Flynn Effect Research Articles

The health gap: the challenge of an unequal world

The health gap: the challenge of an unequal world

A Strong Flynn Effect in South Korea during the Second Half of the Twentieth Century

Results from the standardization of the Wechsler Adult Intelligence Scale-4 (WAIS-IV) in South Korea show that when using British norms, average IQs are higher in Korea than in Britain among younger age groups, decline with age, and are lower than those in Britain among older age groups. These age differences are attributed to a strong Flynn effect in South Korea with IQs increasing at a rate of approximately 8.4 IQ points a decade from early 1940s to late 1980s birth cohorts. The increases were smallest for the Verbal Comprehension IQ and largest for the Processing Speed IQ. Key Words: WAIS-IV; Intelligence, Flynn effect, South Korea, UK

Flaws in Flynn Effect Research With the Wechsler Scales

Many Flynn effect (FE) studies compare scores across different editions of Wechsler’s IQ tests. When construct changes are introduced by the test developers in the new edition, however, the presumed generational effects are difficult to untangle from changes due to test content. To remove this confound, we use the same edition of Wechsler Intelligence Scale for Children–Fourth Edition (WISC-IV) across an 11-year period. Whereas previous research has reported the FE to be less than half the theoretical rate when comparing WISC-IV with Wechsler Intelligence Scale for Children–Fifth Edition (WISC-V), we find the rate of gain to be nearly identical to Flynn’s prediction when comparing only WISC-IV scores over the same time period. The FE is shown to vary significantly across the domains of cognitive ability, and thus changes to the construct coverage of the WISC-V Full Scale IQ (FSIQ) composite between editions significantly affect FE findings. Implications for future FE research are discussed.

It's getting bigger all the time: Estimating the Flynn effect from secular brain mass increases in Britain and Germany

Secular increases in brain mass over nearly a century have been noted for both males and females in the UK and Germany. It has been argued that such trends may be associated with the Flynn effect. The IQ gain predicted on the basis of these trends is 0.19 and 0.08 points per decade for UK, and 0.2 and 0.15 points per decade for German males and females respectively, indicating a small contribution to the Fullscale IQ trends in these countries (2.95% of the German decadal gain and 12.73% of the UK gain). There is also a sex difference in the rates of brain mass gain in both countries, favoring males. Temporal correlations between the secular trend in UK brain mass and European Flynn effects on Fullscale IQ, Crystallized, Fluid and Spatial abilities reveal correlations ranging from 0.751 in the case of Fluid ability to 0.761 in the case of Crystallized ability. The brain mass increase may be an imperfect proxy for changes in specific neuroanatomical structures important for IQ gains. Its small contribution to these gains is also consistent with the influence of other contributing factors. Increasing brain mass is predicted by the life history model of the Flynn effect as it suggests increased somatic effort allocation into bioenergetically expensive cortical real estate facilitating the development of specialized cognitive abilities.

A reversal of the Flynn effect for spatial perception in German-speaking countries: Evidence from a cross-temporal IRT-based meta-analysis (1977–2014)

Generational IQ changes (the Flynn effect) have been shown to be predominantly positive but differentiated according to IQ domains and countries. However, evidence from recent studies points towards a decrease of the Flynn effect globally or even a reversal in some countries. In the present meta-analysis, we show an inverse u-shaped trajectory of IQ test performance changes in a large number of samples (k=96; N=13,172) on a well-known test for spatial perception (the three-dimensional cubes test, 3DC) in German-speaking countries over 38years (1977–2014). Assessment of both item response theory-based measures as well as more standard measures of classical test theory showed initial increases and a subsequent decrease of performance when controlling for age, sample type (general population vs. mixed samples vs. university students) and sex. Our results suggest saturation and diminishing returns of IQ increasing factors (e.g., life history speed) whilst negative associations of IQ changes with psychometric g may have led to the observed IQ score decrease in more recent years.

Methodological Issues Associated with Studying the Flynn Effect: Exploratory and Confirmatory Efforts in the Past, Present, and Future

This essay, written by the guest editor, is an introduction to a special issue of the Journal of Intelligence devoted to methodological issues associated with the Flynn Effect. The essay evaluates past Flynn Effect research in terms of exploratory versus confirmatory efforts. Future research is also cast within this same framework. Finally, the four special issue papers are briefly reviewed, including comments on their own exploratory/confirmatory status.

The health gap: the challenge of an unequal world

The health gap: the challenge of an unequal world

Population Aging at Cross-Roads: Diverging Secular Trends in Average Cognitive Functioning and Physical Health in the Older Population of Germany.

