We arduously convince young children to believe in Santa, and they do. Testimony dictates religious beliefs, too. For example, psychologist Rebekah Richert has found that if you frame a fantastical story as a religious story, children raised in religious households will believe it. If you don't frame it religiously, they'll call your bluff.
When we get to college, however, cultural testimony changes. An analytical, scientific view reigns, and there's little room for God. We staggered home from parties pontificating on the pointless evil of Western religion. We made friends by cynically confessing our doubt. College is "very likely to challenge the more conservative belief systems we have in our brains," Grafman says. It deflates our adolescent faith.