It might behoove us to be more cautious in reaching conclusions based on these results than based on the other studies cited for two reasons: the sample (N = 79) is a relatively small and the WAIS IV manual does not tell us the degree to which it is representative of the French population in terms of variables such as education or geographic region. Clearly, it cuts out those who are under the age of 30 years or over the age of 63 years, but its average age (45 years) is approximately similar to the median age of the French population, which is 42.4 years as of 2014 (Central Intelligence Agency, 2015). In addition, the Full Scale IQ on the WAIS IV sample of 79 subjects was calculated based on a comparison with the WAIS IV sample of 876 subjects, which was representative of the French population on key variables such as education and region. The scores of this sample of 876 subjects were set at 100 and a comparison made with the sample of 79 subjects. As can be seen in Table 4, on this basis the IQ of the sample of 79 subjects was 101.1 with an SD of 14.7, where the French norm would be 100 and the SD 15. As such, the smaller sample can be regarded as representative of the French population in terms of intelligence.
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Secondly, the results for France, for the subtests given in Table 3, show substantial differences in the rates of the decline of different abilities. The largest declines were in Vocabulary (.43d), Comprehension (.32d) and Information (.34d) and the results in Table 4 confirm these by showing the largest decline of 4 IQ points in the Verbal Comprehension Index. Table 3 also shows that Symbol Search was the only subtest that did not show a decline but registered a small increase (.05d). In the Symbol Search test the examinee visually scans two groups of symbols, a target group (composed of two symbols) and a search group (com- posed of five symbols), and indicates whether any of the target symbols match any of the symbols in the search group. The score is the number of correct responses obtained in 2 min.
Thirdly, the results show no change in the Digit Span subtest. This confirms the conclusion of Gignac (2015) that there was no change in forward or backward digit span in the United States over the 85 years from 1923 to 2008. The present results also show that there was no change in the Working Memory Index of which digit span is a component.
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These immigrants are likely to have had some impact on reducing the average IQ of the populations, but it is doubtful whether the increase in the number of immigrants with lower IQs has been sufficiently great to have had a major effect. For instance, in Norway it was shown by Sundet, Barlaug, and Torjussen (2004) that immigrants comprised approximately 2–3% of their conscript samples and that these would have reduced the IQ by only around 0.1–0.2 IQ points (correspondence with Sundet, quoted in Dutton, 2014). In addition, Dutton and Lynn (2013) have observed a decline in IQ scores among Finnish military conscripts from 1997, despite a negligible number of non-Europeans in Finland of the appropriate age at that time. Furthermore, increasing numbers of immigrants with lower IQs than the host population has apparently had no effect in reversing the Flynn Effect in the United States
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Replacement migration in France involving populations exhibiting lower means of IQ and higher rates of total fertility, such as Algerians, Moroccans, Tunisians and Roma (
Čvorić, 2014 and
Lynn and Vanhanen, 2012) may be increasing the rate of secular losses at the level of g, consistent with speculations advanced in
Dutton and Lynn (2015), however the additional loss in g due to this process is anticipated to be very small. Based on a simulation,
Nyborg (2012)estimates that in Denmark, replacement migration may be reducing heritable g by .28 points per decade, which would increase the overall loss in gto 1.51 points per decade (
Woodley of Menie, 2015), this still being only 37.75% of the loss observed in the French cohort.
Another possible contributing factor is the so-called “brain drain” (
De Rugy, 2012), which involves high-g French individuals emigrating to countries that offer more competitive salaries and better working conditions. Thus human capital flight between 1999 and 2008–9, especially among the younger demographic, may have contributed to the French secular IQ decline, however the precise impact of the effect is difficult to determine.