This paper uses individual-level data from the German Socio-Economic Panel to model trends in population health in terms of cognition, physical fitness, and mental health between 2006 and 2012. The focus is on the population aged 50–90. We use a repeated population-based cross-sectional design. As outcome measures, we use SF-12 measures of physical and mental health and the Symbol-Digit Test (SDT) that captures cognitive processing speed. In line with previous research we find a highly significant Flynn effect on cognition; i.e., SDT scores are higher among those who were tested more recently (at the same age). This result holds for men and women, all age groups, and across all levels of education. While we observe a secular improvement in terms of cognitive functioning, at the same time, average physical and mental health has declined. The decline in average physical health is shown to be stronger for men than for women and found to be strongest for low-educated, young-old men aged 50–64: the decline over the 6-year interval in average physical health is estimated to amount to about 0.37 SD, whereas average fluid cognition improved by about 0.29 SD. This pattern of results at the population-level (trends in average population health) stands in interesting contrast to the positive association of physical health and cognitive functioning at the individual-level. The findings underscore the multi-dimensionality of health and the aging process.

Smarter every day: The deceleration of population ageing in terms of cognition

Cognitive decline correlates with age-associated health risks and has been shown to be a good predictor of future morbidity and mortality. Cognitive functioning can therefore be considered an important measure of differential ageing across cohorts and population groups. Here, we investigate if and why individuals aged 50+ born into more recent cohorts perform better in terms of cognition than their counterparts of the same age born into earlier cohorts (Flynn effect). Based on two waves of English and German survey data, we show that cognitive test scores of participants aged 50+ in the later wave are higher compared with those of participants aged 50+ in the earlier wave. The mean scores in the later wave correspond to the mean scores in the earlier wave obtained by participants who were on average 4–8years younger. The use of a repeat cross-sectional design overcomes potential bias from retest effects. We show for the first time that although compositional changes of the older population in terms of education partly explain the Flynn effect, the increasing use of modern technology (i.e., computers and mobile phones) in the first decade of the 2000s also contributes to its explanation.

Raven's is not a pure measure of general intelligence: Implications for g factor theory and the brief measurement of g

It has been claimed that Raven's Progressive Matrices is a pure indicator of general intelligence (g). Such a claim implies three observations: (1) Raven's has a remarkably high association with g; (2) Raven's does not share variance with a group-level factor; and (3) Raven's is associated with virtually no test specificity. The existing factor analytic research relevant to Raven's and g is very mixed, likely because of the variety of factor analytic techniques employed, as well as the small sample sizes upon which the analyses have been performed. Consequently, the purpose of this investigation was to estimate the association between Raven's and g, Raven's and a theoretically congruent group-level factor, and Raven's test specificity within the context of a bifactor model. Across several large samples, it was observed that Raven's (1) shared approximately 50% of its variance with g; (2) shared approximately 10% of its variance with a fluid intelligence group-level factor orthogonal to g; and (3) was associated with approximately 25% test specific reliable variance. Overall, the results are interpreted to suggest that Raven's is not a particularly remarkable test with respect to g. Potential implications relevant to the commonly articulated central role of Raven's in g factor theory, as well as the Flynn effect, are discussed. Finally, researchers are discouraged to include only Raven's in an investigation, if a valid estimate of g is sought. Instead, as just one example, a four-subtest combination from the Wechsler scales with a g validity coefficient of .93 and 14min administration time is suggested.

Using Score Equating and Measurement Invariance to Examine the Flynn Effect in the Wechsler Adult Intelligence Scale

The Flynn effect (FE; i.e., increase in mean IQ scores over time) is commonly viewed as reflecting population shifts in intelligence, despite the fact that most FE studies have not investigated the assumption of score comparability. Consequently, the extent to which these mean differences in IQ scores reflect population shifts in cognitive abilities versus changes in the instruments used to measure these abilities is unclear. In this study, we used modern psychometric tools to examine the FE. First, we equated raw scores for each common subtest to be on the same scale across instruments. This enabled the combination of scores from all three instruments into one of 13 age groups before converting raw scores into Z scores. Second, using age-based standardized scores for standardization samples, we examined measurement invariance across the second (revised), third, and fourth editions of the Wechsler Adult Intelligence Scale. Results indicate that while scores were equivalent across the third and fourth editions, they were not equivalent across the second and third editions. Results suggest that there is some evidence for an increase in intelligence, but also call into question many published FE findings as presuming the instruments' scores are invariant when this assumption is not warranted.

