The rise of national intelligence: Evidence from Britain, Japan and the U.S.A

Cognitive performance trends among European older adults: exploring variations across cohorts, gender, and educational levels (2007-2017)

BACKGROUND

This study explores recent cohort trends in cognitive performance among older Europeans from 2007 to 2017, addressing three key questions: (1) Did cognitive performance improve universally and across the performance distribution during this period? (2) Did these improvements occur across educational levels and for both men and women? (3) Can established risk factors explain these performance gains?

METHODS

Using data from the Survey of Health, Ageing and Retirement in Europe (SHARE) across 12 European countries, we assessed immediate recall, delayed recall, and verbal fluency in individuals aged 60 to 94 in both 2007 and 2017 (n = 32 773). Differences between the two time points were estimated with linear mixed effects regression models and quantile regression.

RESULTS

Cognitive performance improved in all age groups, across educational levels, and for both men and women between 2007 and 2017. Notably, improvements were more pronounced at the upper end of the performance distribution for delayed recall and verbal fluency. Education explained approximately 20% of the observed improvements. Risk factors did not explain the observed improvements.

CONCLUSIONS

European cohorts of both younger-old and older adults continue to exhibit improvements in cognitive performance. Variation in the size of the cohort improvements across the performance distributions in delayed recall and in verbal fluency may contribute to growing inequalities in cognitive outcomes. Future research should further investigate the potential heterogeneity in cognitive performance gains.

TRIAL REGISTRATION

Not applicable.

Neurodiversity and Intelligence: Evaluating the Flynn Effect in Children with Autism Spectrum Disorder

The Flynn Effect (FE) among child and adolescent populations indicates that intelligence scores improve by about three points per decade. Using nine years of data from the National Database for Autism Research, this study examined whether general intelligence changed significantly for nine cohorts with autism spectrum disorder (ASD; N = 671). Analyses demonstrated a downward trend such that Cohen's d from 1998 to 2006 was - 0.27. The mean IQ is 92.74 for years 1-3, 91.54 for years 4-6, and 87.34 for years 7-9, indicating a reverse FE of 5.4 points per decade. A linear regression revealed a significant negative FE comparable to the positive effect of age on IQ among those with ASD. Implications for research, practice, and law are discussed.

Factors Associated with Lower Cognitive Performance Scores Among Older Japanese Men in Hawaii and Japan

BACKGROUND

Few studies have compared factors related to cognitive function among people with similar genetic backgrounds but different lifestyles.

OBJECTIVE

We aimed to identify factors related to lower cognitive scores among older Japanese men in two genetically similar cohorts exposed to different lifestyle factors.

METHODS

This cross-sectional study of community-dwelling Japanese men aged 71-81 years included 2,628 men enrolled in the Kuakini Honolulu-Asia Aging Study based in Hawaii and 349 men in the Shiga Epidemiological Study of Subclinical Atherosclerosis based in Japan. We compared participant performance through Cognitive Abilities Screening Instrument (CASI) assessment in Hawaii (1991-1993) and Japan (2009-2014). Factors related to low cognitive scores (history of cardiovascular disease, cardiometabolic factors, and lifestyle factors) were identified with questionnaires and measurements. Multivariable logistic regression analysis was used to calculate the adjusted odds ratios (ORs) of a low (< 82) CASI score based on different factors.

RESULTS

CASI scores were lower in Hawaii than in Japan [21.2%(n = 556) versus 12.3%(n = 43), p < 0.001], though this was not significant when adjusted for age and educational attainment (Hawaii 20.3%versus Japan 17.9%, p = 0.328). History of stroke (OR = 1.65, 95%confidence interval = 1.19-2.29) was positively associated with low cognitive scores in Hawaii. Body mass index ≥25 kg/m2 tended to be associated with low cognitive scores in Japan; there was a significant interaction between the cohorts.

CONCLUSION

Cognitive scores differences between cohorts were mostly explained by differences in educational attainment. Conversely, cardiovascular diseases and cardiometabolic factors differentially impacted cognitive scores among genetically similar older men exposed to different lifestyle factors.

One Century of Global IQ Gains: A Formal Meta-Analysis of the Flynn Effect (1909-2013)

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.

Further Evidence on the Cognitive Abilities of the Japanese: Data from the WPPSI

The structure of abilities of Japanese children is analysed in terms of the Burt-Vernon hierarchical model of intelligence. The data are derived from the Japanese standardisation of the Wechsler Preschool and Primary Scale for Intelligence. It is found that Japanese children do not differ significantly from white American children on Spearman's g, are significantly inferior on the group verbal factor and superior on the group perceptual factor. On the primary abilities, Japanese children are inferior on verbal comprehension, not significantly different on perceptual speed, and superior on number and spatial ability. It is suggested-that this pattern of Japanese cognitive strengths and weaknesses helps to clarify a number of conflicting findings on Japanese intelligence.

