What has caused the Flynn effect? Secular increases in the Development Quotients of infants

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.

Stability of developmental milestones: Insights from a 44-year analysis

Using standardized test procedures is a reliable way of assessing early childhood development in the pediatric setting. However, normal population's developmental parameters may change over time. The aim of this study was to determine whether a change of developmental percentiles is present in infants in Germany during recent decades. Measured by an established German diagnostic instrument (Münchener Funktionelle Entwicklungsdiagnostik) we cross-sectionally compared developmental data (cognition, expressive language, language comprehension, fine and gross motor skills, social development, daily-living skills) of children aged 0-36 months collected in the 1970s and in 2018. N = 2065 children and their parents were included (1970s sample: N = 1660 and 2018 sample: N = 405). The T-Test of dependent variables showed nonsignificant differences in the developmental scales. We hypothesized an infant Flynn effect, but the results of this study suggest that there are no developmental changes associated with the 50th percentile. Nevertheless, it is critical to emphasize the need for periodic revision and re-norming of developmental test procedures, even in the absence of significant changes in individual items.

It Runs in the Family: Testing for Longitudinal Family Flynn Effects

The Flynn effect refers to increases over time in measured (particularly fluid) intelligence of approximately 3 IQ points per decade. We define the Flynn effect at the family level, using longitudinal data and two new family-level cohort definitions. Multilevel growth curve analyses of the National Longitudinal Survey of Youth 1979 data showed that children in families with later-born mothers had higher average PIAT math scores, and lower average reading comprehension scores and growth, in young and middle childhood. Children in families where the first child was born later had higher average PIAT math, reading recognition, and reading comprehension scores, as well as larger developmental growth. The latter family-level Flynn effects were of higher magnitudes than the usual individual-level Flynn effect found in previous studies. Our results, showing family level-intercept and slope Flynn effects for both maternal birthyear and first child birthyear, have implications for research aiming to explain the Flynn effect.

Parental Self-Perception, Parental Investment, and Early Childhood Developmental Outcomes: Evidence From Rural China

Using a three-wave longitudinal survey conducted in 815 households in rural Western China, this study aims to examine the association between parental self-perception and early childhood development and the mediation effect of parental investment on the association between parental self-perception and child development when the sample children are at different ages in the early childhood (18-30, 22-36, and 49-65 months). The results demonstrate that parental self-perception are positively and significantly associated with child social-emotional development in all three ages of childhood (from 18 to 65 months). Positive and significant association between parental self-perception and child cognitive development is found in the ages from 22 to 65 months. In addition, findings of this study show that parental investment plays a mediating role in the association between parental self-perception and child cognitive development. The study calls on policymakers to help to strengthen parental self-perception and parental investment related to early childhood development, which should result in better child development in rural China.

A Half Century of Progress in US Student Achievement: Agency and Flynn Effects, Ethnic and SES Differences

Policymakers, conceptualized here as principals, disagree as to whether US student performance has changed over the past half century. To inform conversations, agents administered seven million psychometrically linked tests in math (m) and reading (rd) in 160 survey waves to national probability samples of cohorts born between 1954 and 2007. Estimated change in standard deviations (sd) per decade varies by agent (m: –0.10sd to 0.27sd, rd: –0.02sd to 0.12sd). Consistent with Flynn effects, median trends show larger gains in m (0.19sd) than in rd (0.04sd), though rates of progress for cohorts born since 1990 have increased in rd but slowed in m. Greater progress is shown by students tested at younger ages (m: 0.31sd, rd: 0.08sd) than when tested in middle years of schooling (m: 0.17sd, rd: 0.03sd) or toward the end of schooling (m: 0.06sd, rd: 0.02sd). Young white students progress more slowly (m: 0.28sd, rd: 0.09sd) than Asian (m: 46sd, rd: 0.28sd), black (m: 0.36sd, rd: 0.19sd), and Hispanic (m: 0.29sd, rd: 0.13sd) students. These ethnic differences generally attenuate as students age. Young students in the bottom quartile of the SES distribution show greater progress than those in the top quartile (difference in m: 0.08sd, in rd: 0.15sd), but the reverse is true for older students. Moderators likely include not only changes in families and schools but also improvements in nutrition, health care, and protection from contagious diseases and environmental risks. International data suggest that subject and age differentials may be due to moderators more general than just the United States.

