Is the Flynn effect on g?: A meta-analysis

Black/White differences in mean IQ have been clearly shown to strongly correlate with g loadings, so large group differences on subtests of high cognitive complexity and small group differences on subtests of low cognitive complexity. IQ scores have been increasing over the last half century, a phenomenon known as the Flynn effect. Flynn effect gains are predominantly driven by environmental factors. Might these factors also be responsible for group differences in intelligence? The empirical studies on whether the pattern of Flynn effect gains is the same as the pattern of group differences yield conflicting findings. A psychometric meta-analysis on all studies with seven or more subtests reporting correlations between g loadings and standardized score gains was carried out, based on 5 papers, yielding 11 data points (total N = 16,663). It yielded a true correlation of − .38, and none of the variance between the studies could be attributed to moderators. It appears that the Flynn effect and group differences have different causes. Suggestions for future research are discussed.     

Establishing an association between the Flynn effect and ability differentiation

The relationship between the Flynn effect and ability differentiation is investigated in a reanalysis of published data on Estonian student cohorts tested in 1933/36, 1997/98 and 2006 on the National Intelligence Test (Must, te Nijenhuis, Must, & van Vianen, 2009). To determine whether there was a relationship we computed the vector correlation between the Flynn effects (d) and the change in the g loading (Δg) between measurement occasions for each of the 10 NIT subtests and for each of the seven cohort comparisons, giving a total N of 70 effect sizes. The association between d and Δg was robustly negative (indicating that the Flynn effects were negatively associated with changes in the g loading of subtests) for all cohort comparisons, with values of r ranging from −.100 to −.461 (N = 10). When all effect sizes were analyzed together, the vector correlation was found to be −.281 (p ? .05, N = 70). This indicates a significant association between the Flynn effect and ability differentiation. Possible causes of this association are discussed.     

An item-level examination of the Flynn effect on the National Intelligence Test in Estonia

This study examined the Flynn effect (FE; i.e., the rise in IQ scores over time) in Estonia using the Estonian version of the National Intelligence Tests (NIT;  and ). Using secondary data from two cohorts (1934, n = 890 and 2006, n = 913) of students, we analyzed the NIT's subtests using item response theory (IRT). For each subtest, we first examined invariance in all the items and then linked the latent variable (θ) scores between the two cohorts using the invariant items. The results showed that there was a FE in θ for all subtests except one, although there was much variability in the FE magnitude, ranging from an effect size of 0.24 (3.60 IQ points) to 1.05 (15.75 IQ points). In addition, this study showed there was a decrease in the variability of θ for all the subtests, although only two of the subtests showed large decreases (approximately .50 standard deviations). Last, the subtests' precision of measuring θ was very similar at both time points.     

A Jensen effect on dysgenic fertility: An analysis involving the National Longitudinal Survey of Youth

In this study we attempt to determine whether dysgenic fertility is associated with the Jensen effect. This is investigated with respect to a US population representative sample of 8110 individuals from the National Longitudinal Survey of Youth for whom there exists complete data on IQ and fertility. In addition to the general sample, the sample was also broken out by race and sex so as to examine whether or not the Jensen effect manifested amongst different sub-populations. The method of correlated vectors revealed significant Jensen effects in five of the seven samples, and in all cases the effect was in a direction indicating that subtests with higher g-loadings were associated with larger dysgenic fertility gradients. The magnitude of the difference between Spearman’s ρ and Pearson’s r was non-significant in all cases, suggesting that biasing factors were minimally influencing the result. This finding suggests that dysgenesis occurs on the ‘genetic g’ at the heart of the Jensen effect nexus, unlike the Flynn effect, which is ‘hollow’ with respect to g. Finally, the finding is discussed in the context of two converging lines of evidence indicating that genotypic IQ or ‘genetic g’ really has been declining over the last century.     