Reaction Times and Intelligence in Chinese and British Children

239 British and 118 Chinese Hong Kong nine-year-old children, each representative for intelligence of Britain and Hong Kong, were tested on the Standard Progressive Matrices and on reaction times. The reaction time apparatus measured simple and complex reaction times proper (i.e., decision times), movement times, and variabilities. The results showed that all the reaction time measures were associated with intelligence and that Hong Kong children had a higher mean IQ and faster reaction times than British children. This suggests that the difference in mean IQ between Hong Kong and British children has a neurological basis. However, the British children showed faster movement times and lower variabilities, contrary to expectation. This suggests independent neurological processes may underlie reaction times, movement times, and variabilities.

A New Estimate of the IQ in Estonia

The Standard Progressive Matrices was standardized in Estonia in 2001 on a sample of 1,835 7- to 11-yr.-olds. The mean IQ of the Estonian sample was estimated at 98 in relation to a British IQ of 100 and 99 based on the combined results for two studies.

Does the Flynn Effect Differ by IQ Level in Samples of Students Classified as Learning Disabled?

This research examined scores from two learning-disabled (LD) samples for evidence of the Flynn Effect (FE; Flynn, 1999) to determine (a) whether the FE was evident, and (b) if the magnitude of the FE differed on IQ scores at varying levels of intelligence. Sample 1 consisted of 40 children who were administered the Woodcock-Johnson Tests of Cognitive Ability-Revised (WJ-R Cog) and the Woodcock-Johnson Tests of Cognitive Ability-Ill (WJ-III Cog) approximately 8 weeks apart. Sample 2 consisted of triennial test data for 169 students who were tested once with the Wechsler Intelligence Scale for Children-Revised (WISC-R) and 3 years later with the Wechsler Intelligence Scale for Children-Third Edition (WISC-III). After an initial analysis for the overall FE, Samples 1 and 2 were each divided into IQ level groups (e.g., 91-105) and analyzed accordingly. Results for Sample 1 (W-J) indicated that the 2+ point observed IQ change was not significant for this relatively small sample, although it appeared to be consistent with the direction and degree predicted by the FE (Flynn, 1984). Results for Sample 2 (WISC) indicated a significant IQ change consistent with the FE. Neither sample exhibited statistically significant differences for FE by IQ level. However, consistent with previous research, observed differences increased from lower to higher IQ levels. Consequently, this research cannot rule out the possibility that a child's IQ level influences the degree to which the FE is apparent.

The Intelligence of Chinese Children in Hong Kong

In this study the Culture Fair Test was administered to a sample of 9-year-old Clhinese children in Hong Kong. The sample was matched for socioeconomic status (SES) to the Hong Kong population. The mean IQ of the sample was 113. This figure needs adjustment for the time interval between the two test standardizations and for comparison with American white children. The effect of these adjustments is to reduce the mean IQ of the Hong Kong children to 104.5.

Integration of the Literature on the Intelligence of Japanese Children and Analysis of the Data from a Sequential Simultaneous Perspective

This study reviewed, integrated and interpreted the literature on Japanese intelligence that followed from Lynn's (1982) conclusion of an 11-point WISC-R IQ superiority of Japanese over American children and adolescents. Reanalyses of Lynn's data, as well as subsequent research, suggest that the supposed 11-point Japanese superiority is exaggerated. In addition, this study explored the hypothesis that Japanese children perform significantly better on simultaneous processing than on sequential processing. Regression equations derived from a sample of American children who were tested on both the WISC-R and K-ABC were applied to Lynn's data on Japanese children. Results of these analyses supported the hypothesis of a discrepancy, with Japanese Simultaneous processing being significantly greater than Sequential processing, relative to American children, across virtually the entire 6-to 16-year age range.

Secular Increases in Reasoning and Mathematical Abilities in Britain,1972-84

A number of recent studies have shown that the intelligence of children has been increasing over the last half-century. Evidence from the standardizations of the Cognitive Abilities Test in Britain in 1972 and 1984 confirms this. It was found that the increases over a 12-year period were 3.0 IQ points for Non-Verbal Ability, 3.6 points for Verbal and 6.4 points for Quantitative. The inferences drawn are that there has been no diminution in recent years in the rate of increase of intelligence; that the rate of increase of the reasoning primary ability in Britain is approximately 2.5-3.0 IQ points per decade; that the verbal comprehension primary has been increasing at a lower rate; and that crystallized educational abilities show variable rates of increase depending on changes in the curricula taught in schools and the motivation of pupils and teachers.

Normative Scores for Standard Neuropsychological Tests in the Oldest Old From the French Population-Based PAQUID Study

There is an obvious lack of validated norms for elderly persons aged 85 and older for the large majority of the neuropsychological tests used in clinical practice. Yet this range of "oldest-old" individuals drastically increases worldwide and is the more likely to develop dementia. Providing clinicians validated and updated norms to accurately evaluate cognitive functioning in this population is an important issue in geriatrics. This study provides normative scores for 7 neuropsychological tests commonly used in clinical practice. Data were collected in a sample of 283 subjects aged 85 and older, included in the PAQUID study, a population-based cohort conducted in France. Normative scores were calculated according to 2 age ranges and 2 educational levels, and are presented in percentiles. The norms provided in the present study involve 7 tests that are widely used in the neuropsychological assessment of geriatrics populations and should be of help for clinicians.