Estimating the strength of genetic selection against heritable g in a sample of 3520 Americans, sourced from MIDUS II

The relationship between IQ and completed fertility among a sample of 3520 Americans from MIDUS II (1960's birth cohorts) is examined using a common factor comprised of eight cognitive ability measures, in order to determine the rate of phenotypic IQ loss due to genetic selection. Negative correlations are present in both the male and female subsamples, and are associated with a predicted loss in heritable g (g.h) of −.262 points per decade, increasing to −1.072 points when the additive effect of mutation accumulation is considered. The ability–fertility associations showed Jensen effects at the level of the whole sample (.167), and also separately for each sex (.185 and .147 for the females and males respectively). The magnitude of the expected g.h loss in this cohort due to selection is comparable to that derived from a meta-analysis of disattenuated decadal g.h declines from eight US studies (−.44 points per decade; N=127,389). There is a Flynn effect in the US amounting to gains of 3.6 points per decade, which are concentrated on more environmentally plastic and specialized sources of ability variance (s.e) suggesting co-occurrent socio-ecological specialization with respect to narrower cognitive abilities in the present cohort.

Revisiting the Flynn Effect through 3D Immersive Virtual Reality (IVR)

The Flynn Effect, which identified the overwhelming improvement in IQ scores that took place during the second half of the 20th century, has now become known to all. After many attempts to explain the phenomenon, it is now widely accepted that nurture plays a major role in accelerating humanity's cognitive skills. This paper attempts to revisit these explanations by reflecting on a decade long of studies conducted in one Virtual Reality Laboratory aimed at better understanding the correlation between technology—more specifically, 3D Immersive Virtual Reality (3D IVR)—and the accelerated improvement in a variety of cognitive skills. These studies tested a few aspects of Flynn's social and cultural explanations. We examined, first, whether it is possible to generate an even greater acceleration in the enhancement of various abstract thinking skills. We asked whether it is possible to improve skills even among populations with congenital cognitive disabilities, and what is the most efficient way to accelerate the improvement. And most importantly—we examined whether it is possible to improve concrete thinking skills as well, which Flynn found not to have improved. The results of these studies cast solid doubt on Flynn's explanations, suggesting that advanced educational technologies, with their advanced interfaces, indeed generate an accelerated enhancement in a wide range of skills that the natural environment alone cannot account for.

A negative Flynn Effect in France, 1999 to 2008–9

The results of the French WAIS III (1999) and the French WAIS IV (2008–9) are compared based on a sample of 79 subjects aged between 30years and 63years who took both tests in 2008–2009. It is shown that between 1999 and 2008–9 the French Full Scale IQ declined by 3.8 points.

Assessing for Rising Visuospatial Ability of School Leavers

This paper investigated increasing visuospatial ability in three countries. Drawing on the Flynn Effect some researchers (Greenfield, 1998; Neisser, 1997) hypothesized that visuospatial ability may be increasing. I explored rising visuospatial abilities amongst school leavers in the UK, Australia and Nigeria. In one study Cocodia et al. (2003) found that exposure to new technology may be impacting on ability to carry out tasks that require high levels of visuospatial ability more efficiently. Results suggest that increasing visuospatial ability may be occurring due to a more visual environment and more access to multimedia. The core component of the present research paper was to investigate whether visuospatial ability is indeed rising as it is a feature of the human intelligence framework (Halpern & LaMay, 2000; Alias, Gray, & Black, 2001). Data analysis of examination results in specific subjects indicated that visuospatial abilities are rising. It was hypothesized that visuospatial ability is rising in industrialized nations due to more access to multimedia, and cognitive manipulation task in general.

One Century of Global IQ Gains

The Flynn effect (rising intelligence test performance in the general population over time and generations) varies enigmatically across countries and intelligence domains; its substantive meaning and causes remain elusive. This first formal meta-analysis on the topic revealed worldwide IQ gains across more than one century (1909–2013), based on 271 independent samples, totaling almost 4 million participants, from 31 countries. Key findings include that IQ gains vary according to domain (estimated 0.41, 0.30, 0.28, and 0.21 IQ points annually for fluid, spatial, full-scale, and crystallized IQ test performance, respectively), are stronger for adults than children, and have decreased in more recent decades. Altogether, these findings narrow down proposed theories and candidate factors presumably accounting for the Flynn effect. Factors associated with life history speed seem mainly responsible for the Flynn effect’s general trajectory, whereas favorable social multiplier effects and effects related to economic prosperity appear to be responsible for observed differences of the Flynn effect across intelligence domains.

By their words ye shall know them: Evidence of genetic selection against general intelligence and concurrent environmental enrichment in vocabulary usage since the mid 19th century.