Sleep problems and infant motor and cognitive development across the first two years of life: The Beijing Longitudinal Study

The present study examined bidirectional effects between sleep problems (nocturnal awakenings and insufficient nocturnal sleep) and infant development (gross motor, fine motor, and cognition) in a sample of 182 infants (89 girls) and their parents living in Beijing (China). Using 3 waves of longitudinal data (at 6 months, 1 year, and 2 years of age), this study (a) explored the differences in sleep patterns and developmental outcomes between infants in the current sample and infants from other cultures; and primarily examined (b) whether nocturnal awakenings and insufficient nocturnal sleep prospectively predicted infant development; (c) or whether infant development predicted sleep problems. Mothers reported their children's sleep problems, and infant development was assessed with Bayley III. Sleep patterns of Beijing infants were slightly different from those from Finland and Singapore, and most scores on Bayley III in this Beijing sample were higher than those in Danish, Dutch and Sri Lankan samples. Sleep problems and developmental measures were stable across the 3 times of assessments, but cross-lagged associations were limited in number and strength. High scores on the Bayley at 6 months predicted less nocturnal awakenings at 1 year of age. Insufficient nocturnal sleep at 1 year predicted poor fine motor development at 2 years. Thus, findings suggest some bidirectional associations between infant development and sleep problems and further highlight the need to understand these relations within specific cultural contexts.

Genetically informed, multilevel analysis of the Flynn Effect across four decades and three WISC versions

This study investigated the systematic rise in cognitive ability scores over generations, known as the Flynn Effect, across middle childhood and early adolescence (7-15 years; 291 monozygotic pairs, 298 dizygotic pairs; 89% White). Leveraging the unique structure of the Louisville Twin Study (longitudinal data collected continuously from 1957 to 1999 using the Wechsler Intelligence Scale for Children [WISC], WISC-R, and WISC-III ed.), multilevel analyses revealed between-subjects Flynn Effects-as both decrease in mean scores upon test re-standardization and increase in mean scores across cohorts-as well as within-child Flynn Effects on cognitive growth across age. Overall gains equaled approximately three IQ points per decade. Novel genetically informed analyses suggested that individual sensitivity to the Flynn Effect was moderated by an interplay of genetic and environmental factors.

The secular trend of intelligence test scores: The Danish experience for young men born between 1940 and 2000

The present study investigated the Danish secular trend of intelligence test scores among young men born between 1940 and 2000, as well as the possible associations of birth cohort changes in family size, nutrition, education, and intelligence test score variability with the increasing secular trend. The study population included all men born from 1940 to 2000 who appeared before a draft board before 2020 (N = 1,556,770). At the mandatory draft board examination, the approximately 19-year-old men underwent a medical examination and an intelligence test. In the statistical analyses, the IQ mean and standard deviation (SD) were estimated separately for each of the included annual birth cohorts based on information from birth cohorts with available total intelligence test scores for all tested individuals (i.e. 1940-1958 and 1987-2000; the mean and SD were interpolated for the intermediate birth cohorts). Moreover, the possible associations with birth cohort changes in family size, height as a proxy for nutritional status, education, and IQ variability were investigated among those birth cohorts for whom a secular increase in intelligence test scores was found. The results showed that the estimated mean IQ score increased from a baseline set to 100 (SD: 15) among individuals born in 1940 to 108.9 (SD: 12.2) among individuals born in 1980, since when it has decreased. Focusing on the birth cohorts of 1940-1980, for whom a secular increase in intelligence test scores was found, birth cohort changes in family size, height, and education explained large proportions of the birth cohort variance in mean intelligence test scores, suggesting that these factors may be important contributors to the observed Flynn effect in Denmark.

