Flynn Effect Research Articles

B - 107 Is the Flynn Effect Present in a Veteran Outpatient Clinic Sample?

Abstract Objective The Flynn Effect refers to improvement in cognitive scores over time due to advancements in education quality, nutrition, and socioenvironmental variables. Recent studies suggest cognitive scores may plateau or decline over time. Characterization of cohort effects in cognitive performance has implications for normative group selection and identification of brain illness. This study examines cognitive performances of veterans using older and newer versions of normative data to determine if a Flynn effect is present. Method Veterans (N = 189) who passed TOMM and completed the Trail-Making Test (TMT), Animal Naming, and California Verbal Learning Test-II (CVLT-II) were selected for inclusion. The sample was 81% male, racially diverse (49% White/Caucasian, 31% Black/African American, 16% Hispanic/Latino, 4% other), and diagnostically diverse (13% no diagnosis, 33% cognitive disorder, 54% psychiatric diagnosis). Normative scores were calculated from CVLT-II/CVLT-3 manuals for Trial 1, Trial 5, and LDFR; ADC Uniform Data Sets (UDS) were used for TMT-A/B and Animals. Wilcoxon matched-pairs signed rank tests examined differences in z-scores across older and newer normative data. Results Median z-scores were significantly lower using updated UDS norms for TMT-A (z = −11.60, p < 0.001), TMT-B (z = −10.41, p < 0.001), and Animals (z = −11.76, p < 0.001), while CVLT Trial 1 z-scores were significantly higher using CVLT-3 norms (z = 11.24, p < 0.001). CVLT Trial 5 and LDFR medians did not differ. Conclusion Findings demonstrate the need to examine cohort differences in normative reference groups to ensure accurate detection of brain illness. Furthermore, the Flynn Effect may not apply uniformly across domains within a period.

The Flynn effect and cognitive decline among americans aged 65 years and older.

To contribute to our understanding of cohort differences and the Flynn effect in the cognitive decline among older Americans, this study aims to compare rates of cognitive decline between two birth cohorts within a study of older Americans and to examine the importance of medical and demographic confounders. Analyses used data from the National Health and Aging Trends Study (2011-2019), which recruited older Americans in 2011 and again in 2015 who were then followed for 5 years. We employed mixed-effect models to examine the linear and quadratic main and interaction effects of year of birth while adjusting for covariates such as annual round, sex/gender, education, race/ethnicity, heart disease, hypertension, diabetes, test unfamiliarity, and survey design. We analyzed data from 11,167 participants: 7,325 from 2011 to 2015 and 3,842 from 2015 to 2019. The cohort recruited in 2015 was born, on average, 5.33 years later than that recruited in 2011 and had higher functioning than the one recruited in 2011 across all observed cognitive domains that persisted after adjusting for covariates. In multivariable-adjusted analyses, a 1-year increase in year of birth was associated with increased episodic memory (β = 0.045, SE = 0.001, p < .001), orientation (β = 0.034, SE = 0.001, p < .001), and executive function (β = 0.036, SE = 0.001, p < .001). Participants born 1 year later had slower rates of decline in episodic memory (β = 0.004, SE = 0.000, p < .001), orientation (β = 0.003, SE = 0.000, p < .001), and executive function (β = 0.001, SE = 0.000, p = .002). Additionally, sex/gender modified this relationship for episodic memory (-0.007, SE = 0.002, p < .001), orientation (-0.005, SE = 0.002, p = .008), and executive function (-0.008, SE = 0.002, p < .001). These results demonstrate the persistence of the Flynn effect in old age across cognitive domains and identified a deceleration in the rate of cognitive decline across cognitive domains. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Requiem for Heterosis as a Cause of the Flynn Effect: Positive Combined Effects of Numbers and Lengths of Homozygosity Runs on Offspring-Parent Differences in Educational Attainment

Requiem for Heterosis as a Cause of the Flynn Effect: Positive Combined Effects of Numbers and Lengths of Homozygosity Runs on Offspring-Parent Differences in Educational Attainment

Measurement-Invariant Fluid Anti-Flynn Effects in Population-Representative German Student Samples (2012-2022).

