In the western world, average IQs have shown remarkable gains over the course of the twentieth century (Flynn, 1984, 1987, 2007). These gains have been largest for non-verbal tests once considered relatively impervious to cultural influences, such as the Raven's (Brouwers et al., 2009). For instance, in the Netherlands an unaltered version of the SPM [Raven's Standard Progressive Matrices] was administered to male military draftees from 1952 to 1982. The 1982 cohort scored approximately 20 IQ points higher than the 1952 cohort (Flynn, 1987). In this section, we consider whether a Flynn Effect has occurred among Africans on the Raven's tests.
Proposed causes of the Flynn Effect include improvements in test-specific skills (Greenfield, 1998; Wicherts et al., 2004), improvements in nutrition (Lynn, 1989, 1990), urbanization (Barber, 2005), improvements in health care (Williams, 1998), a trend towards smaller families (Zajonc & Mullally, 1997), increases in educational attainment (Ceci, 1991), greater environmental complexity (Schooler, 1998), and the working of genotype by environment correlation in the increasing presence of more intelligent others (Dickens & Flynn, 2001). Many of these environmental variables have not undergone the improvement in developing sub-Saharan African countries that they have in the developed world over the last century. This suggests that the Flynn Effect has great potential in sub-Saharan Africa (Wicherts, Borsboom, & Dolan, 2010b).
Although the implications of our psychometric findings for the potential of the Flynn Effect in sub-Saharan Africa remain unclear, the Raven's tests and other IQ tests have shown robust increases in many populations (Daley et al., 2003; Flynn, 2007). So suppose that there were a well-validated IQ test that showed measurement invariant scores between westerners and Africans. Even then, lower IQs of Africans still would not support Lynn and Vanhanen's (2002, 2006) assertion that countries in sub-Saharan Africa are poorly developed economically because of their low "national IQ". Wicherts, Borsboom, and Dolan (2010b) found that "national IQs" are rather strongly confounded with the developmental status of countries. Given the well-documented Flynn Effect, we know that "national IQs" are subject to change. An average IQ around 80 among Africans may appear to be low, but from a historical perspective this average is not low at all. A representative sample of British adults, who took the SPM in 1948 would have an average IQ of 81 in terms of the British norms of 1992 (J. C. Raven, 1960; J. C. Raven et al., 1996). Using older British norms, the average IQ of Africans would be much closer to 100. This is evident in Figure 2, where we compared SPM scores of Africans to older norms. In this figure, the average IQ of several African samples is near or above 100.
Present-day sub-Saharan Africa is one of the poorest regions in the world and the home to some of the world's most deprived children. The majority of sub-Saharan children are chronically malnourished, not only from lack of food but particularly from food lacking vital elements related to both physical growth and intellectual development. It has been estimated that up to 70 percent of rural children live in absolute poverty and 90 percent suffer severe deprivation (Gordon, Nancy, Pantazis, Pemberton, & Townsend, 2003). A substantial number of sub-Saharan African children are under-educated. According to Garcia, Gillian, and Dunkelberg (2008), only about 12 percent of sub-Sahara African children have attended preschool, and this generally for well less than a year. They note that children who do not attend or have only minimal experience in pre-primary school tend to do less well in primary school than children who have had that experience. Further, it is important that the preschool experience be successful. For example, Jaramillo and Mingat (2008) have shown that children who have a poor experience in preschool and have to repeat a year or part of a year have a high drop-out rate in primary school (r = -0.875). The probability of preschool without repetition and who complete primary school is low but positive (r = 0.209). With or without preschool experience, approximately only fifty-five percent of 10-14 year-olds in sub-Saharan Africa complete primary school.
Many of the variables that have been proposed as causes of the Flynn Effect (e.g., Barber, 2005; Ceci, 1991; Dickens & Flynn, 2001; Greenfield, 1998; Lynn, 1989; Schooler, 1998; Williams, 1998) have yet to undergo improvement in developing sub-Saharan African countries that they have enjoyed in the developed world over the last century. Because the environmental variables that potentially contribute to enhanced IQ have yet to improve in the countries of sub-Saharan Africa, we regard the Flynn Effect as still in its infancy. There is in fact considerable empirical support that (mal)nutrition (Grantham-McGregor & Baker-Henningham, 2007; Sigman & Whaley, 1998), health (Williams, 1998), sanitation (Boivin et al., 1993), and schooling (Ceci, 1991) have an effect on IQ. The UN have included such variables in the so-called Millennium Goals, i.e., they are targeted for improvement by 2015 (United Nations, 2005). The formulation of the Millennium Goals provides an interesting opportunity to evaluate the effect of these factors on IQ levels in sub-Saharan Africa. There is now a clear indication that the Flynn Effect seems to have come to a halt in developed nations (Flynn, 2007). It is, therefore, reasonable to think that as circumstances in sub-Saharan Africa improve, the IQ gap between western samples and African samples will diminish.
The vast literature on IQ testing with the Raven's tests in Africa does not support James Watson's pessimism concerning the prospects of Africa. It is true that Africans show lower average IQs as compared to contemporary western norms, although the IQ gap is substantially smaller than Lynn (and Vanhanen) have maintained. More importantly, there is little scientific basis for the assertion that the observed lower IQs of Africans are evidence of lower levels of general intelligence or g. The validity of the Raven's tests among Africans needs to be studied further before these tests can be used to assess Africans' cognitive ability in educational and professional settings. There are several reasons to expect increases in IQ levels among sub-Saharan Africans in the coming decades.
Wicherts et al. "Raven's Test Performance of Sub-Saharan Africans: Average Performance, Psychometric Properties, and the Flynn Effect". Learning and Individual Differences, 2010.