Home Improvement: Evaluating Secular Changes in NLSY HOME-Cognitive Stimulation and Emotional Support Scores

This study evaluated changes over time in the quality of children's home environment, using the Home Observation Measurement of the Environment (HOME). Longitudinal increases in HOME scores were predicted by both theory and past empirical results. Analysis of the National Longitudinal Survey of Youth Children data (N = 5715, aged 0-14) suggested that HOME scores have been increasing, and that the increase is a family-level phenomenon. The data were a sample of children born to mothers who were approximately representative of the United States in 1979. An increase in HOME scores occurred primarily for the three age categories younger than ten. Effect sizes were of approximately the same magnitude as the Flynn effect for intelligence. These results have implications for policy and future research regarding the home environment.

Breastfeeding Insufficiencies: Common and Preventable Harm to Neonates

Insufficient milk intake in breastfed neonates is common, frequently missed, and causes preventable hospitalizations for jaundice/hyperbilirubinemia, hypernatremia/dehydration, and hypoglycemia - accounting for most U.S. neonatal readmissions. These and other consequences of neonatal starvation and deprivation may substantially contribute to fully preventable morbidity and mortality in previously healthy neonates worldwide. Previous advanced civilizations recognized this problem of breastfeeding insufficiencies and had an infrastructure to solve it: Wetnursing, shared nursing, and prelacteal feeding traditions used to be well-organized and widespread. Modern societies accidentally destroyed that infrastructure. Then, modern reformers missing a few generations of direct knowledge transmission about safe breastfeeding invented a new, historically anomalous conception of breastfeeding defined in terms of exclusivity. As that new intervention has become increasingly widespread, so too have researchers widely reported associated possible harms of the longer neonatal starvation/deprivation and later infant under-nutrition periods that it creates when breastfeeding is insufficient. Early insufficient nutrition/hydration has possible long-term effects including neurodevelopmental consequences such as attention deficit hyperactivity disorder, autism, cerebral palsy, cognitive and developmental delay, epilepsy, hearing impairment, kernicterus, language disorder, mood disorders, lower IQ, and specific learning disorder. Current early infant feeding guidelines conflict with the available evidence. Recent reform efforts have tended to focus on using more technology and measurement to harm fewer neonates instead of proposing the indicated paradigm shift in early infant feeding to prevent more harm. The scientific evidence is already sufficient to mandate application of the precautionary principle to feed neonates early, adequate, and often milk before mothers' milk comes in and whenever signs of hunger persist, mitigating possible risks including death or disability. In most contexts, the formula is the best supplementary milk for infants at risk from breastfeeding insufficiencies. National-level reviews of scientific evidence, health policy, and research methods and ethics are needed to initiate the early infant feeding paradigm shift that the data already support. Policy experiments and related legislative initiatives might also contribute to the shift, as insurers might decline or be required by law to decline reimbursing hospitals for costs of this type of preventable hospitalization, which otherwise generates profit.

Sagittal Synostosis and Its Association With Cognitive, Behavioral, and Psychological Functioning: A Meta-analysis

IMPORTANCE

Findings on the cognitive, behavioral, and psychological functioning of individuals with sagittal synostosis (SS) are highly disparate, limiting their clinical utility.

OBJECTIVE

To identify and review research on individuals with SS and to determine whether, and to what extent, they experience cognitive, behavioral, and psychological difficulties compared with their healthy peers or normative data for each measure.

DATA SOURCES

PubMed, Scopus, Embase, and PsycINFO were searched through January 2021 with no date restrictions. Scopus citation searches and manual checks of the reference lists of included studies were conducted.