Generational IQ test scores in the general population were observed to increase over time (i.e., the Flynn effect) across most of the 1900s. However, according to more recent reports, Flynn effect patterns have seemingly become less consistent. So far, most available evidence on this phenomenon has been categorized by drawing on the classic fluid vs. crystallized intelligence taxonomy. However, recent evidence suggests that subdomain-specific trajectories of IQ change may well be more complex. Here, we present evidence for cross-temporal changes in measurement-invariant figural reasoning tasks in three large-scale, population-representative samples of German secondary school students (total N = 19,474). Analyses revealed a consistent pattern of significant and meaningful declines in performance from 2012 to 2022. Results indicate a decrease in figural reasoning of 4.68 to 5.17 IQ points per decade (corresponding to small-to-medium effects, Cohen ds from 0.34 to 0.38). These findings may be interpreted as tentative evidence for a decreasing strength of the positive manifold of intelligence as a potential cause of the increasing number of recent reports about inconsistent IQ change trajectories.

Supplemental Material for The Flynn Effect and Cognitive Decline Among Americans Aged 65 Years and Older

Supplemental Material for The Flynn Effect and Cognitive Decline Among Americans Aged 65 Years and Older

Parental and family determinants of the Flynn effect.

Research about the Flynn effect, the secular rise in IQ, is heavily based on conscript data from successive male birth cohorts. This inevitably means that two distinct phenomena are mixed: fertility differences by IQ group ('compositional Flynn effect'), and any difference between parents and children ('within-family Flynn effect'). Both will influence trends in cognitive ability. We focused on the latter phenomenon, exploring changes in cognitive abilities during adolescence within one generation, and between two successive generations within the same family. We identified determinants and outcomes in three linked generations in the Stockholm Multigenerational Study. School and conscript data covered logical/numerical and verbal scores for mothers at age 13, fathers at 13 and 18, and their sons at 18. Raw scores, and change in raw scores, were used as outcomes in linear regressions. Both parents' abilities at 13 were equally important for sons' abilities at 18. Boys from disadvantaged backgrounds caught up with other boys during adolescence. Comparing fathers with sons, there appeared to be a positive Flynn effect in logical/numeric and verbal abilities. This was larger if the father had a working-class background or many siblings. A Flynn effect was only visible in families where the father had low general cognitive ability at 18. We conclude that there is a general improvement in logical/numeric and verbal skills from one generation to the next, primarily based on improvement in disadvantaged families. The Flynn effect in Sweden during the later 20th century appears to represent a narrowing between social categories.

Eleven articles and 27 authors pay tribute to James Flynn: A summary and critique of special issue articles on the Flynn effect

This article, written by the guest editor, is an introduction to a special issue of Intelligence. The special issue includes eleven research papers on the Flynn effect, each written to pay tribute to the past work by James Flynn, who passed away in December 2020. The papers are organized in the current article into four categories: empirical papers, theoretical papers, methodological papers, and integrative papers. Each paper is summarized separately, and then the papers are discussed in an integrative critique that makes a number of points about the current status of research on the Flynn effect.

Reliability of the g factor over time in Italian INVALSI data (2010-2022): What can achievement-g tell us about the Flynn effect?

Generational intelligence test score gains over large parts of the 20th century have been observed to be negatively associated with psychometric g. Recent reports about changes in the cross-temporal IQ trajectory suggest that ability differentiation may be responsible for both changes in g as well as increasingly (sub-)domain-specific and inconsistent trajectories. Schooling is considered to be a main candidate cause for the Flynn effect, which suggests that school achievement might be expected to show similar cross-temporal developments. In the present study, we investigated evidence for cross-temporal changes in achievement-based g in a formal large-scale student assessment in Italy (i.e., the INVALSI assessment; N = 1,900,000+). Based on data of four school grades (i.e., grades 2, 5, 8, and 10) over 13 years (2010–2022), we observed little evidence for changes in achievement g in general. However, cross-temporal trajectories were differentiated according to school grade, indicating cross-temporal g decreases for lower grade students whilst changes for higher grade students were positive. These findings may be interpreted as tentative evidence for age-dependent achievement-g differentiation. The presently observed achievement g trajectory appears to be consistent with recently observed evidence for a potential stagnation or reversal of cognitive test score gains.

