Final answer:
Sigmund Freud was the theorist who emphasized that slips of the tongue can reveal underlying personality dynamics related to psychological disorders.
Step-by-step explanation:
The individual who emphasized that slips of the tongue often reveal the personality dynamics that contribute to psychological disorders was Sigmund Freud. Freud famously proposed the first comprehensive theory of personality, which included the id, ego, and superego, as well as the concept that much of our mental life takes place outside of our conscious awareness. His psychoanalytic theory delves into how slips of the tongue (or Freudian slips) can be expressions of unconscious desires or conflicts.