Why this correlation between IQ and religous belief?

I was looking at a mensa statistics and survey data released in their monthly and they had pointed out a high correlation between low range IQs and religous belief, (religous people had 10 times the likely hood of a low IQ score) conversely those with high IQs were most likely to be atheist. Also none of the top scorers were religous. The surveys and tests were for a group of 100,000 and taken in 2007. What does this mean for the general intelligence of believers in the sky pixie?