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 1985-86 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.

An increase of intelligence measured by the WPPSI in China, 1984-2006

Normative data for 5-6 year olds on the Chinese Preschool and Primary Scale of Intelligence (WPPSI) are reported for samples tested in 1984 and 2006. There was a significant increase in Full Scale IQ of 4.53 points over the 22 year period, representing a gain of 2.06 IQ points per decade. There were also significant increases in Verbal IQ of 4.27 points and in Performance IQ of 4.08 points.

The Increase in Colored Progressive Matrices Test Performance in Individuals With Down Syndrome: A Qualitative and Quantitative Review

It is well known that a normal population improves its IQ test scores by about 3 points per decade. This is called the Flynn effect and has been explained in different and sometimes contrasting ways. Few and ambiguous data are available on any Flynn effect in individuals with an atypical development, such as those with intellectual disabilities: some studies report evidence of the Flynn effect, whereas others do not. The main objective of the present study was to analyze the performance of individuals with Down syndrome (DS) compared with a sample of typically developing (TD) children in the Colored Progressive Matrices (CPM) test, which measures abstract reasoning and is commonly used to estimate IQ, to see whether a Flynn effect is present. Our results suggest that the Flynn effect in the DS population depends on the individual’s age.

Exploring the Flynn effect in mentally retarded adults by using a nonverbal intelligence test for children

Increases in the scores on IQ tests across generations have been called the Flynn effect (FE). One of the unresolved questions is whether the FE affects all subsamples of the intellectual ability distribution equally. The present study was aimed at determining the size of the FE in moderately mentally retarded individuals. A nonverbal intelligence test developed for children, the Snijders-Oomen Nonverbal Intelligence Test (SON), was administered to 32 retarded adults with a mental age of 3-6 years. Sixty-nine children with a biological age in the same range and with normal intelligence served as a comparison group. Both an older and a more recent version of the SON were presented to all participants in a counterbalanced order. The proportion of items answered correctly was taken as a measure of the dependent variable. It was found that a FE existed in both the group of children and in the group of retarded adults, but that the FE was largest in the latter group. The importance of not using obsolete test norms when diagnosing mental retardation was stressed, and possible causes of the Flynn effect were discussed.

The Flynn Effect within Subgroups in the U.S.: Gender, Race, Income, Education, and Urbanization Differences in the NLSY-Children Data

Although the Flynn Effect has been studied widely across cultural, geographic, and intellectual domains, and many explanatory theories have been proposed, little past research attention has been paid to subgroup differences. Rodgers and Wänström (2007) identified an aggregate-level Flynn Effect (FE) at each age between 5 and 13 in the Children of the National Longitudinal Survey of Youth (NLSYC) PIAT-Math data. FE patterns were not obtained for Reading Recognition, Reading Comprehension, or Digit Span, consistent with past FE research suggesting a closer relationship to fluid intelligence measures of problem solving and analytic reasoning than to crystallized measures of verbal comprehension and memory. These prior findings suggest that the NLSYC data can be used as a natural laboratory to study more subtle FE patterns within various demographic subgroups. We test for subgroup Flynn Effect differences by gender, race/ethnicity, maternal education, household income, and urbanization. No subgroups differences emerged for three demographic categories. However, children with more educated (especially college educated) mothers and/or children born into higher income households had an accelerated Flynn effect in their PIAT-M scores compared to cohort peers with lower educated mothers or lower income households. We interpret both the positive and the null findings in relation to previous theoretical explanations.

Normative Data for Raven's Coloured Progressive Matrices Scale in Yemen

Results are reported for a standardization sample of 986 6- to 11-yr.-olds for the Coloured Progressive Matrices in Yemen. Younger children performed better than older children relative to British norms, and there was no significant sex difference in means or variability. In relation to a British IQ of 100 ( SD=15), the sample obtained an average IQ of approximately 81.

A study of intelligence in Estonia

The Standard Progressive Matrices was standardised in Estonia in 2001 on a sample of 2,689 12- to 18-yr.-olds. The mean IQ of the Estonian sample was approximately 5 points higher than British IQ norms of 1979. Adjustment for the estimated secular increase of intelligence in Britain reduces the mean IQ of the Estonian sample to 100.2, in relation to a British mean of 100. A particular interest of the result from Estonia is that the intelligence of a European population is apparently not impaired by decades of low living standards.

A study of IQ in Lithuania

Data for the Colored Progressive Matrices were collected for a sample of 259 8- to 12-yr.-old children in Lithuania in 1999. In relation to the British 1979 standardization sample the mean IQ of the Lithuanian children was 92.2. Adjusted for the estimated secular increase of intelligence in Britain, the Lithuanian mean IQ is estimated at 90.