Four successful tests of the Cognitive Differentiation–Integration Effort hypothesis

The Cognitive Differentiation–Integration Effort (CD–IE) hypothesis predicts that the dimension of life history speed (K) regulates the strength of the correlation among cognitive abilities, such that individuals with higher K exhibit more weakly integrated abilities than those with lower K. It is predicted that this effect takes place independently of the level of g owing to the absence of an individual differences level correlation between K and g. CD–IE was examined using two student samples: (1) an all female sample (N = 121), using the ALHB as a measure of K and the two SILS subtests of g; and (2) a combined male and female sample (N = 346), using a shorter three-indicator (“Trifecta”) measure of K, a general creativity measure comprised of two subscales (writing and drawing “creative performance”), and the APM-18 measure of fluid cognition. A third, population-representative sample was obtained from the NLSY (N = 11,907). A K-Factor was constructed from convergent measures of subjective well-being, sociability, interpersonal trust, internal locus of control, and delay of gratification, and a g-factor was constructed from the 10 subscales of the ASVAB. A fourth sample, addressing the question of ethnic differences was collected encompassing eight different ethnic groups with a combined 107 specific ability correlations with g. An aggregate K-Factor was constructed for this sample based on convergent population-level indicators of longevity, total fertility rates and infant mortality. Utilizing the Continuous Parameter Estimation Model, in student sample 1 a significant CD–IE effect was found on the SILS Abstract subtest (β = − .215), but not on the SILS Verbal subtest (β = .069). In student sample 2, CD–IE was observed on the general creativity measure (β = − .127), but not on the fluid cognitive ability measure (β = − .057). Significant effects were also observed on both the written and drawing creative output subscales (β = − .189 and − .183 respectively). In sample 3 (the NLSY), generally statistically significant but small-magnitude CD–IE effects were observed among all 10 ASVAB subtests (mean effect size β = − .032). In sample four, a near-significant CD–IE effect was detected (β = − .167). Controlling for subtest skew reduces the mean effect sizes across individual differences samples (β = − .071 in the student samples, − .027 in the NLSY), but boosted it to significance in the ethnic differences sample (β = − .179). Controlling for the skew of residuals reversed the signs of the CD–IE effects on the ASVAB Words and Comprehension subscales, and also on the SILS Verbal subscale, but amplified the magnitudes of the mean effects in the student and NLSY samples (β = − .036 and − .131), while reducing the effect size slightly in the ethnic-differences sample (β = − .172). In the individual differences samples, these effects were demonstrated to be unconfounded with sex of respondent and also unrelated to the Jensen effect. The apparent independence of the effect from both level of g and subtest g-loading suggests intriguing commonalities with the Lynn–Flynn effect.     

The Flynn effect in South Africa

This is a study of secular score gains in South Africa. The findings are based on representative samples from datasets utilized in norm studies of popular mainstream intelligence batteries such as the WAIS as well as widely used test batteries which were locally developed and normed in South Africa. Flynn effects were computed in three ways. First, studies where two different groups take the same test, with several years in between, using representative or comparable samples were used. Second, studies where the same group takes two different test batteries at a specific time were used. Third, the score differences between English- and Afrikaans-speaking Whites in South Africa in the 20th century were compared. The Flynn effect in White groups in South Africa is somewhat smaller than the Flynn effect in Western, industrialized countries (total N = 6534), and the Flynn effect in Indian groups is substantially smaller (total N = 682). Non-verbal IQ scores surpassed increases in verbal IQ scores. The findings from English- and Afrikaans-speaking Whites evidence a leveling out of differences in score gains over the 20th century (total N = 79,310). A meta-regression analysis showed no clear support for the moderators a) method used for computing the Flynn effect gain, b) type of test battery, c) time span, d) quality of the sample, and e) average age of sample.     

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.     

