I have no idea if this is true or not, but have two comments to make.
1. I'm just not convinced that academics have higher IQ's than average (although I'd be happy for someone to direct me towards some evidence). Some are profoundly brilliant but I think acadamia benefits more from the doggedness and hard work of many, combined with long training, rather than from a better average rate of intelligence.
2. On the other hand, Professor Lynn says that academics do have higher IQs, so I assume there is some evidence to support this (otherwise he would hardly say it?)
Professor Lynn told Times Higher Education: "Why should fewer academics
believe in God than the general population? I believe it is simply a matter of
the IQ. Academics have higher IQs than the general population. Several Gallup
poll studies of the general population have shown that those with higher IQs
tend not to believe in God."
In the TLS report, the idea that there is a causal relationship here is immediately questioned (and I suspect with good cause). I myself was amused by Professor Lynn's statement that he believes it is simply a matter of IQ. I think it is pretty honest of him to say so - and makes me a lot more inclined to listen to his opinion.
On the spectrum of belief I find myself close to atheism, but I find a link between intelligence and belief hard to buy. Doubting received wisdom is surely a good sign of intelligence, but what a person does with that doubt, whether it leads to belief or non-belief, or something in between, seems little linked to their intelligence. Non-believers sometimes imply that belief is a result of not thinking about the big question. It strikes me that non-belief can as often as not result from the same reluctance to wonder.