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 (helping people cope) 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, mindfullness, 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. According to biopsychologist Nigel Barber, the differences in national IQ are better explained by social, environmental, and wealth conditions than by levels of religiosity. He acknowledges that highly intelligent people have been both religious and nonreligious. He notes that countries with more wealth and better resources tend to have higher levels of non-theists and countries that have less wealth and resources tend to have fewer non-theists. For instance, countries that have poverty, low urbanization, lower levels of education, less exposure to electronic media that increase intelligence, higher incidence of diseases that impair brain function, low birth weights, child malnutrition, and poor control of pollutants like lead have more factors that reduce brain and IQ development than do wealthier or more developed countries. 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. Studies examining