Which developmental theorist focused on the deep, unconscious motives that drive human thinking and behavior? pavlov?

I believe the answer is: Sigmund Freud

He was the first psychologist that popularised the idea of subconscious, which is a state of mind that exist underneath our normal thought which might influence our behaviour without being realised. 

This concept of unconscious motives bring us one step closer to understanding the cause of many psychological disorders such as psychopathy or multiple personalities.

True. you know, tools like shovels.