STUDY SELECTION

Studies included participants of any age who had received a diagnosis of single-suture (isolated or nonsyndromic) SS or scaphocephaly and who had been assessed on cognitive, behavioral, and psychological outcomes.

DATA EXTRACTION AND SYNTHESIS

Data were independently extracted by 2 reviewers. Case-control outcomes (individuals with SS vs healthy peers or normative data) were compared using random-effects models with 3 effect sizes calculated: weighted Hedges g (gw), odds ratios (ORs), and mean prevalence rates. This study follows the Meta-analysis of Observational Studies in Epidemiology (MOOSE) reporting guidelines.

MAIN OUTCOMES AND MEASURES

Findings were categorized by surgical status (conservatively managed, presurgery, postsurgery, or combined); domain (eg, general cognition); type of cognitive, behavioral, or psychological measure (objective or subjective); and source of comparison data (peers or normative data).

RESULTS

Data from 32 studies, involving a pooled sample of 1422 children and adults with SS (mean [SD] age at assessment, 5.7 [6.6] years; median [interquartile range] age, 3.3 [0.5-10.3] years), were analyzed. Data on sex were available for 824 participants, and 642 (78%) were male. Individual study results varied substantially. Objective tests identified significant moderate group differences on 3 of 16 examined domains: presurgical motor functioning (3 studies; gw = -0.42; 95% CI, -0.67 to -0.18; P < .001), postsurgical short-term memory (2 studies; gw = -0.45; 95% CI, -0.72 to -0.17; P < .001), and postsurgical visuospatial ability (6 studies; gw = 0.31; 95% CI, 0.18 to 0.44; P < .001). Prevalence estimates and ORs varied widely, with 15 studies showing prevalence estimates ranging from 3% to 37%, and 3 studies showing ORs ranging from 0.31 (95% CI, 0.01 to 6.12) for processing speed in the conservatively managed sample to 4.55 (95% CI, 0.21 to 98.63) for postsurgical visuospatial abilities.

CONCLUSIONS AND RELEVANCE

In this meta-analysis, findings for the functioning of participants with SS were highly disparate and often of low quality, with small samples sizes and control groups rarely recruited. Nonetheless, the findings suggest that some individuals with SS experience negative outcomes, necessitating routine assessment.

Trajectories of child cognitive development during ages 0-3 in rural Western China: prevalence, risk factors and links to preschool-age cognition

BACKGROUND

Cognitive development after age three tends to be stable and can therefore predict cognitive skills in later childhood. However, there is evidence that cognitive development is less stable before age three. In rural China, research has found large shares of children under age three are developmentally delayed, yet little is known about the trajectories of cognitive development between 0 and 3 years of age or how developmental trajectories predict later cognitive skills. This study seeks to describe the trajectories of child cognitive development between the ages of 0-3 years and examine how different trajectories predict cognitive development at preschool age.

METHODS

We collected three waves of longitudinal panel data from 1245 children in rural Western China. Child cognitive development was measured by the Bayley Scales of Infant Development when the child was 6-12 months and 22-30 months, and by the Wechsler Preschool and Primary Scale of Intelligence-Fourth Edition when the child was 49-65 months. We used the two measures of cognitive development before age three to determine the trajectories of child cognitive development.

RESULTS

Of the children, 39% were never cognitively delayed; 13% were persistently delayed; 7% experienced improving cognitive development; and 41% experienced deteriorating development before age 3. Compared to children who had never experienced cognitive delay, children with persistent cognitive delay and those with deteriorating development before age 3 had significantly lower cognitive scores at preschool age. Children with improving development before age 3 showed similar levels of cognition at preschool age as children who had never experienced cognitive delay.

CONCLUSIONS

Large shares of children under age 3 in rural Western China show deteriorating cognitive development from infancy to toddlerhood, which predict lower levels of cognition at preschool age. Policymakers should invest in improving cognitive development before age 3 to prevent long-term poor cognition among China's rural children.

