"The negative Flynn Effect: A systematic literature review", Dutton et al 2016:
"The Flynn Effect (rising performance on intelligence tests in the general population over time) is now an established phenomenon in many developed and less developed countries. Recently, evidence has begun to amass that the Flynn Effect has gone into reverse; the so-called ‘Negative Flynn Effect.’ In this study, we present a systematic literature review, conducted in order to discover in precisely how many countries this reverse phenomenon has been uncovered. Using strict criteria regarding quality of the sample and the study, we found nine studies reporting negative Flynn Effects in seven countries. We also discuss several possible explanations for the negative Flynn Effect as an attempt to understand its most probable causes.
The nine articles included, draw upon the following tests:
(1) Sundet et al. (2004) used the General Ability Test, an IQ test developed by the Norwegian army in 1954. It is composed of Words, Numbers and Shapes and conscripts are given a GA (General Ability) score, which corresponds to an IQ score.
(2) Woodley and Meisenberg's (2013) meta-analysis of tests of Dutch adults used the GATB = General Aptitude Test Battery. This measures 9 different ‘aptitudes’ among which are verbal aptitude, numerical aptitude and spatial aptitude.
(3) Teasdale and Owen's (2008) study drew upon the Borge Prien's Prove, which is an IQ test used by the Danish army on recruits since 1961. It is comprised of logical, verbal, numerical and spatial reasoning tests.
(4) Shayer and Ginsburg's (2007, 2009) studies drew upon the Piagetian test: An IQ test developed for children. Piaget's theory focuses on interviewing the subjects to discover why they answered in a particular way.
(5) Dutton and Lynn's (2013) study drew upon annual average results of the Finnish Peruskoe, which literally translates as ‘Basic test.’ This is an IQ test developed by the Finnish army composed of Numbers, Words and Shapes tests. These results were reported in Koivunen (2007) up to 2001, a thesis which was sent to them by a Finnish army researcher, as well as in correspondence with the same Finnish army researcher for 2008–9.
(6) Korgesaar's (2013) Estonian study drew upon the Raven Standard Progressive Matrices (SPM) test, which is a widely-accepted test of general intelligence and, as such, the study is within our inclusion criteria.
(7) (7) Dutton and Lynn (2015) drew upon the French WAIS (Wechsler Adult Intelligence Test) IV manual.
From Table 1 it can be seen that in the majority of the studies the decline ranges between 0.38 and 4.30 IQ points per decade. The Estonian study seems to be somewhat of an outlier with a decline of 8.4 IQ points per decade. Taking the un-weighted average of all the studies, the mean decline per decade in the studies would be 3.18 points. When excluding the rather high value of Estonia, the average decline in the remaining seven studies becomes 2.44 IQ points per decade.
Focussing on the Nordic data, Sundet (correspondence quoted in Dutton, 2014, p.243) has noted that: “Men from (South) Asian and African countries have around 5–6 IQ points lower than non-immigrants. Yet, they seem to comprise no more than around 2–3% of the conscripts in this period. If there would be any effect then this would deflate the total mean IQ by around a maximum of 0.1–0.2 IQ points.” As such, it simply cannot fully explain the decline. Also, conscript data from Finland is particularly important in assessing the immigration hypothesis. Finland did not experience any significant third world immigration until around 1992 (see Dutton & Lynn, 2013). However, the conscripts in 1997 would have been mainly born in 1978 when the non-white population of Finland was vanishingly small.
Despite the limitations outlined above and the small N (= 7) for country level, we decided to calculate the correlation between the IQ decline per decade and average immigration between 1950 and 2015 (Migration Policy, 2016). When including all countries in the review, the correlation was virtually zero (r(7) = 0.033, p = 0.94). However, it has to be noted that Estonia did not only appear to be an outlier regarding the IQ decline, but also regarding immigration, because it was the only country that showed negative immigration numbers. When conducting the calculations again, but this time excluding Estonia, the correlation became r(6) = 0.802 and reached marginal significance (p = 0.055). Nevertheless, we have already noted that, based on the percentage of immigrants in the most reliable samples, immigration is unlikely to have a large influence. Accordingly, this association may be underpinned by a factor, which underlies both dysgenics and high immigration levels, such as degree of societal development or putative amount of time since industrialization.
something precipitated, possibly, by living in more educated society, as argued by Flynn (2012). He argues that modern society makes us increasingly look at the world through ‘scientific spectacles’ and, accordingly, examine it analytically, boosting performance IQ, especially on similarities. As this is ultimately underpinned by intelligence, it would have a genotypic limit and if genotypic intelligence were declining then the imperfect nature of the IQ test as a measure of intelligence would mask this, but only up to the genotypic limit. Once this limit was reached, any genotypic decline in IQ would become visible on the IQ tests. As mentioned above, this is known as the Co-occurrence Model. It is possible that this is what has happened because dysgenic fertility - a negative association between intelligence and numbers of children - has been observed in Denmark, Sweden, Finland, and a number of other countries reviewed in Lynn (2011). Indeed, if Flynn's ‘scientific spectacles’ explanation is accurate then we would expect to see, prior to an overall negative Flynn Effect, a negative effect on verbal and mathematical IQ concomitant with a positive effect on other parts of the test. This is, indeed, what we see in the studies we excluded. Khaleefa, Sulman, and Lynn (2009) found that Sudanese Full-scale IQ increased 2.05 points per decade between 1987 and 2007, but Verbal IQ decreased by 1.65 points over the period. Colom, Andres-Pueyo, and Juan-Espinosa (1998) reported a decline in Spanish verbal reasoning (male and female −0.3) and mathematical reasoning (male − 2.4; female − 2.1) between 1979 and 1995 but a rise on abstract reasoning (and also Ravens) sufficient to create an overall Flynn Effect.
Besides such differential effects on subtests, we would also expect to see a slowing down of the Flynn Effect before it ultimately ceased, because the Flynn Effect itself would be partly g-loaded (with g in decline) and there would be a limit to the extent to which the environment can raise IQ scores. The meta-analysis of the Flynn Effect by Pietschnig and Voracek (2015) does indeed show that IQ gains since the 1980s had considerably slowed down. The gains were also increasingly non-linear in this period."