Religiosity and intelligence

The study of religiosity and intelligence explores the link between religiosity and intelligence or educational level. Religiosity and intelligence are both complex topics that include diverse variables, and the interactions among those variables are not always well understood. For instance, intelligence is often defined differently by different researchers; also, all scores from intelligence tests are only estimates of intelligence, because one cannot achieve concrete measurements of intelligence due to the concept's abstract nature. Religiosity is also complex, in that it involves wide variations of interactions of religious beliefs, practices, behaviors, and affiliations, across a diverse array of cultures.
The study on religion and intelligence has been ongoing since the 1920s and conclusions and interpretations have varied in the literature due to different measures for both religiosity and intelligence. Some studies find negative correlation between intelligence quotient and religiosity. However, such studies and others have found the effect not to be generalizable and unable to predict religiosity from intelligence correlations alone. Some have suggested that nonconformity, cognitive style, and coping mechanism play a role while others suggest that any correlations are due to a complex range of social, gender, economic, educational and historical factors, which interact with religion and IQ in different ways. Less developed and poorer countries tend to be more religious, perhaps because religions play a more active social, moral and cultural role in those countries.
Studies on analytic thinking and nonbelievers suggest that analytical thinking does not imply better reflection on religious matters or disbelief. A cross-cultural study observed that analytic thinking was not a reliable metric to predict disbelief. A review of the literature on cognitive style found that there are no correlations between rationality and belief/disbelief and that upbringing, whether religious or not, better explains why people end up religious or not.
A global study on educational attainment found that Jews, Christians, religiously unaffiliated persons, and Buddhists have, on average, higher levels of education than the global average. Numerous factors affect both educational attainment and religiosity.

Definitions and issues

Intelligence

The definitions of intelligence are controversial since at least 70 definitions have been found among diverse fields of research. Some groups of psychologists have suggested the following definitions:
From "Mainstream Science on Intelligence", an op-ed statement in the Wall Street Journal signed by fifty-two researchers.
From "Intelligence: Knowns and Unknowns", a report published by the Board of Scientific Affairs of the American Psychological Association:
Intelligence is a property of the mind that encompasses many related abilities, such as the capacities to reason, to plan, to solve problems, to think abstractly, to comprehend ideas, to use language, and to learn. There are several ways to more specifically define intelligence. In some cases, intelligence may include traits such as creativity, personality, character, knowledge, or wisdom. However, some psychologists prefer not to include these traits in the definition of intelligence.
A widely researched index or classification of intelligence among scientists is intelligence quotient. IQ is a summary index, calculated by testing individuals' abilities in a variety of tasks and producing a composite score to represent overall ability, e.g., Wechsler Adult Intelligence Scale. It is used to predict educational outcomes and other variables of interest.
Others have attempted to measure intelligence indirectly by looking at individuals' or group's educational attainment, although this risks bias from other demographic factors, such as age, income, gender and cultural background, all of which can affect educational attainment.
Dissatisfaction with traditional IQ tests has led to the development of alternative theories. In 1983, Howard Gardner proposed the theory of multiple intelligences, which broadens the conventional definition of intelligence, to include logical, linguistic, spatial, musical, kinesthetic, naturalist, intrapersonal and interpersonal intelligences.
He chose not to include spiritual intelligence amongst his "intelligences" due to the challenge of codifying quantifiable scientific criteria, but suggested an "existential intelligence" as viable.

Religiosity

The term religiosity refers to degrees of religious behaviour, belief, or spirituality. The measurement of religiosity is hampered by the difficulties involved in defining what is meant by the term. Numerous studies have explored the different components of religiosity, with most finding some distinction between religious beliefs/doctrine, religious practice, and spirituality. Studies can measure religious practice by counting attendance at religious services, religious beliefs/doctrine by asking a few doctrinal questions, and spirituality by asking respondents about their sense of oneness with the divine or through detailed standardized measurements. When religiosity is measured, it is important to specify which aspects of religiosity are referred to.
According to Mark Chaves, decades of anthropological, sociological, and psychological research have established that "religious congruence" is actually rare. People's religious ideas are fragmented, loosely connected, and context-dependent, as in all other domains of culture and in life. The beliefs, affiliations, and behaviors of any individual are complex activities that have many sources including culture. As examples of religious incongruence he notes, "Observant Jews may not believe what they say in their Sabbath prayers. Christian ministers may not believe in God. And people who regularly dance for rain don't do it in the dry season."
Demographic studies often show wide diversity of religious beliefs, belonging, and practices in both religious and non-religious populations. For instance, out of Americans who are not religious and not seeking religion, 68% believe in God, 12% are atheists, and 17% are agnostics; as for self-identification of religiosity, 18% consider themselves religious, 37% consider themselves spiritual but not religious, and 42% consider themselves neither spiritual nor religious, while 21% pray every day and 24% pray once a month. Global studies on religion also show diversity.
Religion and belief in gods are not necessarily synonymous since nontheistic religions exist including within traditions like Hinduism and Christianity. According to anthropologist Jack David Eller, "atheism is quite a common position, even within religion" and that "surprisingly, atheism is not the opposite or lack, let alone the enemy, of religion but is the most common form of religion."