College students in the western world are becoming less emotionally intelligent: A cross-temporal meta-analysis of trait emotional intelligence

OBJECTIVE

Over the last two decades, Western society has undergone a marked cultural transformation characterized by rising individualism. Concurrently, the digital landscape has transformed through the rise of social media and smartphones. These factors have previously been implicated in changing individuals' attitudes, behavior, and interpersonal interactions. We investigated whether these societal changes have coincided with changes in trait emotional intelligence (EI) over the last 17 years in Western university students.

METHOD

We examined this question using a cross-temporal meta-analysis (k = 70; N = 16,917).

RESULTS

There was no change in overall trait EI; however, the trait EI domains "well-being," "self-control," and "emotionality" demonstrated significant decreases with time, after controlling for gender composition and between-country differences.

CONCLUSION

We discuss these findings in relation to how they contribute to our understanding of trait EI, and how they add to the literature on how Western society is changing with time.

Parallelization: the Fourth Leg of Cultural Globalization Theory

Extending Pieterse's (1996) tripartite cultural globalization theory consisting of homogenization, hybridization and polarization, the current article outlines a set of exemplifications and justifications of a fourth theoretical underpinning labeled parallelization. The theory implies that at a global scale, crucial events that appear paradoxical or contradictory occur at the same time, such as carbon emissions due to growth-fixated global capitalism, while the causes of carbon emissions lead to greater resilience against the consequences of carbon emissions as wealth accumulates. Other examples discussed are large-scale migration flows which lead to increased segregation in host societies while integration of migrants occur as a parallel process; secularization visa-à-vis the resurgence of religions; clear indications of that the biological component of cognitive abilities decreases due to fertility patterns in many locations around the globe, while the IQ test scores have risen as a consequence of various environmental factors.

The Relational Abilities Index+: Initial Validation of a Functionally Understood Proxy Measure for Intelligence

The Relational Abilities Index (RAI) has shown considerable utility as a functional proxy measurement of intellectual performance by providing a metric of an important skill set known as relational skills, which are proposed to underlie much of what we conceive of as intellectual behavior. The Relational Abilities Index+ (RAI+) assesses performance across an extended range of relational skills (Same/Opposite, More/Less, Same/Different, Before/After, and Analogy), and has been designed to provide a more comprehensive and nuanced assessment of relational skills. The current study aims to investigate the validity and utility of the RAI+ by assessing its degree of correlation with well-established assessments of intelligence (WASI), numeracy (WAIS: Arithmetic), and educational attainment (WIAT-T-II). Results indicate that the RAI+ displays considerable efficacy in predicting intellectual performance and numeracy, but not educational attainment.

The Flynn effect for fluid IQ may not generalize to all ages or ability levels: a population-based study of 10,000 US adolescents

Generational changes in IQ (the Flynn Effect) have been extensively researched and debated. Within the US, gains of 3 points per decade have been accepted as consistent across age and ability level, suggesting that tests with outdated norms yield spuriously high IQs. However, findings are generally based on small samples, have not been validated across ability levels, and conflict with reverse effects recently identified in Scandinavia and other countries. Using a well-validated measure of fluid intelligence, we investigated the Flynn Effect by comparing scores normed in 1989 and 2003, among a representative sample of American adolescents ages 13-18 (n=10,073). Additionally, we examined Flynn Effect variation by age, sex, ability level, parental age, and SES. Adjusted mean IQ differences per decade were calculated using generalized linear models. Overall the Flynn Effect was not significant; however, effects varied substantially by age and ability level. IQs increased 2.3 points at age 13 (95% CI=2.0, 2.7), but decreased 1.6 points at age 18 (95% CI=-2.1, -1.2). IQs decreased 4.9 points for those with IQ<70 (95% CI=-4.9, -4.8), but increased 3.5 points among those with IQ>130 (95% CI=3.4, 3.6). The Flynn Effect was not meaningfully related to other background variables. Using the largest sample of US adolescent IQs to date, we demonstrate significant heterogeneity in fluid IQ changes over time. Reverse Flynn Effects at age 18 are consistent with previous data, and those with lower ability levels are exhibiting worsening IQ over time. Findings by age and ability level challenge generalizing IQ trends throughout the general population.

