Some argue that faith or lack thereof indicates intelligence, but it’s really more indicative of culture.
A quick note: believing in a particular god does not make one stupid, or a bad person. That does not mean that one is not stupid for believing mutually contradictory things about that god, or a bad person for endorsing immoral acts due to that belief.
-Links for the Curious-
A study by Vern Bengston et. al about how religion is, unsurprisingly, passed from parents to children – iss.sagepub.com/content/24/3/325.short
An interesting summary of ideas regarding geography and its influence on the spread of certain religions – www.lancaster.ac.uk/staff/gyaccp/geography%20and%20religion.pdf
Penn Jilette on atheism – www.youtube.com/watch?v=Q0N6bh_qB58