County-level IQ and fertility rates: A partial test of Differential-K theory

Human intelligence (IQ) correlates with a number of important life outcomes ranging from mortality and morbidity to social rank and status. Noticeably absent from the literature, however, has been a unifying framework from which to examine why IQ should correspond to so many seemingly disparate outcomes. Rushton’s Differential-K theory represents a theoretical perspective capable of accounting for the role of IQ in understanding human flourishing. We tested predictions suggested by Differential-K theory by examining the association between IQ at the aggregate level and two life-history variables: parental investment and fertility rates. Our results provide tentative support for some of the predictions of Differential-K theory.     

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.     

Effects of Sesame Street: A meta-analysis of children's learning in 15 countries

Sesame Street is broadcast to millions of children globally, including in some of the world's poorest regions. This meta-analysis examines the effects of children's exposure to international co-productions of Sesame Street, synthesizing the results of 24 studies, conducted with over 10,000 children in 15 countries. The results indicated significant positive effects of exposure to the program, aggregated across learning outcomes, and within each of the three outcome categories: cognitive outcomes, including literacy and numeracy; learning about the world, including health and safety knowledge; social reasoning and attitudes toward out-groups. The effects were significant across different methods, and they were observed in both low- and middle-income countries and also in high-income countries. The results are contextualized by considering the effects and reach of the program, relative to other early childhood interventions.     

Identifying g: A review of current factor analytic practices in the science of mental abilities

Factor analysis is arguably one of the most important tools in the science of mental abilities. While many studies have been conducted to make recommendations regarding “best practices” concerning its use, it is unknown the degree to which contemporary ability researchers abide by those standards. The current study sought to evaluate the typical practices of contemporary ability researchers. We analyzed articles reporting factor analyses of cognitive ability tests administered to adult samples over a 12 year period. Results suggest that, in aggregate, the science of mental abilities seems to be doing well with respect to the issues of sample size, number of indicators (relative to number of factors) and breadth of indicators. Further, our results suggest that the majority of ability researchers are using methods of factor analysis that allow for the identification of a g factor. However, 14.57% failed to use a method that allowed a common factor to emerge. These results provide insights regarding the methodological quality of the science of mental abilities, and will hopefully encourage further “introspective” research into the science of mental abilities.     

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

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

The dependability of the general factor of intelligence: Why small, single-factor models do not adequately represent g

Floyd, Shands, Rafael, Bergeron and McGrew (2009) used generalizability theory to test the reliability of general-factor loadings and to compare three different sources of error in them: the test battery size, the test battery composition, the factor-extraction technique, and their interactions. They found that their general-factor loadings were moderately to strongly dependable. We replicated the methods of Floyd et al. (2009) in a different sample of tests, from the Minnesota Study of Twins Reared Apart (MISTRA). Our first hypothesis was that, given the greater diversity of the tests in MISTRA, the general-factor loadings would be less dependable than in Floyd et al. (2009). Our second hypothesis, contrary to the positions of Floyd et al. (2009) and Jensen and Weng (1994), was that the general factors from the small, randomly-formed test batteries would differ substantively from the general factor from a well-specified hierarchical model of all available tests. Subtests from MISTRA were randomly selected to form independent and overlapping batteries of 2, 4 and 8 tests in size, and the general-factor loadings of eight probe tests were obtained in each battery by principal components analysis, principal factor analysis and maximum likelihood estimation. Results initially indicated that the general-factor loadings were unexpectedly more dependable than in Floyd et al. (2009); however, further analysis revealed that this was due to the greater diversity of our probe tests. After adjustment for this difference in diversity, and consideration of the representativeness of our probe tests versus those of Floyd et al. (2009), our first hypothesis of lower dependability was confirmed in the overlapping batteries, but not the independent ones. To test the second hypothesis, we correlated g factor scores from the random test batteries with g factor scores from the VPR model; we also calculated special coefficients of congruence on the same relation. Consistent with our second hypothesis, the general factors from small non-hierarchical models were found to not be reliable enough for the purposes of theoretical research. We discuss appropriate standards for the construction and factor analysis of intelligence test batteries.     

Impulsivity,sensation seeking and reproductive behaviour: A life history perspective

Impulsivity has often been invoked as a proximate driver of different life-history strategies. However, conceptualisations of “impulsivity” are inconsistent and ambiguities exist regarding which facets of impulsivity are actually involved in the canalisation of reproductive strategies. Two variables commonly used to represent impulsivity were examined in relation to reproductive behaviour. Results demonstrated that sensation seeking was significantly related to strategy-based behaviour, but impulsivity (defined as a failure to deliberate) was only weakly correlated. The effect of impulsivity disappeared when sensation seeking was controlled. Sex differences emerged for sensation seeking but not impulsivity. We conclude that “impulsivity” is not a unitary trait and that clearer distinctions should be made between facets of this construct.     

