Simplify the following text for a Grade 9 native English-speaking person.
Original: Probably the most detailed and precise of the various notions of ` unconscious mind ' â '' and the one which most people will immediately think of upon hearing the termâ '' is that developed by Sigmund Freud and his followers . It lies at the heart of psychoanalysis .
Simplified: The unconscious mind plays a large role in Sigmund Freud 's psychoanalysis .