Final answer:
The cognitive change that has occurred in the little boy is the development of theory of mind (TOM), which involves recognizing that others can have thoughts, feelings, and beliefs that differ from one's own.
Step-by-step explanation:
The cognitive change that has occurred in the little boy is the development of theory of mind (TOM). Theory of mind refers to the understanding that people have thoughts, feelings, and beliefs that may be different from one's own. It involves recognizing that others can have false beliefs.
Before the age of 3 to 5, children are typically egocentric and do not have an awareness of others' points of view. However, as they develop theory of mind, they become more capable of understanding others' perspectives, which allows them to engage in various social interactions and activities.
In this case, the little boy's experience of receiving his first Lego kit for his birthday can be considered as a result of his cognitive development of theory of mind.