Which person was most interested in studying learned behavior? pysch?

The type of person most interested in studying learned behavior would be a Psychologist.

More specifically a Behavioral Psychologist - Behaviorists believe that human behavior is shaped by our responses to environmental stimuli, in other words how external events shape our behavior.

Behavioral psychology, is a theory of learning based on the idea that all behaviors are acquired through conditioning. Conditioning occurs through interaction with the environment.