"Those who scored the highest were atheists and agnostics,"

I'm sure this would also be the case in Britain, which is why I get so angry with mindless, arrogant evangelicals I have come across (including members of my own family) who believe that they have a god-given duty to bring to the lord the poor, ignorant, benighted godless sinners who don't know the error of their ways. Athiests have usually made a rationale, considered decision to be so and are unlikely to be swayed by what they consider to be superstitious nonsense.