Trends and determinants of the Flynn effect in cognitive functioning among older individuals in 10 European countries

BACKGROUND

Although cognitive performance levels in old age have increased in most countries, recent evidence documents a slowing down or even decline in cohort gains in highly developed countries. The aim of this study was to assess trends and determinants in secular cohort gains in cognitive functioning among older individuals and whether cohort gains are levelling off in most advanced countries.

METHODS

Data for individuals aged between 50 and 84 years from the Survey of Health, Ageing and Retirement in Europe in 10 European countries between 2004 and 2013 (n=92 739) were used to assess country and age-specific changes in immediate word recall. Multivariate random intercept models were used to assess associations between secular cohort changes in immediate word recall, initial performance levels and changes in country-level socio-demographic characteristics.

RESULTS

Performance in immediate word recall improved in all countries between 2004 and 2013 (from 4.40 to 5.08 words, P<0.05). However, secular cohort gains were significantly smaller in countries with initially higher performance levels (coeff.=-0.554, 95% CI -0.682 to -0.426). Changes in socio-demographic and health conditions, including decreases in cardiovascular disease, physical activity and educational achievement, were associated with larger secular cohort gains.

CONCLUSIONS

Results may either reflect that some countries are approaching the limits of cognitive plasticity, are slowing in their progress or that societal structures have not yet been optimised to improve cognitive abilities in midlife and beyond, or a combination of these interpretations.

Prenatal Internal Locus of Control Is Positively Associated with Offspring IQ, Mediated through Parenting Behavior, Prenatal Lifestyle and Social Circumstances

Locus of control (LOC) is a measure that identifies the likelihood as to whether an individual considers what happens to him is largely a matter of luck or fate (known as externally oriented) or whether it is something that the individual can influence (internality). Here we have used data collected as part of the Avon Longitudinal Study of Parents and Children (ALSPAC) to determine the associations between the mothers’ LOC orientation before the birth of the child and her child’s cognition measured at age 8. Using results from 6801 children we show that maternal internal LOC is associated with increased ability in offspring IQ, as measured using the WISC, with children of internally oriented mothers having an advantage of approximately 7 IQ points at age 8. As a sensitivity analysis we used the IQ test results of a sample of 986 preschool children tested using the WPSSI at age 4. A similar advantage was found among the offspring of the internally oriented mothers. We investigated mechanistic explanations for these results firstly by determining the extent to which three separate sets of factors known to be influenced by the LOC orientation might explain these findings. We showed that (a) perinatal life-style exposures, (b) parenting attitudes and strategies and (c) socio-economic circumstances, largely explain the mechanism through which the internality of the mother influences the cognition of the child. Similar effects were found using the smaller sample tested at age 4. The results indicate that efforts made to foster internality in adolescents and young adults prior to parenthood may result in improvements in the cognitive development of the next generation. Intervention studies are urgently needed.

Double Decomposition of Level-1 Variables in Multilevel Models: An Analysis of the Flynn Effect in the NSLY Data

This paper introduces an extension of cluster mean centering (also called group mean centering) for multilevel models, which we call "double decomposition (DD)." This centering method separates between-level variance, as in cluster mean centering, but also decomposes within-level variance of the same variable. This process retains the benefits of cluster mean centering but allows for context variables derived from lower level variables, other than the cluster mean, to be incorporated into the model. A brief simulation study is presented, demonstrating the potential advantage (or even necessity) for DD in certain circumstances. Several applications to multilevel analysis are discussed. Finally, an empirical demonstration examining the Flynn effect (Flynn, 1987 ), our motivating example, is presented. The use of DD in the analysis provides a novel method to narrow the field of plausible causal hypotheses regarding the Flynn effect, in line with suggestions by a number of researchers (Mingroni, 2014 ; Rodgers, 2015 ).

