be deduced from the Question, he started by recitation, then understanding the meaning of the pledge to then the importance of the pledge. All these are different stages of development.