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Santa hats? Check. But do most Christians - and others who call themselves religious - attend services in the U.S.?

For many families, Christmas Eve means a trip to church. Two in five Americans say they regularly attend religious services. At least, that's what they say when asked by pollsters. What they actually do, however, may be quite different. Are Americans any more religious than people in other Western countries? We turn to Shankar Vendantam, author of The Hidden Brain: How Our Unconscious Minds Elect Presidents, Control Markets, Wage Wars and Save our Lives.