On the myth and the reality of the temporal validity degradation of general mental ability test scores

Claims of changes in the validity coefficients associated with general mental ability (GMA) tests due to the passage of time (i.e., temporal validity degradation) have been the focus of an on-going debate in applied psychology. To evaluate whether and, if so, under what conditions this degradation may occur, we integrate evidence from multiple sub-disciplines of psychology. The temporal stability of construct validity is considered in light of the evidence regarding the differential stability of g and the invariance of measurement properties of GMA tests over the adult life-span. The temporal stability of criterion-related validity is considered in light of evidence from long-term predictive validity studies in educational and occupational realms. The evidence gained from this broad-ranging review suggests that temporal degradation of the construct- and criterion-related validity of ability test scores may not be as ubiquitous as some have previously concluded. Rather, it appears that both construct and criterion-related validity coefficients are reasonably robust over time and that any apparent degradation of criterion-related validity coefficients has more to do with changes in the determinants of task performance and changes in the nature of the criterion domain rather temporal degradation per se (i.e., the age of the test scores). A key exception to the conclusion that temporal validity degradation is more myth than reality concerns decision validity. Although the evidence is sparse, it is likely that the utility of a given GMA test score for making diagnostic decisions about an individual deteriorates over time. Importantly, we also note several areas in need of additional and more rigorous research before strong conclusions can be supported.     

Expanding the g-nexus: Further evidence regarding the relations among national IQ, religiosity and national health outcomes

The current study seeks to better understand how religiosity and health are positioned within the g-nexus. Specifically, the degree to which differences in average IQ across nations is associated with differences in national religiosity (i.e., belief rate) and national health statistics independent of differences in national wealth is examined. Consistent with expectations, results show that, independent of national wealth and belief rate, IQ has a positive influence on national health as indicated by fertility rate, infant mortality rate, maternal mortality rate, and deaths due to HIV/AIDS, and life expectancy. Additionally, as hypothesized, IQ and belief rate interacted to influence reproductive health (i.e., fertility rate, infant- and maternal mortality). Specifically, high IQ acts as a buffer against the negative effects of belief rate; when IQ is high belief rate has no effect, but when IQ is low belief rate has a strong negative effect. The pattern of findings from this study, combined with previous research, serve to confirm that general cognitive ability (i.e., the g-factor) is an important and central node within a larger nexus of psychological and social variables. Theoretical and epidemiological implications are discussed.     

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

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

In conversation with J. Philippe Rushton

The interview covers Rushton’s background in England, South Africa, and Canada, his education at the University of London (B.Sc., 1970; Ph.D., 1973), and his early research (1970–1980) on the social learning of generosity in 7- to 11-year olds. In his first book, Altruism, socialization, and society (1980), Rushton solved two “anomalies” for his social learning perspective—altruism in animals and traits in people—causing a “paradigm shift” for him toward sociobiology. He spent January to June 1981 at the University of California, Berkeley, to study the longitudinal stability of personality traits like altruism. There, he was influenced by Jensen’s work on g and race differences in rate of maturation and two-egg twinning. Subsequently, Rushton found that across 60 variables, Europeans fall between East Asians and Africans, closer to East Asians. He extrapolated Wilson’s (fast–slow) r-K life history theory to explain the pattern. Also covered is Rushton’s research on the heritability of altruism, and Genetic Similarity Theory explaining assortative mating and ethnic nepotism. Spouses and best friends are as similar as half-siblings and people randomly chosen from the same ethnic group are as related as first cousins. Altruism follows lines of similarity to replicate genes effectively. Rushton’s research on creativity is described.     

Strategic differentiation and integration among the 50 states of the USA

Recent studies demonstrate that individuals and populations (at the scale of nations) exhibiting slower life history (LH) speeds are more differentiated amongst themselves with respect to the components of life history. Faster life history individuals and populations are more integrated by comparison. This phenomenon, termed strategic differentiation–integration effort (SD–IE), has not yet been tested on a national scale, however, which is an important remaining step in establishing its generalizability at different levels of aggregation among humans. SD–IE was tested with data on five LH variables from the fifty states of the US. Effects supportive of the SD–IE hypothesis were found in all LH variables, with an average effect magnitude slightly larger than that found in studies of SD–IE at the individual differences level. This is putatively attributed to population stratification, due to the varied racial make-up of the population in the US, including European, African, Native American, and Asian ancestries from multiple countries. This study indicates that SD–IE is a generalizable phenomenon occurring at various levels of aggregation.     

