The measurement of Human Life History strategy

This retrospective essay appraises J. Philippe Rushton’s application of life history to understanding the covariation among human traits in light of subsequent developments in the measurement and latent structure of Human Life History, covitality, and personality. We conclude that Rushton should be recognized for having initiated a theoretically and empirically highly fertile paradigm in human individual differences research.     

Global behavioral variation: A test of differential-K

Despite Rushton’s path-breaking work into evolutionary forces affecting life history traits, not many attempts at operationalizing the differential-K spectrum at the level of countries or racial groups have been made so far. We report the construction of a “national K” factor from country-level behavioral variables. This K factor is closely related to country-level intelligence (“g”), operationalized by a composite score of IQ and scholastic achievement. We further demonstrate relationships of both g and K with measures of current environment and hypothesized evolutionary antecedents. Whereas K is predicted most powerfully by intelligence, log-transformed GDP (lgGDP) and skin reflectance, g is predicted by skin reflectance, lgGDP, cranial capacity, and a measure of evolutionary novelty.     

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.     

Are cognitive differences between countries diminishing? Evidence from TIMSS and PISA

Cognitive ability differences between countries can be large, with average IQs ranging from approximately 70 in sub-Saharan Africa to 105 in the countries of north-east Asia. A likely reason for the great magnitude of these differences is the Flynn effect, which massively raised average IQs in economically advanced countries during the 20th century. The present study tests the prediction that international IQ differences are diminishing again because substantial Flynn effects are now under way in the less developed “low-IQ countries” while intelligence is stagnating in the economically advanced “high-IQ countries.” The hypothesis is examined with two periodically administered scholastic assessment programs. TIMSS has tested 8th-grade students periodically between 1995 and 2011 in mathematics and science, and PISA has administered tests of mathematics, science and reading between 2000 and 2009. In both TIMSS and PISA, low-scoring countries tend to show a rising trend relative to higher-scoring countries. Despite the short time series of only 9 and 16 years, the results indicate that differences between high-scoring and low-scoring countries are diminishing on these scholastic achievement tests. The results support the prediction that through a combination of substantial Flynn effects in low-scoring countries and diminished (or even negative) Flynn effects in high-scoring countries, cognitive differences between countries are getting smaller on a worldwide scale.     

Problematic constructs and cultural-mediation: A comment on Heaven, Ciarrochi and Leeson (2011)

A recent study [Heaven, Ciarrochi & Leeson, (2011). Cognitive ability, right-wing authoritarianism, and social dominance orientation: A five-year longitudinal study amongst adolescents. Intelligence, 39, 15-21] finds evidence that amongst an Australian student sample, low g and verbal ability are predictive of Right Wing Authoritarianism (RWA) and that low verbal ability is predictive of Social Dominance Orientation (SDO). They speculate that those high on RWA might expend little effort in information processing, exhibit simplified judgments and (in the case of SDO) possess lower social competence. RWA and SDO are primarily measures of attitudes and it is known that explicit attitudes can be wholly at variance to implicit orientations. The finding is reinterpreted in light of the cultural-mediation hypothesis, whereby high-IQ individuals possessing flexible and adaptable personalities explicitly process the political and social attitudes that best resonate with culturally constructed norms. It is concluded that the cultural-mediation hypothesis should be the default hypothesis in explaining the direction of the correlation between IQ and political orientation. Only when potential cultural mediators have been ruled out should other hypotheses be considered.     

Is collective intelligence (mostly) the General Factor of Personality? A comment on Woolley,Chabris, Pentland,Hashmi and Malone (2010)

A recent paper [Woolley, Chabris, Pentland, Hashmi, & Malone. (2010). Evidence for a collective intelligence factor in the performance of human groups. Science, 330, 686–688] presents evidence for the existence of a general collective intelligence factor, ‘c,’ which may undergird performance on a variety of group tasks. This factor appears to be only modestly correlated with the average and maximum intelligence of group members whilst being more strongly correlated with the average social sensitivity of group members, a tendency for several members to contribute to group conversations rather than a small number dominating the discussions, and the proportion of females in the group. An alternative hypothesis, not considered by the authors, is that the General Factor of Personality (GFP) is able to account for the correlates of c observed, and that c may therefore be primarily a group level manifestation of the GFP, with a subordinate contribution from general intelligence. We maintain that a consideration of the GFP and its correlates as potential confounding variables would be of considerable benefit to future research into collective intelligence.     

Heterosis doesn't cause the Flynn effect: a critical examination of Mingroni (2007)

Mingroni (2007) proposed that heterosis or hybrid vigor may be the principal driver of the Flynn effect--the tendency for IQ scores to increase at a rate of approximately 3 points per decade. This model was presented as a resolution to the IQ paradox--the observation that IQ scores have been increasing despite their high adult heritability--on the basis that substantial changes in IQ can only be accounted for by changes in underlying genetic factors. It is here argued that this model is predicated upon a misconception of the Flynn effect, which is most pronounced on the least g-loaded components of cognitive ability tests and is uncorrelated with genetic effects such as inbreeding depression scores (which are correlated with the g loadings of tests). Evidence supportive of the recently proposed life history model of the Flynn effect is presented. In the discussion, other theoretical objections to the heterosis model are also considered. On this basis, it is concluded that the Flynn effect is strongly entwined with developmental status and that heterosis cannot be its principal cause.     

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.