Systematic Review and Meta-Analysis: Fussing and Crying Durations and Prevalence of Colic in Infants

OBJECTIVE

To determine the mean duration of fussing and crying and prevalence of colic using modified Wessel criteria in infants in the first 3 months of life.

STUDY DESIGN

A systematic literature search was performed using the databases Medline, PsycINFO, and Embase. The major outcome measure was mean total fuss/cry duration during 24 hours at ages 1-2 weeks (11 samples), 3-4 weeks (6 samples), 5-6 weeks (28 samples), 8-9 weeks (9 samples), and 10-12 weeks (12 samples).

RESULTS

Of 5687 articles reviewed, 28 diary studies (33 samples) were suitable for inclusion in meta-analysis; these studies included 8690 infants. No statistical evidence for a universal crying peak at 6 weeks of age across studies was found. Rather, the mean fuss/cry duration across studies was stable at 117-133 minutes (SDs: 66-70) in the first 6 weeks and dropped to a mean of 68 minutes (SD: 46.2) by 10-12 weeks of age. Colic was much more frequent in the first 6 weeks (17%-25%) compared with 11% by 8-9 weeks of age and 0.6% by 10-12 weeks of age, according to modified Wessel criteria and lowest in Denmark and Japan.

CONCLUSIONS

The duration of fussing/crying drops significantly after 8-9 weeks of age, with colic as defined by modified Wessel criteria being rare in infants older than 9 weeks. Colic or excessive fuss/cry may be more accurately identified by defining fuss/cry above the 90th percentile in the chart provided based on the review.

Assessing the intellectual ability of asylum seekers

The European Union has seen an increased number of asylum seekers and economic migrants over the past few years. There will be request to assess some of these individuals to see if they have an intellectual disability (ID). If this is to be done using the current internationally recognized definitions of ID, we will need to be confident that the IQ tests we have available are able to accurately measure the IQs of people from developing countries. The literature showing substantial differences in the mean measured IQs of different countries is considered. It is found that, although there are numerous problems with these studies, the overall conclusion that there are substantial differences in mean measured IQ is sound. However, what is not clear is whether there are large differences in true intellectual ability between different countries, how predictive IQ scores are of an individual from a developing country ability to cope, and whether or not an individual's IQ would increase if they go from a developing country to a developed one. Because of these uncertainties, it is suggested that a diagnosis of ID should not be dependent on an IQ cut-off point when assessing people from developing countries.

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.

Effect of prenatal and postnatal malnutrition on intellectual functioning in early school-aged children in rural western China

The aim of this study was to evaluate the effect of prenatal and postnatal malnutrition on the intellectual functioning of early school-aged children. We followed the offspring of women who had participated in a trial of prenatal supplementation with different combinations of micronutrients and who remained resident in the study field. We measured their intellectual functioning using the Wechsler intelligence scale for children (WISC-IV). Height-for-age, weight-for-age, and body mass index (BMI)-for-age were used as anthropometric nutritional status indices. Four of the 5 composite scores derived from the WISC-IV, except for working memory index (WMI), were significantly lower in low birth weight children after adjusting for confounds. All 5 composite scores, including full-scale intelligence quotient (FSIQ), verbal comprehension index (VCI), WMI, perceptual reasoning index (PRI), and processing speed index (PSI) were significant lower in stunted and underweight children. The differences in the means of WISC-IV test scores were greatest between stunted and nonstunted children. The means for FSIQ, VCI, WMI, PRI, and PSI were as follows: 5.88 (95% confidence interval [CI]: 2.84-8.92), 5.08 (95% CI: 1.12-8.41), 4.71 (95% CI: 1.78-7.66), 6.13 (95% CI: 2.83-9.44), and 5.81 (95% CI: 2.61-9.00). These means were lower in stunted children after adjusting for confounds. Our results suggest the important influences of low birth weight and postnatal malnutrition (stunting, low body weight) on intellectual functioning in early school-aged children.

