What cause the creature to change in the novel Frankenstein?

In my opinion, what causes the creature to change is the
way that the people in the village treat him.

The creature
has learned pretty much everything he knows by watching the people.  He has not realized
that they will be horrified by him.  He goes and talks to the old man, who accepts him
because the man is blind and cannot see his face.

But then
when the other people come back and see him, they are repulsed and they chase him away. 
It is right after this that the creature meets and kills William
Frankenstein.