Phillip's brain has slowed in overall development but has experienced the most rapid development in the areas of the brain associated with language, thinking, and spatial relationships. We can assume that Phillip is in what age range?

middle childhood (7-11 yrs)

Explanation:

Middle childhood: In psychology, the middle childhood period usually starts at the age of six years of a child and lasts through eleven years of age and is determined as a time-period in which children tends to develop "foundational skills" in order to build healthy "social relationships" as well as they learn different roles in order to get prepared for adolescence and adulthood.

Main characteristics include the development of the mental, physical, and social skills.