Changes in test-taking patterns over time

The current study aims to investigate the relationship between right, wrong and missing answers to cognitive test items (test-taking patterns) in the context of the Flynn Effect (FE). We compare two cohorts of Estonian students (1933/36, n = 890; 2006, n = 913) using an Estonian adaptation of the National Intelligence Tests and document three simultaneous trends: fewer missing answers (− 1 Cohen's d averaged over subtests), and a rise in the number of right and wrong answers to the subtests (average ds of .86 and .30, respectively). In the Arithmetical Reasoning and Vocabulary subtests, adjustments for false-positive answers (the number of right minus the number of wrong answers) reduced the size of the Flynn Effect by half. These subtests were supposed to be high g-loading subtests. Our conclusion is that rapid guessing has risen over time and influenced tests scores more strongly over the years. The FE is partly explained by changes in test-taking behavior over time.     

Ability rise in NAEP and narrowing ethnic gaps?

US National Assessment of Educational Progress (NAEP) results from 1971 to 2008 enable four different effects to be distinguished: Cohort rise effects, gap-narrowing between ethnic groups, trends due to demographic changes in by NAEP listed or not listed ethnic groups. NAEP means and percentiles in reading and mathematics were transformed to conventional IQs and SDs. The total increase from 1971 to 2008 was in the scale of 4.34 IQ points (dec = 1.17 IQ per decade). The ability distribution became more homogenous (down from SD = 15.00 in 1971 to SD = 13.56 in 2008). Increases were larger for younger students (9-year olds: 2.02 IQ per decade; 13-year olds: 1.20; 17-year olds: 0.30); larger at the lower ability level (10th percentile dec = 1.79 vs. 90th percentile dec = 1.03). The largest increase was for Blacks (Whites dec = 1.29 IQ, Hispanics 2.27, Blacks 3.04). White–Hispanic-differences were reduced from 11.59 to 8.46 IQ, White–Black from 16.33 to 9.94 IQ. If the racial composition of the population had not changed, the mean gain for the 17-year-old group would have been 2.47 IQ points higher. Had the gap between Whites and the two other groups not narrowed, the mean gain would have been 1.70 IQ points lower. Demographic change has accounted for a loss of 2.47 IQ points and according to cognitive human capital theory $2001 GDP per capita per year, but total ethnic gap-narrowing has provided a gain of $1377.     

The Flynn effect,group differences,and g loadings

Flynn effect gains are predominantly driven by environmental factors. Might these factors also be responsible for group differences in intelligence? Group differences in intelligence have been clearly shown to strongly correlate with g loadings. The empirical studies on whether the pattern of Flynn effect gains is the same as the pattern of group differences yield conflicting findings. We present new evidence on the topic using a number of datasets from the US and the Netherlands. Score gains and g loadings showed a small negative average correlation. The general picture is now that there is a small, negative correlation between g loadings and Flynn effect gains. It appears that the Flynn effect and group differences have different causes.     

Item-response theory modeling of IQ gains (the Flynn effect) on crystallized intelligence: Rodgers' hypothesis yes,Brand's hypothesis perhaps

Potential explanations for generational intelligence test score gains continue to be subject to intense debate and scrutiny in the scientific community. However, the explanatory value of some of the proposed causes remains difficult to determine, since only little empirical evidence is available. To clarify the role of two scarcely investigated theories accounting for the Flynn effect, this study set out to examine the role of changing test-taking behavior (Brand's hypothesis) and of a narrowing of the IQ ability distribution (Rodgers' hypothesis). Archival records of crystallized intelligence test performance over a time-span of 17 years of a large number of psychiatric inpatients and outpatients in Austria were investigated (N = 5445; 1978–94). This sample was particularly suitable to investigate our hypotheses since participants were under no pressure to perform which makes observed changes in test taking behavior attributable to personal style and ability rather than differential performance in pressure situations. Analytical approaches of both classical test theory and item response theory (IRT) yielded gains of 1.0 to 2.4 IQ points per decade. Test-taking behavior indicative of guessing and decreasing population IQ variability appeared to contribute both to IQ test score gains. IRT-based analyses showed that gains were largely preserved when controlling for highest educational qualification, while the test instrument showed measurement invariance between cohorts. However, IRT-based results also suggested that changes in test-taking behavior might not necessarily reflect increased guessing, but item drift instead. In all, this evidence emphasizes better performance of individuals of the lower tail of the IQ ability distribution in more recent years as one important contributing factor for generational IQ test score gains.     

