More detailed answer: It takes me reading/hearing something at least three times before I find myself more willing to rethink a stance I hold. It's very rare (especially outside of counseling) to have my mind changed with a single declaration. One of the reasons I need repetition is so I can do some digging on the person or group making the statement that runs contrary to my views. I want to find out more of what's motivating them to make the statement (and if data is collected what methods they use). If I see multiple sources that don't have a vested interest in the issue make the contrary statement, I'm more willing to revise my stance. That way I know it's truly my brain making the choice and not me being emotionally manipulated.