Answer:
"Gay '90s" : functionalism
"Roaring '20s" : Gestalt psychology
Explanation:
Functionalism and Gestalt psychology are the two theories of psychology.
Functionalism highlights the theory of mental states of the individuals. In this theory, the constitution of the mental states are not focused, rather their functions are focused.
Gestalt psychology highlights on the completeness of the things. This theory focuses on complete things rather than individual or its parts.