Studies comparing religious belief and IQ

In a 2013 meta-analysis of 63 studies, led by professor Miron Zuckerman, a correlation of -.20 to -.25 between religiosity and IQ was particularly strong when assessing beliefs, but the negative effects were less defined when behavioral aspects of religion were examined. They note limitations on this since viewing intrinsic religiosity as being about religious beliefs represents American Protestantism more than Judaism or Catholicism, both of which see behavior as just as important as religious beliefs. They also noted that the available data did not allow adequate consideration of the role of religion type and of culture in assessing the relationship between religion and intelligence. Most of the studies reviewed were American and 87% of participants in those studies were from the United States, Canada, and the United Kingdom. They noted, "Clearly, the present results are limited to Western societies." The meta-analysis discussed three possible explanations: First, intelligent people are less likely to conform and, thus, are more likely to resist religious dogma, although this theory was contradicted in mostly atheist societies such as the Scandinavian populations, where the religiosity-IQ relationship still existed. Second, intelligent people tend to adopt an analytic thinking style, which has been shown to undermine religious beliefs. Third, intelligent people may have less need for religious beliefs and practices, as some of the functions of religiosity can be given by intelligence instead. Such functions include the presentation of a sense that the world is orderly and predictable, a sense of personal control and self-regulation and a sense of enhancing self-esteem and belongingness.
A 2016 re-analysis of the Zuckerman et al study, found that the negative intelligence-religiosity associations were weaker and less generalizable across time, space, samples, measures, and levels of analysis, but still robust. For example, the negative intelligence–religiosity association was insignificant with samples using men, pre-college participants, and taking into account grade point average. When other variables like education and quality of human conditions were taken into account, positive relation between IQ and disbelief in God was reduced. According to Dutton and Van der Linden, the re-analysis had controls that were too strict and also some of the samples used problematic proxies of religiosity, which took away from the variance in the correlations. As such, the reduction of significance in the negative correlation likely reflected a sample anomaly. They also observed that the "weak but significant" correlation of -.20 on intelligence and religiosity from the Zuckerman study was also found when comparing intelligence with other variables like education and income.
Zuckerman et al. published an updated metanalysis in 2019 with 83 studies finding "strong evidence" of a negative correlation between religiosity and intelligence of -.20 to -.23. Zuckerman cautioned that the "effect size of the relation is small", not generalizable beyond the Western world and that predicting religiosity from intelligence for individuals is fallible.
Researchers Helmuth Nyborg and Richard Lynn compared belief in God and IQs. Using data from a U.S. study of 6,825 adolescents, the authors found that the average IQ of atheists was 6 points higher than the average IQ of non-atheists. The authors also investigated the link between belief in a god and average national IQs in 137 countries. The authors reported a correlation of 0.60 between atheism rates and level of intelligence, which was determined to be "highly statistically significant".
Other researchers found Nyborg and Lynn's findings questionable since sporadic and inconsistent estimates were the basis for atheism rates, multiple factors better explain the fluctuations, including reversals, in both religion and IQ by nations through time; data that contradicted their hypothesis was minimized, and secularization debates among scholars were ignored, all of which rendered any predictability as unreliable.
The Lynn et al. paper findings were discussed by Professor Gordon Lynch, from London's Birkbeck College, who expressed concern that the study failed to take into account a complex range of social, economic and historical factors, each of which has been shown to interact with religion and IQ in different ways. Gallup surveys, for example, have found that the world's poorest countries are consistently the most religious, perhaps because religion plays a more functional role in poorer nations. Even at the scale of the individual, IQ may not directly cause more disbelief in gods. Dr. David Hardman of London Metropolitan University says: "It is very difficult to conduct true experiments that would explicate a causal relationship between IQ and religious belief." He adds that other studies do nevertheless correlate IQ with being willing or able to question beliefs.
In a sample of 2307 adults in the US., IQ was found to negatively correlate with self reports of religious identification, private practice or religion, mindfulness, religious support, and fundamentalism, but not spirituality. The relationships were relatively unchanged after controlling for personality, education, age, and gender, and were typically modest. The study was limited only to Christian denominations.
A critical review of the research on intelligence and religiosity by Sickles et al. observed that conclusions vary widely in the literature because most studies use inconsistent and poor measures for both religiosity and intelligence. Furthermore, they noted intelligence differences seen between people of varying religious beliefs and non-theists is most likely the result of educational differences that are in turn the result of holding fundamentalist religious beliefs rather than the result of innate differences in intelligence between them.
According to Dutton et al. negative correlations on religion may be correlated with autistic spectrum on specialized learning ability since when members of the same ethnic group are compared there are very few differences in IQ in general.
In non-western countries like Korea, where religion is seen differently than in the West, non-religious people had lower mean IQs than religious persons.
A 2022 metanalysis of 89 studies found a small and weak negative correlation of -.14 and noted that the findings were not generalizable beyond a Western contexts.