Final answer:
The creature's statement about frightening himself into silence indicates a higher level of sophistication and self-awareness.
Step-by-step explanation:
When the creature makes the statement, "The uncouth and inarticulate sounds which broke from me frightened me into silence again," it reveals that the creature's current state is one of increased self-awareness and complexity. It shows that he is more sophisticated than he used to be because he is now capable of evaluating his own actions and behaviors and the sounds he made caused him fear, indicating a developed sense of self and understanding of his difference from what he presumably perceives as 'normal' speech or communication.