Intercohort upsurge of cognitive ability among the general population in China: Evaluating a Flynn effect

Drawing on data from three waves of the China Family Panel Studies (CFPS), we find a substantial intercohort upsurge of both vocabulary and mathematical abilities among the Chinese general population born between 1935 and 1984. Consistent with the well-established Flynn effect, Chinese adults boost their average vocabulary score by 3.21 points and mathematical score by 3.83 points per decade. Further examinations suggest that the observed intercohort gains in cognition are largely associated with educational expansion, nutritional improvement and reduced family size. These factors together account for about 76% of vocabulary gains and 79% of mathematical gains. Moreover, subgroup analyses reveal that females gain at a much faster pace than do males in terms of both vocabulary and mathematical scores among the studied cohorts, with young females catching up and even surpassing males in the recent cohorts; while rural residents still fall behind their urban counterparts for both vocabulary and mathematical abilities. Taken together, these findings are consistent with the life history theory and strongly support the fundamental role of socioenvironmental changes in producing the Flynn effect.

A synthetic theory to integrate and explain the causes of the Flynn effect: The Parental Executive Model

The Flynn effect is one of the most interesting puzzles in psychology. Measured intelligence increased worldwide for a century, primarily in the fluid domain. Some increases may be flattening and/or reversing. Around 20 theories have been developed to explain the Flynn effect; most have empirical or conceptual weaknesses, though they also have strengths and face validity. The role of parents has been given only slight attention in past theorizing. We propose a new synthetic theory, the Parental Executive Model (the PEM) that integrates, organizes, and takes advantage of most previous theories. To structure our paper, we begin with a description of synthetic theories, and how to evaluate them (which has unique and difficult challenges). Following, we review the Flynn effect, and briefly summarize the new theory. Next, recent research is reviewed suggesting the value of re-conceptualizing the location of the Flynn effect to focus on families, and parents. Following, we describe the PEM, which states that parents – and teachers, authors, friends, etc. – use their agency to manage children's intellectual growth. The PEM posits that many (not all) parents subjectively optimize their children's intellectual outcomes, taking advantage of some subset of available resources – nutrition, education, technology, health care, etc. Cross-generational momentum occurs as parenting improves across generations. Prior research motivating the PEM is reviewed, and methods to evaluate the PEM are discussed. Finally, one recent empirical evaluation of the PEM is reviewed, that the cognitive home environment has been improving over time.

Seventy years, 1000 samples, and 300,000 SPM scores: A new meta-analysis of Flynn effect patterns

Several studies have investigated and found the gradual rise in IQ over time or the Flynn effect (FE) but inconsistent results on the FEs across types of countries and age groups were reported. The current cross-temporal meta-analysis aimed to examine the temporal correlations between mean IQ scores from Standard Progressive Matrices and year of publication, moderated by types of countries and age groups covering seven decades (1948–2020). The given relationships were weighted by sample sizes. The dataset included 1038 independent samples (N = 299,155) from 72 countries. The results generally supported the FE with the IQ gain of 0.22 points per year, but the magnitudes of the IQ gains depended on types of countries and age groups. Stronger FEs were evident in middle-income countries and younger generations. A multicausal explanatory framework should be utilized to explain the underlying mechanism of the secular IQ gains across factors.

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.

Looking for Flynn effects in a recent online U.S. adult sample: Examining shifts within the SAPA Project

Compared to European countries, research is limited regarding if the Flynn effect, or its reversal, is a current phenomenon in the United States. Though recent research on the United States suggests that a Flynn effect could still be present, or partially present, among child and adolescent samples, few studies have explored differences of cognitive ability scores among US adults. Thirteen years of cross-sectional data from a subsample of adults (n = 394,378) were obtained from the Synthetic Aperture Personality Assessment Project (SAPA Project) to examine if cognitive ability scores changed within the United States from 2006 to 2018. Responses to an overlapping set of 35 (collected 2006–2018) and 60 (collected 2011–2018) items from the open-source multiple choice intelligence assessment International Cognitive Ability Resource (ICAR) were used to examine the trends in standardized average composite cognitive ability scores and domain scores of matrix reasoning, letter and number series, verbal reasoning, and three-dimensional rotation. Composite ability scores from 35 items and domain scores (matrix reasoning; letter and number series) showed a pattern consistent with a reversed Flynn effect from 2006 to 2018 when stratified across age, education, or gender. Slopes for verbal reasoning scores, however, failed to meet or exceed an annual threshold of |0.02| SD. A reversed Flynn effect was also present from 2011 to 2018 for composite ability scores from 60 items across age, education, and gender. Despite declining scores across age and demographics in other domains of cognitive ability, three-dimensional rotation scores showed evidence of a Flynn effect with the largest slopes occurring across age stratified regressions.