It has been theorized that declines in general intelligence (g) due to genetic selection stemming from the inverse association between completed fertility and IQ and the Flynn effect co-occur, with the effects of the latter being concentrated on less heritable non-g sources of intelligence variance. Evidence for this comes from the observation that 19th century populations were more intellectually productive, and also exhibited faster simple reaction times than modern ones, suggesting greater information-processing ability and therefore higher g. This co-occurrence model is tested via examination of historical changes in the utilization frequencies of words from the highly g-loaded WORDSUM test across 5.9 million texts spanning the period 1850–2005. Consistent with predictions, words with higher difficulties (δ parameters from Item Response Theory) and stronger negative correlations between pass rates and completed fertility declined in use over time whereas less difficult and less strongly selected words, increased in use over time, consistent with a Flynn effect stemming in part from the vocabulary enriching effects of increases in population literacy. These findings persisted when explicitly controlled for word age, changing literacy rates and temporal autocorrelation. These trends constitute compelling evidence for the co-occurrence model.

Rising–falling mercury pollution causing the rising–falling IQ of the Lynn–Flynn effect, as predicted by the antiinnatia theory of autism and IQ

A fundamental principle of the antiinnatia theory of autism and IQ is that the same factors (genetic and environmental) which in extreme high levels cause autism, in more modal levels cause increased IQ. And the factors which generally cause raised IQ, in extreme levels cause autism. The antiinnatia theory further proposed that molecules randomly part-time binding to DNA and thereby reducing gene-expression would cause autism (and in less high levels cause raised IQ). Studies have found that mercury binds dose-dependently to DNA thereby reducing gene-expression, and thus the theory predicts that mercury pollution would cause raised IQ (such as the Flynn effect). This appears contrary to the standard assumption that mercury pollution causes decrements of IQ. In this study, data from the Upper Fremont glacier finds considerable overall correspondence between changes of mercury pollution and changes of IQ. In respect of both mercury and IQ there was roughly-speaking 100years of increase followed by 15years of decrease in at least five countries. But mercury pollution is likely to be causing serious harms other than decrements of population averages of IQ.

The cognitive impact of the education revolution: A possible cause of the Flynn Effect on population IQ

The phenomenon of rising IQ scores in high-income nations over the 20th century, known as the Flynn Effect, indicates historical increase in mental abilities related to planning, organization, working memory, integration of experience, spatial reasoning, unique problem-solving, and skills for goal-directed behaviors. Given prior research on the impact of formal education on IQ, a three-tiered hypothesis positing that schooling, and its expansion and intensification over the education revolution, is one likely cause of the Flynn Effect is tested in three studies. First, a neuroimaging experiment with children finds that neuromaturation is shaped by common activities in school, such as numeracy, and share a common neural substrate with fluid IQ abilities. Second, a field study with adults from insolated agrarian communities finds that variable exposure to schooling is associated with related variation in the mental abilities. Third, a historical–institutional analysis of the cognitive requirements of American mathematics curriculum finds a growing cognitive demand for birth cohorts from later in the 20th century. These findings suggest a consilience of evidence about the impact of mass education on the Flynn Effect and are discussed in light of the g-factor paradigm, cognition, and the Bell Curve debate.

Matrices Progresivas de Raven: efecto Flynn y actualización de baremos

Este trabajo presenta los resultados obtenidos en la construcción de normas válidas y actualizadas del Test de Matrices Progresivas de Raven, Escala General, para la ciudad de La Plata, Argentina; y realiza una comparación con las normas obtenidas en 1964 y 2000 a fin de observar la tendencia de los puntajes. Se seleccionó una muestra de 1001 estudiantes de ambos sexos y provenientes de distintos establecimientos de educación secundaria, con edades comprendidas entre los 13 y 18 años. El instrumento fue administrado de manera colectiva, en grupos-clase, con presencia del examinador, sin límite de tiempo para su ejecución, de manera tal que permitiera evaluar la capacidad intelectual sin la intervención de la velocidad en la tarea. Los resultados obtenidos se analizaron dividiéndolos en tres grupos por edad (i.e., 13-14 años, 15-16 años, 17-18 años), y se compararon con los baremos de 1964 y 2000. Se observó un leve descenso de los puntajes directos necesarios para alcanzar el rendimiento promedio, respecto de las puntuaciones obtenidas en la tipificación del año 2000, en la que se constató el efecto Flynn respecto de las normas de 1964. Esta tendencia está en consonancia con investigaciones recientes realizadas en otros países, que muestran un amesetamiento de los puntajes. Un segundo aspecto observado, fue que a medida que aumenta la edad de los sujetos, el rendimiento es mejor. La variabilidad de los puntajes es similar entre los tres grupos de edad analizados.