this hypothesis to an examination of whether a negative correlation between IQ and religious belief is present between countries. Using data from 137 countries we found a correlation of 0.60 between national IQs and disbelief in god. Although the measure used for the analysis across nations was for disbelief in god rather than for belief in god, we believe it can be reasonably assumed that disbelief in god is highly (negatively) correlated with belief in god. Hence, we conclude that the negative correlation between IQ and religious belief that has been found in numerous studies within nations is also present between nations.
Second, this conclusion raises the question of why should there be this negative correlation between IQ and belief in god. Many rationalists no doubt accept the argument advanced by Frazer (1922, p.712) in The Golden Bough that as civilisations developed “the keener minds came to reject the religious theory of nature as inadequate … religion, regarded as an explanation of nature, is replaced by science” (by “keener minds” Frazer presumably meant the more intelligent). Others have assumed implicitly or explicitly that more intelligent people are more prone to question irrational or unprovable religious dogmas. For instance, some sixty years ago Kuhlen and Arnold (1944) proposed that “greater intellectual maturity might be expected to increase scepticism in matters of religion”. Inglehart and Welzel (2005, p.27) suggest that in the pre-industrial world, humans have little control over nature, so "they seek to compensate their lack of physical control by appealing to the metaphysical powers that seem to control the world: worship is seen as a way to influence one's fate, and it is easier to accept one's helplessness if one knows the outcome is in the hands of an omnipotent being whose benevolence can be won by following rigid and predictable rules of contact…one reason for the decline in traditional religious beliefs in industrial societies is that an increasing sense of technological control over nature diminishes the need for reliance on supernatural powers".
Third, there are a few exceptions to the generally linear relationship between IQ and disbelief in god across nations. Two of the most anomalous are Cuba and Vietnam, which have higher percentages disbelieving in god (40% and 81%, respectively) than would be expected from their IQs of 85 and 94 (respectively). This is likely attributable to these being former or current communist countries in which there has been strong atheistic propaganda against religious belief. In addition, it has sometimes been suggested that communism is itself a form of religion in which Das Capital is the sacred text, Lenin was the Messiah who came to bring heaven on earth, while Stalin, Mao, Castro and others have been his disciples who have came to spread the message in various countries. On these grounds, it may be argued that many of the peoples of Cuba and Vietnam hold a variant of more conventional religious belief in god.
Fourth, the United States is anomalous in having an unusually low percentage of its population disbelieving in God (10.5 per cent) for a high IQ country. The percentage disbelieving in God in the United States is much lower than in north west and central Europe (e.g. Belgium, 43%; Netherlands, 42%; Denmark, 48%; France, 44%; UK, 41.5%). One factor that could provide a possible explanation for this is that many Americans are Catholics, and the percentage of believers in Catholic countries in Europe is generally much higher than in Protestant countries (e.g. Italy, 6%; Ireland, 5%; Poland, 3%; Portugal, 4%; Spain, 15%). Another possible contribution to this has been continued high immigration of those holding religious beliefs. A further possible factor might be that a number of emigrants from Europe went to the United States because of their strong religious beliefs, so it may be that these beliefs have