Are Movies Making Us Smarter?

Abstract IQ tests have charted massive gains over the last century, known as the Flynn Effect. Over the same period, the time society spends with screens has massively increased and intensified, for example, shorter and closer shots, increasing narrative complexity. In Movies on our Minds (2021), James Cutting suggests a potential bidirectional link between the two effects: generational increase in visual processing abilities led to movie makers increasing the demands their movies place on viewer cognition, which in turn has trained societal visual processing capacity. In this commentary we review the evidence for such a positive association. The evidence indicates that increasing screen time may be associated with faster visual processing but also a potentially decreased ability to process this information (i.e., reduced executive functions). Further, effects may be dependent on the type of screen experience (e.g., developmental appropriateness of content and delivery platform such as TikTok) and other environmental considerations (e.g., socioeconomic status, parenting), suggesting that the factors influencing our evolving media/mind niche may be more complex than originally proposed.

Reframing the clouded scientific spectacles of the Flynn effect: A view through two lenses

Flynn argued that the Flynn effect was due to an increasing use of “scientific spectacles” among the general population (Flynn, 2010), yet the Flynn effect itself has been viewed through clouded scientific spectacles. Most research has focused on Flynn's main finding: IQ scores have increased over time. Flynn (1987) presumed the effect was a cohort (generational) effect, yet a variety of within- and between-person processes could give rise to the observed secular changes. Many theories have been put forth as to the fundamental cause of the Flynn effect. Frequently ignored is what a specific cause implies the Flynn effect would look like at different levels of analysis and in the context of different research designs. In this paper we present two ‘lenses’ with which to view a potential causal model of the Flynn effect, in the hopes of closing some of the current gaps emerging from past research. First, we propose an examination of within- versus between-person processes. Relatedly, we propose that the exclusive focus on normed measures of intelligence has hampered understanding of what functional form the Flynn effect might take, particularly during development. Consideration of “raw” intelligence is likely to be fruitful. For our second lens, we consider the framework of age-period-cohort modeling to categorize what kind of effect a given model implies. We examine several causal theories of the Flynn effect through these lenses. Viewed through our lenses, we find that certain causal theories are, perhaps, somewhat incomplete in their specification of all the relevant processes.

The Evolution of Intelligence: Analysis of the Journal of Intelligence and Intelligence

What are the current trends in intelligence research? This parallel bibliometric analysis covers the two premier journals in the field: Intelligence and the Journal of Intelligence (JOI) between 2013 and 2022. Using Scopus data, this paper extends prior bibliometric articles reporting the evolution of the journal Intelligence from 1977 up to 2018. It includes JOI from its inception, along with Intelligence to the present. Although the journal Intelligence's growth has declined over time, it remains a stronghold for traditional influential research (average publications per year = 71.2, average citations per article = 17.07, average citations per year = 2.68). JOI shows a steady growth pattern in the number of publications and citations (average publications per year = 33.2, average citations per article = 6.48, total average citations per year = 1.48) since its inception in 2013. Common areas of study across both journals include cognitive ability, fluid intelligence, psychometrics-statistics, g-factor, and working memory. Intelligence includes core themes like the Flynn effect, individual differences, and geographic IQ variability. JOI addresses themes such as creativity, personality, and emotional intelligence. We discuss research trends, co-citation networks, thematic maps, and their implications for the future of the two journals and the evolution and future of the scientific study of intelligence.

The future of intelligence: A prediction of the FLynn effect based on past student assessment studies until the year 2100

In the 20th century, a strong increase in IQ test values was observed. However, the results of the last few decades point to an end to the FLynn effect or even its reversal. Scientists came to skeptical assumptions for the 21st century. There is hardly any research on the possible future development of intelligence. Here we present a statistical approach: Results from 24 student achievement surveys (TIMSS, PISA, PIRLS) from 1995 to 2019 serve as the data basis. In order to be included in the analysis, at least five measurements per country had to be available (N = 79 countries). For statistical estimation, trends (calculated via subtractions between measurements within one student survey approach), linear regressions and nonlinear quadratic regressions (both using any given student achievement data) were applied. A correction for outliers smoothed the results. For the sample of 79 countries, IQs would increase by about 10 IQ points by 2100 (international mean IQ 101). We compare the results with results from theoretical models. The theoretical models came to less optimistic conclusions. The results depend on the selected statistical (e.g., linear or nonlinear, outlier correction or not) and theoretical assumptions. We recommend that also other authors address this research question.