Personality and political orientation: Meta-analysis and test of a Threat-Constraint Model

We synthesized and meta-analyzed 73 studies (N = 71,895) examining the associations between Big-Five personality and single-item self-placement measures of political orientation. Openness to Experience (r = −.18) and Conscientiousness (r = .10) were significantly but weakly correlated with political conservatism. The weak Openness-political orientation link was moderated by systemic threat and uncertainty (indexed by nation-wide homicide and unemployment). We propose a Threat-Constraint Model explaining this previously undetected Person × Situation interaction. The model shows that there was a moderately-sized negative correlation between Openness and political conservatism when systemic threat was low (r = −.422) but that this association was negligible at only moderate levels of threat (r = −.066). These findings highlight the economic and societal constraints of personality-political ideology associations.     

Were the Victorians cleverer than us? The decline in general intelligence estimated from a meta-analysis of the slowing of simple reaction time

The Victorian era was marked by an explosion of innovation and genius, per capita rates of which appear to have declined subsequently. The presence of dysgenic fertility for IQ amongst Western nations, starting in the 19th century, suggests that these trends might be related to declining IQ. This is because high-IQ people are more productive and more creative. We tested the hypothesis that the Victorians were cleverer than modern populations, using high-quality instruments, namely measures of simple visual reaction time in a meta-analytic study. Simple reaction time measures correlate substantially with measures of general intelligence (g) and are considered elementary measures of cognition. In this study we used the data on the secular slowing of simple reaction time described in a meta-analysis of 14 age-matched studies from Western countries conducted between 1889 and 2004 to estimate the decline in g that may have resulted from the presence of dysgenic fertility. Using psychometric meta-analysis we computed the true correlation between simple reaction time and g, yielding a decline of − 1.16 IQ points per decade or − 13.35 IQ points since Victorian times. These findings strongly indicate that with respect to g the Victorians were substantially cleverer than modern Western populations.     

IQ, skin color, crime, HIV/AIDS, and income in 50 U.S. states

In 50 U.S. states, we found a positive manifold across 11 measures including IQ, skin color, birth rate, infant mortality, life expectancy, HIV/AIDS, violent crime, and state income with the first principal component accounting for 33% of the variance (median factor loading = .34). The correlation with a composite of total violent crime was higher with skin color (r = .55), a more biologically influenced variable than with GDP (r = −.17), a more culturally influenced variable. These results corroborate and extend those found at the international level using INTERPOL crime statistics and at the county, provincial, and state levels within countries using local statistics. We interpret the cross-cultural consistency from an evolutionary life history perspective in which hierarchically organized traits culminate in a single, heritable, super-factor. Traits need to be genetically organized to meet the trials of life—survival, growth, and reproduction. We discuss brain size and the g nexus as central to understand individual and group differences and we highlight melanin and skin color as a potentially important new life history variable.     

Antecedents and consequences of retirement planning and decision-making: A meta-analysis and model

In this study, meta-analytic procedures were used to examine the relationships between retirement planning, retirement decision and their antecedent and consequences. Our review of the literature generated 341 independent samples obtained from 99 primary studies with 188,222 participants. A small effect size (ES) for antecedents of retirement planning (poor health, negative working conditions and positive attitudes toward retirement) was obtained (ranging from r = .05 to r = .19), whereas a medium ES was obtained for work involvement and job satisfaction (r = −.31 and r = −.34). Regarding retirement decision, lower effect sizes were obtained. Effect sizes for the relationships with consequences were medium for retirement planning and bridge employment (r = .28), for retirement decision-volunteer work (r = .26), and for retirement decision-retirement satisfaction (r = .26). Structural equation analysis using the pooled correlation matrix allowed us to test a more complex model. Potential moderator variables were examined, and it was found that they explained only a small percentage of variability of primary studies. Results are discussed, and theoretical and empirical implications are suggested.     