Natural choice in chimpanzees (Pan troglodytes): Perceptual and temporal effects on selective value

In three experiments, four chimpanzees made choices between two visible food options to assess the validity of the selective value effect (the assignment of value to only the most preferred type of food presented in a comparison). In Experiment 1, we established that all chimpanzees preferred single banana pieces to single apple pieces before presenting the critical test. In this test two chimpanzees preferred a mix of one banana piece and one apple piece to a single banana piece when both banana pieces were approximately the same size, but two chimpanzees were indifferent between the two options, exhibiting the selective value effect. In Experiment 2, when the banana pieces in both options were more closely equated in size, the chimpanzees were biased to choose the single banana piece over the mixed array even though this was the smaller total amount of food. However, in Experiment 3, when we introduced longer intervals between each trial, the chimpanzees preferred the mixed set and thus the larger total amount of food. The results demonstrate that only some chimpanzees exhibit the choice pattern indicative of the selective value effect, and they do so only when item size is not carefully controlled and trials are presented quickly in succession. Thus, the behavior pattern originally labeled the selective value effect may actually be explained by a combination of chimpanzees’ sensitivity to small differences in preferred food amount and chimpanzees tendency to avoid less preferred foods that would delay the acquisition of further preferred food items.     

Politics, schadenfreude, and ingroup identification: The sometimes happy thing about a poor economy and death

Political campaigns are often characterized by the various events occurring that move the tide in favor of one candidate or another. Each event, depending on which candidate it favors or harms, produces either happiness or sadness for those who care about the outcome. This research examined whether such reactions would hold for events that are misfortunes for other people and even when they negatively affect society more broadly regardless of political party affiliation. Ingroup (i.e. political party) identification was examined as an important moderating variable. In four studies, undergraduate participants gave their emotional reactions to news articles describing misfortunes happening to others (e.g. poor economic news and house foreclosures). Party affiliation and the intensity of ingroup identification strongly predicted whether these events produced schadenfreude.     

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

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

Rushton’s r–K life history theory of race differences in penis length and circumference examined in 113 populations

 and r–K life history theory that Mongoloids are the most K evolved, Caucasoids somewhat less K evolved, and Negroids the least K evolved is examined and extended in an analysis of data for erect penis length and circumference in two new data sets. These new data extend Rushton’s theory by presenting disaggregated data for penis size for European and North African/South Asian Caucasoids; for East Asian and Southeast Asian Mongoloids; for Inuit and Amerindians and Mestizos, and for thirteen mixed race samples. The results generally confirm and extend Rushton’s r–K life history theory.     

Asparagus recemosus enhances memory and protects against amnesia in rodent models

Asparagus Racemosus (AR) is an Ayurvedic rasayana possessing multiple neuropharmacological activities. The adpatogenic and antidepressant activity of AR is well documented. The present study was undertaken to assess nootropic and anti-amnesic activities of MAR in rats. The Morris water maze (MWM) and elevated plus maze (EPM) models were employed to evaluate learning and memory activity. Subsequently, the anti-amnestic activity was evaluated in scopolamine and sodium nitrite (NaNO₂)-induced amnestic models in rats. Rats pre-treated with MAR (50, 100 and 200 mg/kg, p.o) for 7 days showed significant decrease in escape latency in the MWM test indicating nootropic activity. MAR also significantly reversed scopolamine and sodium nitrite-induced increase in transfer latency on EPM indicating anti-amnesic activity. Further, MAR dose-dependently inhibited acetylcholinesterase enzyme in specific brain regions (prefrontal cortex, hippocampus and hypothalamus). Thus, MAR showed nootropic and anti-amnesic activities in the models tested and these effects may probably be mediated through augmentation of cholinergic system due to its anti-cholinesterase activity.     

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.     

Spearman’s Law of Diminishing Returns and national ability

This research examined Spearman’s Law of Diminishing Returns (SLODR) using national ability as the unit of analysis. National ability was estimated using international standardized tests such as the Programme for International Student Assessment (PISA), Trends in International Mathematics and Science Study (TIMSS), and Progress in International Reading Literacy Study (PIRLS). Factor analysis estimated the national G loadings of tests for high and low ability nations. Consistent with SLODR, the G loadings of tests were lower for higher ability nations. The pattern was confirmed after correcting for school attendance and age biases. Because a test’s g loading is directly related to its predictive validity (correlation with outcomes), our results imply that the predictive validity of tests may be lower for higher ability nations.     

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.