How does Charlie's attitude change after his operation?

After his operation, Charlie becomes much more intelligent. We see his vocabulary change and his spelling improve. However, he also becomes much less gullible. He realizes, as he did not before, that he has been used as a lab rat, as the subject of an experiment, just like the mouse Algernon. His attitude towards the other adults around him becomes less worshipful and respectful as he realizes they are just ordinary human beings who might not necessarily have his best interest at heart. For example, he writes:

Dr. Nemur said that Dr. Strauss was nothing but an opportunist who was trying to ride to glory on his coattails.
When I left afterwards, I found myself trembling. I don't know why for sure, but it was as if I'd seen both men clearly for the first time. I remember hearing Burt say that Dr. Nemur had a shrew of a wife who was pushing him all the time to get things published so that he could become famous. Burt said that the dream of her life was to have a big-shot husband.

He experiences loneliness because of his high intelligence, and begins to feel much greater kinship for Algernon. He records:

People don't talk to me much any more or kid around the way they used to. It makes the job kind of lonely.

His attitude toward Miss Kinnian also changes. Where he once thought of her as a genius much older than him, he now realizes that she is only 34. He realizes he can date her. His attitude changes from seeing her as unattainable to falling in love with her.