Effect of chemotherapy (with and without radiotherapy) on the intelligence of children and adolescents treated for acute lymphoblastic leukemia; a meta-analysis.

This meta-analysis assesses cognitive functioning in children with acute lymphoblastic leukemia post-treatment who were treated with either chemotherapy-only (CT-only) or in combination with radiation therapy (CTRT). The databases Pubmed and PsychInfo were searched between 1-1-2000and 31-12-2021. Data were analyzed using Comprehensive Meta-Analysis (version 2). Mean weighted intelligence after treatment was 100.2 (number of studies n=51, 95% CI: 98.8-101.5). For CT-only, it was 100.8 (95% CI: 99.5-102.2) and for CTRT 97.8 (95% CI: 95.9-100.2). Compared to recruited healthy controls, treated children had on average lower IQ scores (n=23, mean difference -7.8, 95% CI: -10.7 to -5.0, p<0.001). When looking only at studies using controls recruited from the patient's family, results remained significant (n=5, mean difference -6.0, 95% CI: -8.6 to -3.5, p=0.001). Meta-regressions aimed at identifying predictors of IQ after treatment failed to find an effect for sex or age. We could demonstrate an effect of time between diagnosis and IQ measurement for the CTRT treated patient (B=-0.26, 95% CI: -0.40 to -0.1, p=0.002). IQ scores of patients treated with CT-only or CTRT treatment regimens did not differ from the normative population. However, compared to recruited control groups, patients showed lower mean IQ scores. The Flynn effect and/or selection effects may play a role in this discrepancy. Considering time since diagnosis may have a significant impact on IQ, at least in CTRT treated patients, long-term clinical follow-up of neurocognitive development may be prudent to detect possible (late) neurocognitive effects.

Intelligence Differences across Years: A Trend Analysis

Flynn effect which advocated that there was a rise in the IQ score was widely accepted by the relevant scientific community. However, this effect has been reversed in recent years. In this study both Flynn and anti-Flynn effects were investigated. The purpose of this study is to determine the trend of students' general, verbal, and visual intelligence scores in the last 6 years (2016-2021). The participant of study included 2192 students who were first grade. To measure general, verbal, and visual intelligence of the participant, Anadolu-Sak Intelligence Scale (ASIS) was used. ASIS is the first intelligence test developed and standardized in Turkey. Participants’ mean of general, verbal, and visual intelligence scores in different years were compared by trend analysis. The research findings showed that there was a downward tendency in general, verbal, and visual scores between the years of 2016 to 2021. Moreover, our findings reveal that there is a sharp decrease between 2020 and 2021. Girls' GIQ, VIQ, and NIQ scores of 2021 showed a sharp decline compared to boys. As a result of this study, it can be said that the Flynn effect has gone into reversed.

FAMILY FLYNN EFFECTS AND LINKS TO MIDDLE-AGE HEALTH OUTCOMES

Abstract The Flynn effect (Flynn, 1984; 1987) refers to increases in cognitive performance, for later-born cohorts. It has been documented globally, occurring for more than a century. In a meta-analysis, Pietschnig and Voracek (2015) noted that the effect may be even stronger in adults than in children, though little research has addressed this topic (or its implications) for aging adults. Similarly, overall life-time health has improved, and incidences of cognitive impairment have decreased during the last two decades (Clouston et al., 2021). Using multilevel growth curve models, we found family Flynn effects in the National Longitudinal Survey of Youth; children in families with later-born mothers, and later-born first children, had higher PIAT math scores, and steeper developmental slopes. Although the link from childhood and adolescent cognitive function to later life outcomes has been well studied, research that takes advantage of the Flynn effect to facilitate interpreting that link is lacking. Clouston et al. (2021) emphasized the value of the Flynn effect in investigating links between childhood cognitive functioning and later adult Alzheimer’s disease and related dementia (ADRD) risks. We linked our family level results to middle-age maternal health outcomes (factors that are related to ADRD risks). Canonical correlation analyses showed that mothers (at ages 40+ and 50+) from families with higher score levels and slopes tended to have better mental and physical health. Our results, showing a Flynn effect in child and adolescence scores, at the family level, with links to adult health, persisted after controlling for a known selection bias.