He will be more sympathetic to those who are similar to the way he once was.
Explanation:
From the book, "Flowers for Algernon" by Daniel Keyes, Charlie Gordon was once mentally ret*rded but he became more intelligent after he underwent surgery.
He has an experience in the diner one day after a mentally ret*rded boy mistakenly crashes some plates and receives cruel taunts from the other customers and the boy who does not know he is being taunted and insulted, smiles with them and this episode makes Charlie so angry that he shouts to the insensitive crowd that the boy is a human and thus deserves respect.
This experience would likely change Charlie because He will be more sympathetic to those who are similar to the way he once was.