Comparability of IQ scores over time

This study investigates the comparability of IQ scores. Three cohorts (1933/36, 1997/98, 2006) of Estonian students (N = 2173) are compared using the Estonian National Intelligence Test. After 72 years the secular rise of the IQ test scores is.79 SD. The mean .16 SD increase in the last 8 years suggests a rapid increase of the Flynn Effect (FE) in Estonia. The measurement is not strictly invariant, which means that the IQ scores of different cohorts are not directly comparable. Less than perfect comparability of test scores is caused by at least two factors: time between measurements and societal/educational changes between cohorts. As was to be expected, the meaning of subtests and the meaning of the g score have changed over time.     

Positive Traits Linked to Less Pain through Lower Pain Catastrophizing

The present study examined the association between positive traits, pain catastrophizing, and pain perceptions. We hypothesized that pain catastrophizing would mediate the relationship between positive traits and pain. First, participants (n = 114) completed the Trait Hope Scale, the Life Orientation Test-Revised, and the Pain Catastrophizing Scale. Participants then completed the experimental pain stimulus, a cold pressor task, by submerging their hand in a circulating water bath (0 °C) for as long as tolerable. Immediately following the task, participants completed the Short-Form McGill Pain Questionnaire (MPQ-SF). Pearson correlation found associations between hope and pain catastrophizing (r = −.41, p < .01) and MPQ-SF scores (r = −.20, p < .05). Optimism was significantly associated with pain catastrophizing (r = −.44, p < .01) and MPQ-SF scores (r = −.19, p < .05). Bootstrapping, a non-parametric resampling procedure, tested for mediation and supported our hypothesis that pain catastrophizing mediated the relationship between positive traits and MPQ-SF pain report. To our knowledge, this investigation is the first to establish that the protective link between positive traits and experimental pain operates through lower pain catastrophizing.     

White–black differences in g and non-g effects for the SAT and ACT

This research examined g and non-g effects for the SAT and ACT for whites and blacks. SAT scores, ACT scores, and college GPAs were obtained from the National Longitudinal Survey of Youth. g was estimated using the Armed Services Vocational Aptitude Battery. Results indicated that (a) the g loadings of SAT and ACT composite scores were lower for whites than blacks, (b) group differences in the g loadings were related to the math subtests of the SAT and ACT, and (c) non-g variance accounted for surprisingly large percentages of SAT–GPA and ACT–GPA relations (range = 37–67%). The findings are discussed in terms of Spearman’s Law of Diminishing Returns.     

Intelligence and physical attractiveness

This brief research note aims to estimate the magnitude of the association between general intelligence and physical attractiveness with large nationally representative samples from two nations. In the United Kingdom, attractive children are more intelligent by 12.4 IQ points (r = .381), whereas in the United States, the correlation between intelligence and physical attractiveness is somewhat smaller (r = .126). The association between intelligence and physical attractiveness is stronger among men than among women in both nations. The association remains significant net of a large number of control variables for social class, body size, and health.     

An increase of intelligence in China 1986–2012

The Flynn effect has been widely researched in Western and European nations, while it has been comparatively understudied in Asian countries. This study examines possible Flynn effects in China from 1985 to 86 and to 2011–12. Results are reported for an IQ increase among 12 year olds on the Full Scale IQ WISC-R (Wechsler Intelligence Scale for Children-Revised) of 6.19 IQ points, a gain on the Performance IQ of 6.55 IQ points, and a gain on the Verbal IQ of 1.91 IQ points.