How Much Does WAIS-IV Perceptual Reasoning Decline Across the 20 to 90-Year Lifespan When Processing Speed is Controlled?

The most prominent pattern of cognitive change over the lifespan centers on the difference between patterns of maintained abilities on tests of crystallized knowledge and patterns of steady decline on tests of problem solving and processing speed. Whereas the maintained-vulnerable dichotomy is well established in the literature, questions remain about cognitive decline in problem solving when processing speed is controlled. This relationship has been examined in cross-sectional studies that typically used non-clinical tests with non-representative samples of adults. This study extended these findings to the most popular clinical test, the Wechsler Adult Intelligence Scale -4th ed. (WAIS-IV), using its carefully stratified sample as the source of data (ages 20-90 for Indexes, ages 16-90 for Perceptual Reasoning subtests). Multivariate Analysis of Covariance (MANCOVA) revealed that 70-80% of the variance in declining reasoning ability was shared with the speed factor. This was true (a) on the index and subtest level and (b) regardless of the type of problem-solving task employed. Such robust findings have important clinical and research implications for neuropsychologists, who most frequently use the Wechsler scales as part of their assessment battery.

Why did children grow so well at hard times? The ultimate importance of pathogen control during puberty

Background and objectives: Secular increase in human height and performance occurred in Europe throughout the 20th century despite the temporally worsening access to nutrients during and after World War II. This pattern is paradoxical under the assumption of the major impact of pre- and postnatal growth conditions for determination of adult size and human capital.

Methodology: We examined the anthropometric parameters of Estonian girls born between 1938 and 1953, and measured around the age of 17 (n = 1475). This period involved two opposite trends in the economic and epidemiological situation: increasing birth-time economic hardships during the war and particularly in the post-war period, and decreasing infant mortality (a proxy of disease burden) after 1947.

Results: Height of girls was negatively affected by the number of siblings and positively by parental socioeconomic position, but these effects were weaker than the secular trend. Leg length (an indicator of pre-pubertal growth conditions) was independent of age and birth date while all other traits, including measures of performance (cranial volume, lung capacity and handgrip strength) showed acceleration. The best predictor of size at age 17 was, in most cases, infant mortality in the year when the girls were aged 11.

Conclusions and implications: Reduction of disease burden during pubertal growth can override effects of resource shortage at birth. Our results also support the idea that increasing efficiency of pathogen control can contribute to the secular increase in cognitive abilities, i.e. the Flynn effect, and that epidemiological transition is the main driver of secular increase in human capital.

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.

Assessing the Flynn Effect in the Wechsler Scales

The current study examined the Flynn Effect (i.e., the increase in IQ scores over time) across all editions of the Wechsler Adult Intelligence Scale (WAIS), Wechsler Intelligence Scale for Children (WISC), and Wechsler Preschool and Primary Scale of Intelligence (WPPSI). By reverse engineering the correlation and scale score transformations from each Wechsler edition’s technical manual, we made a mean and covariance matrix using the subtests and age groups that were in common for all editions of a given instrument. The results indicated that when aggregated, there was a FE of 0.44 IQ points/year. This Wechsler instrument used, however, moderates the FE, with the WISC showing the largest FE (0.73 IQ points/year) and the WAIS showing a smallest FE (0.30 IQ points/year). Moreover, this study found that the amount of invariant indicators across instruments and age groups varied substantially, ranging from 51.53% in the WISC for the 7-year-old group to 10.00% in the WPPSI for the 5- and 5.5-year-old age groups. Last, we discuss future direction for FE research based on these results.

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.