>That is not a personality change, but a preconceived idea change. A personality change would be becoming from a serial killer the wonderfull person on earth and that for real.
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>To answer to the original question, I don't think personality change once set.

I think I agree with you, but what about something like diet as an example? A person who wants to lose a significant amount of weight must change their personality to some degree to lose the weight, and keep it off. Just losing the weight, would simply be a change of actions, but keeping it off would be a more systemic change. If someone has done that, haven't they changed an essential portion of who they are?