Numerous studies demonstrate an inverse or negative correlation between religiosity and:
► educational level
► education in science
► liberal moral attitudes
► acceptance of the fact of biological evolution
* "Of 43 studies carried out since 1927 on the relationship between religious belief and one's intelligence and/or educational level, all but four found an inverse connection. That is, the higher one's intelligence or education level, the less one is likely to be religious or hold "beliefs" of any kind." ~ Bell, Paul. "Would you believe it?" Mensa Magazine, Feb. 2002, pp. 12–13
"In 1998, most members of the National Academy of Sciences rejected the notion of God, with the highest rate of disbelief noted amongst biological scientists." Table. ~ Larson, Edward J.; Larry Witham (1998). "Leading scientists still reject God". Nature 394 (6691): 313. Available at StephenJayGould.org, Stephen Jay Gould archive.
However, intelligent, rational indoctrinees seem to be the more likely to deconvert. My impression is that fundamentalism loses more indoctrinees than mainstream religion, but this might be a false impression that results from the resentment towards religion that many fundamentalist escapees feel. Deconversion can be very painful and protracted for fundamentalists, and can result in alienation from family and friends. Resentment and a desire to help others through deconversion is understandable.