Overview of the Flynn effect

Following WW2, various researchers found and reported secular gains in IQ, but it was not until additional reports appeared in the 1980s that researchers began to look for the cause or causes. It was quickly apparent that the gains were not limited to any group or nation, but the manifestation of the gains was different depending on time and place. For every discovery, there was a different or opposite result in a different data set. Gains have been large, small, variable, and even negative. Some researchers have found that the gains were on g, while more have found no g loading. Abstract test formats, such as the Raven have often shown the greatest gains, but gains have also appeared in tests of crystallized intelligence. Some data has shown greater gains for the lower half of the intelligence distribution, while others have shown greater gains in the top half, and others have shown equal gains at all levels. Hypotheses for the causes have included environmental factors, genetic effects, reduced fertility, and methodological dependence. Two models are discussed.     

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.     

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.     

The Flynn effect puzzle: A 30-year examination from the right tail of the ability distribution provides some missing pieces

The Flynn effect is the rise in IQ scores across the last eighty or more years documented in the general distribution of both industrialized and developing nations primarily on tests that require problem solving and non-verbal reasoning. However, whether the effect extends to the right tail (i.e., the top 5% of ability) remains unknown. The present study uses roughly 1.7 million scores of 7th-grade students on the SAT and ACT as well as scores of 5th- and 6th-grade students on the EXPLORE from 1981 to 2010 to investigate whether the effect operates in the right tail. The effect was found in the top 5% at a rate similar to the general distribution, providing evidence for the first time that the entire curve is likely increasing at a constant rate. The effect was also found for females as well as males, appears to still be continuing, is primarily concentrated on the mathematics subtests of the SAT, ACT, and EXPLORE, and operates similarly for both 5th and 6th as well as 7th graders in the right tail. These findings help clarify the nature of the effect and may suggest ways that potential causes can now be more meaningfully offered and evaluated.     

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.     

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.     

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.     

Mix me a list: Context moderates the truth effect and the mere-exposure effect

When participants are repeatedly presented with an unfamiliar stimulus, this stimulus is rated as more likable (mere-exposure effect) or more valid (truth effect) as compared with a similar non-repeated stimulus. Both effects have been discussed as effects of fluency. Typical research designs on these effects involve a test phase in which ratings of both repeated and non-repeated stimuli are required. Based on research on moderators of fluency effects, we propose that the procedure of assessing the effects with mixed lists of repeated and non-repeated stimuli contributes strongly to the emergence of both effects. Two experiments found that the truth effect and the mere-exposure effect were strongly moderated by whether mixed lists or only repeated items were used at the test phase: whereas strong effects occurred in a context of repeated and non-repeated stimuli, the effects vanished with only repeated stimuli. Methodological and theoretical implications are discussed.     

Reading is believing: the truth effect and source credibility

Five experiments explored how source reliability influences people’s tendency to rate statements as more credible when they were encountered earlier (the truth effect). Undergraduates read statements from one reliable source and one unreliable source. Statements read multiple times were perceived as more valid and were more often correctly identified on a general knowledge test than statements read once or not at all. This occurred at varying retention intervals whether the statements originated from a reliable or unreliable source, when people had little memory for the statements themselves or their source, and when the discrediting information about the sources came either before or after reading the facts. While repetition aided recognition and source accuracy, both were unaffected by the reliability of the source. Consistent with the source monitoring framework, familiarity may create an illusion of truth for statements when people lack source-specifying cues, especially cues regarding the reliability of the source.     

The enhanced Simon effect for older adults is reduced when the irrelevant location information is conveyed by an accessory stimulus

The Simon effect, better performance when irrelevant stimulus location corresponds with the response location than when it does not, typically is larger for older than younger adults. However, Simon and Pouraghabagher [Simon, R. J., & Pouraghabagher, A. R. (1978). The effect of aging on the stages of processing in a choice reaction time task. Journal of Gerontology, 33, 553-561] found no age difference using an accessory-stimulus Simon task in which the relevant dimension was the color of a visual stimulus and the irrelevant dimension the location of a tone. Experiment 1 confirmed that older adults show a larger Simon effect than younger adults for the visual Simon task and that this age-related deficit is reduced or eliminated for the auditory-accessory task. Experiment 2 provided evidence suggesting that a small part of the age-related deficit in the visual Simon task is due to having to code the location of the relevant stimulus, but Experiment 3 showed that the majority of the deficit is due to the relevant and irrelevant information being conveyed by the same stimulus. Reaction-time distribution analyses show similar functions for younger and older adults, suggesting that the time course of activation is similar for both age groups.     

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 implicit sense of agency is not a perceptual effect but is a judgment effect

Cognitive Processing - The sense of agency (SoA) is characterized as the sense of being the causal agent of one's own actions, and it is measured in two forms: explicit and implicit. In the...     

The picture-word interference effect is not a Stroop effect

A psychological refractory period (PRP) paradigm was used to isolate the locus of the picture-word interference effect along the chain of processes subtended in name production. Two stimuli were presented sequentially on each trial, separated by a varying stimulus onset asynchrony (SOA). The first stimulus, SI, was a tone that required a manual response. The second stimulus, S2, was a picture-word stimulus associated with picture naming. The distractor word was conceptually related to the picture on half of the trials, and unrelated in the other trials. A picture-word interference effect was found at long SOA, but not at short SOA. Such underadditive interaction between SOA and semantic relatedness suggests strongly that the locus of the picture-word interference effect is functionally earlier than the PRP effect locus. The results are discussed in relation to models of word production suggesting the involvement of central mechanisms in the selection of lexical output.     

There is no clam with coats in the calm coast: Delimiting the transposed-letter priming effect

In this article, we explore the transposed-letter priming effect (e.g., jugde–JUDGE vs. jupte–JUDGE), a phenomenon that taps into some key issues on how the brain encodes letter positions and has favoured the creation of new input coding schemes. However, almost all the empirical evidence from transposed-letter priming experiments comes from nonword primes (e.g., jugde–JUDGE). Indeed, previous evidence when using word–word pairs (e.g., causal–CASUAL) is not conclusive. Here, we conducted five masked priming lexical decision experiments that examined the relationship between pairs of real words that differed only in the transposition of two of their letters (e.g., CASUAL vs. CAUSAL). Results showed that, unlike transposed-letter nonwords, transposed-letter words do not seem to affect the identification time of their transposed-letter mates. Thus, prime lexicality is a key factor that modulates the magnitude of transposed-letter priming effects. These results are interpreted under the assumption of the existence of lateral inhibition processes occurring within the lexical level—which cancels out any orthographic facilitation due to the overlapping letters. We examine the implications of these findings for models of visual-word recognition.     

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.     

In search of a strong visual recency effect

When a sequence of visual stimuli is presented in a fixed location, immediate serial recall of the sequence is characterized by only a small recency effect. According to Battacchi, Pelamatti, and Umiltà (1990), the distribution of visual stimuli over space, as well as time, greatly enhances the recency effect. After an initial failure to find a strong visual recency effect with distributed presentation (Experiment 1), in the remaining experiments an attempt was made to more closely approximate Battacchi et al.'s methodology by eliminating articulatory suppression (Experiments 2-7), using their stimuli (Experiments 3-7), blocking conditions (Experiments 4-7), requiring written rather than typed responses (Experiments 5-7), and using their list length (Experiments 6 and 7). Nevertheless, even when their method was followed as closely as possible (Experiment 7), distributed presentation did not produce a strong visual recency effect. The influence of distributed presentation on the visual recency effect would seem to be, at best, limited.