People with higher IQs are more likely not to believe in a mythical Deity,
Professor Richard Lynn, emeritus professor of psychology at Ulster University, said many more members of the "intellectual elite" considered themselves atheists.
The decline in religious observance over the last century is directly linked to a rise in average intelligence, he said.
Professor Lynn, who has provoked controversy in the past with research linking intelligence to race and sex, said university academics were less likely to have religious beliefs than almost anyone else.
A survey of Royal Society fellows found that only 3.3 per cent believed in God - at a time when 68.5 per cent of the general UK population described themselves as believers or agnostic.
A separate poll in the 90s found only seven per cent of members of the American National Academy of Sciences believed in God.
Professor Lynn said most primary school children believed in God, but as they entered adolescence - and their intelligence increased - they started to question the belief system.
"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 do not to believe in God."
He said religious belief had declined dramatically across 137 developed nations in the 20th century at the same time as people became more intelligent.
But Professor Gordon Lynch, director of the Centre for Religion and Contemporary Society at Birkbeck College, London, said it should have also taken into account the complex range of social, economic and historical factors.
"Linking religious belief and intelligence in this way would encourage the trend of developing a simplistic characterisation of religion as primitive" he said.
Dr David Hardman, principal lecturer in learning development at London Metropolitan University, said: "It is very difficult to conduct true experiments that would explicate a causal relationship between IQ and religious belief. Nonetheless, there is evidence that higher levels of intelligence are associated with a greater ability - to question and overturn strongly felt religious beliefs."