Abstract

Age	N	Boys	Girls
5–6	400	87.9	96.0
11–12	400	79.6	84.1
15–16	400	55.7	70.4

2.4. (4) Decline of religious belief during the course of the twentieth century as the intelligence of the population has increased
There is evidence for a decline of religious belief during the course of the last 150 or so years, while at the same time the intelligence of the population has increased. The increase in intelligence is a well-documented phenomenon that has become known as the Flynn effect. The decline of religious belief has been shown by statistics for church attendance and for belief in God recorded in opinion polls. For instance, in England self reported weekly attendance at church services in census returns (these numbers may be exaggerated) declined from 40% of the population in 1850, to 35% in 1900, to 20% in 1950, to 10% in 1990 (Giddens, 1997, p.460); Church of England Easter week communicants declined from 9% of the population in 1900 to 5% in 1970 (Argyle and Beit-Hallahmi, 1975 M. Argyle and B. Beit-Hallahmi, The Social Psychology of Religion, Routledge and Kegan Paul, London (1975).Argyle & Beit-Hallahmi, 1975); the attendance of children at Sunday schools declined from 30% of the child population in 1900 to 13% in 1960 (Goldman, 1965). In Gallup Polls 72% of the population stated in 1950 that they believed in God (Argyle, 1958), but by 2004 this had fallen to 58.5% (Zuckerman, 2007).
There has also been some decline of religious belief during the course of the last century in the United States. Hoge (1974) has reviewed several surveys that have found a decline of religious belief in college students. For instance, students at Bryn Mawr were asked whether they believed in a God who answered prayers. Positive responses were given by 42% of students in 1894, 31% in 1933, and 19% in 1968. Students enrolling at the University of Michigan were invited to provide a “religious preference”. In 1896, 86% of students did so; in 1930 this had dropped to 70%, and in 1968 it had dropped to 44%. At Harvard, Radcliffe, Williams and Los Angles City College the percentages of students who believed in God, prayed daily or fairly frequently, and attended church about once a week all declined from 1946 to 1966. Heath (1969) has also reported a decline in belief in God among college students from 79% in 1948 to 58% in 1968. Among the general population, Gallup Polls have found that 95.5% stated that they believed in God in 1948 (Argyle, 1958), but by 2004 this had fallen to 89.5% (Zuckerman, 2007).

3. Religious belief and psychometric g

To determine whether there is negative relation between religious belief and Psychometric g (the general factor in intelligence), the data from the National Longitudinal Study of Youth (NLSY97) have been analysed. The NLSY97 is a national sample selected to represent approximately 15 million American adolescents in the age range of 12–17 years in 1997. The subjects (N = 6825) were asked about current religious preferences in addition and took the Computer Adaptive form of the Armed Services Vocational Aptitude Battery (CAT-ASVAB97). This test consists of twelve scales (10 power and 2 speeded). These were analysed in terms of Raschian probabilistic modelling and the resulting one-dimensional scale correlated .992 (Psychometric R) with general intelligence, g, (Principal Axis Factor Analysis (t(N − 2) = 662.62; p < .000). Atheists scored 6 g-IQ equivalent points higher than the combined group of subjects professing to one or another of a large number of different religions. The difference in general intelligence among atheists and believers was significant even without using weighted data (t(1, 6.893) = 2.87; p = .004).

4. Intelligence and religious belief between nations

To investigate the relationship between intelligence and religious belief between nations we have taken the IQs of nations given in Lynn and Vanhanen’s (2006) IQ and Global Inequality. This source shows that these national IQs have high reliability, as shown by the correlation of .92 between different measures, and high validity, as shown by the correlation of .83 between the IQs and educational attainment. The high reliability and validity of these national IQs have been confirmed by Rindermann (2007). We have taken figures for belief in God from Zuckerman (2007) who gives data for 137 countries representing just over 95% of the world’s population. These data were collected from surveys mostly carried out in 2004, although in a few countries the surveys were a year or two earlier. Zuckerman collated these data from a number of different surveys in order to provide results that were as up-to-date as possible. Where he published more than one survey result for a given country we took the most recent one where this was indicated, but averaged them out where it was not. Zuckerman‘s figures consist of the percentages saying that they disbelieved in God, rather than the more frequent question asking for belief in God. Zuckerman draws attention to four problems associated with this data set. These are possible low response rates, weaknesses in random sample selection, regime or peer pressure influencing responses and problems of terminological variation between cultures over words such as ‘religious’ or ‘secular’. Despite these possible sources of error however Zuckerman urges acceptance of the data by quoting Robert Putnam to the effect that “we must make do with the imperfect evidence that we can find, not merely lament its deficiencies.”
The data for the national IQs and percentages asserting disbelief in God for the 137 countries are given in the Appendix A. It will be seen that in only 17% of the countries (23 out of 137) does the proportion of the population who disbelieve in God rise above 20%. These are virtually all the higher IQ countries.
The correlations between the national IQs and religious disbelief are given in Table 3. Row 1 gives the correlation of 0.60 for the total sample and is highly statistically significant (p < .001). To examine whether this relationship holds across the whole range of national IQs we have divided the nations into two groups of those with IQs between 64–86 and those with IQs between 87–108. Row 2 gives the data for the 69 countries with IQs between 64–86. In this group only 1.95% of the population are non-believers. There is a range between < 1% and 40%, and the correlation between the two variables is only 0.16. Row 3 gives the data for the 68 countries with IQs between 87–108. In this group 19.99% of the population disbelieve in God. There is a range between < 1% and 81%, and the correlation between the two variables is only 0.54 (p < .001). Thus, most of the variation in religious disbelief is among the higher IQ nations.

5. Discussion

The results raise four points of interest. First, the hypothesis with which we began this study was that there is a negative correlation between IQ and religious belief. We have reviewed considerable evidence for this negative relationship among individuals in the United States and Europe and have added a new data set confirming this. Second, we have shown that the negative relationship between intelligence and religious belief is a difference in Psychometric g. Third, we have extended 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 60 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%) 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 been transmitted as a cultural and even genetic legacy to subsequent generations. Parent–child correlations for religious belief are quite high at 0.64 (fathers–sons) and 0.69 (mothers–daughters) (Newcomb & Svehla, 1937). It has been found that religious belief has a significant heritability of around 0.40–0.50 (Koenig, McGrue, Krueger & Bouchard, 2005), so it could be that a number of religious emigrants from Europe had the genetic disposition for religious belief and this has been transmitted to much of the present population.

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