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SummaryThe aim of this study was to investigate the association between maternal sensitivity and offspring intelligence in late childhood and adolescence. Secondary data (N=117) from the Block and Block (2006a, b) 30-year longitudinal study of Californian children, which began in the late 1960s, was used to test the hypothesis that maternal sensitivity in childhood would be predictive of late childhood and adolescent intelligence. Correlational analyses revealed that maternal sensitivity, as judged by raters viewing mother's interactions with their children in a set of four joint structured cognitive tasks when the child was 5 years of age, was associated with verbal and performance IQ test scores when the children were ages 11 and 18. Using hierarchical regression to control for child sex, socioeconomic status, child temperament, child baseline IQ (as measured at age 4), mother's level of education and mother's emotional nurturance, it was found that the maternal sensitivity and child and adolescent IQ association held for verbal, but not performance IQ. Furthermore, a pattern emerged in which the association between maternal sensitivity and verbal IQ was stronger for adolescents with a lower baseline IQ. The results suggest that maternal sensitivity is associated with offspring verbal intelligence and that this association holds when numerous variables are accounted for. Additionally, this association may be stronger for children with lower IQs.

Using the continuous parameter estimation model (CPEM), a large genotyped adult sample of the population of Wisconsin, USA (the Wisconsin Longitudinal Study) is examined for evidence of the Scarr–Rowe effect, a gene × environment (G×E) interaction that reduces the heritability of IQ among those with low socioeconomic status (SES). This method allows the differential expressivity of polygenic scores predictive of both educational attainment and IQ (EA3) on the phenotype of IQ to be directly operationalized throughout the full range of these variables. Utilizing a parental SES factor-weighted composite as a measure of childhood SES, evidence for the Scarr–Rowe effect was found, that is, the genetic expressivity of EA3 on IQ increased with increasing parental SES (β = 0.08, p = 4.71×10−10, df = 6,255). The effect was found for both the male and female samples separately, β(males) = 0.08, p = 5.27×10−5, df = 3,018; β(females) = 0.08, p = 1.93×10−6, df = 3,236. The effects were furthermore robust to removing outlying values of parental SES and to log-transforming the SES variable. The results are similar to those produced using a more conventional two-way interaction model, with IQ predicting the EA3 × log of parental SES interaction after the main effects; however, CPEM allows for greater model degrees of freedom, thus is better powered to detect the effect when it is small in magnitude (CPEM β = 0.05, p = 6.69×10−5 vs. two-way interaction β = 0.02, pone-tailed = .045, in both models log parental SES is used).

There are indications that simple reaction time might have slowed in Western populations, based on both cohort- and multi-study comparisons. A possible limitation of the latter method in particular is measurement error stemming from methods variance, which results from the fact that instruments and experimental conditions change over time and between studies. We therefore set out to measure the simple auditory reaction time (SRT) of 7,081 individuals (2,997 males and 4,084 females) born in Sweden 1959–1985 (subjects were aged between 27 and 54 years at time of measurement). Depending on age cut-offs and adjustment for aging related slowing of SRT, the data indicate that SRT has increased by between 3 and 16 ms in the 27 birth years covered in the present sample. This slowing is unlikely to be explained by attrition, which was evaluated by comparing the general intelligence × birth-year interactions and standard deviations for both male participants and dropouts, utilizing military conscript cognitive ability data. The present result is consistent with previous studies employing alternative methods, and may indicate the operation of several synergistic factors, such as recent micro-evolutionary trends favoring lower g in Sweden and the effects of industrially produced neurotoxic substances on peripheral nerve conduction velocity.

There are indications that simple reaction time might have slowed in Western populations, based on both cohort- and multi-study comparisons. A possible limitation of the latter method in particular is measurement error stemming from methods variance, which results from the fact that instruments and experimental conditions change over time and between studies. We therefore set out to measure the simple auditory reaction time (SRT) of 7,081 individuals (2,997 males and 4,084 females) born in Sweden 1959-1985 (subjects were aged between 27 and 54 years at time of measurement). Depending on age cut-offs and adjustment for aging related slowing of SRT, the data indicate that SRT has increased by between 3 and 16 ms in the 27 birth years covered in the present sample. This slowing is unlikely to be explained by attrition, which was evaluated by comparing the general intelligence x birth-year interactions and standard deviations for both male participants and dropouts, utilizing military conscript cognitive ability data. The present result is consistent with previous studies employing alternative methods, and may indicate the operation of several synergistic factors, such as recent micro-evolutionary trends favoring lower g in Sweden and the effects of industrially produced neurotoxic substances on peripheral nerve conduction velocity.

Utilizing a newly released cognitive Polygenic Score (PGS) from Wave IV of Add Health (n = 1,886), structural equation models (SEMs) examining the relationship between PGS and fertility (which is approximately 50% complete in the present sample), employing measures of verbal IQ and educational attainment as potential mediators, were estimated. The results of indirect pathway models revealed that verbal IQ mediates the positive relationship between PGS and educational attainment, and educational attainment in turn mediates the negative relationship between verbal IQ and a latent fertility measure. The direct path from PGS to fertility was non-significant. The model was robust to controlling for age, sex, and race; furthermore, the results of a multigroup SEM revealed no significant differences in the estimated path coeficients across sex. These results indicate that those predisposed towards higher verbal IQ by virtue of higher PGS values are also predisposed towards trading fertility against time spent in education, which contributes to those with higher PGS values producing fewer offspring at this stage in their life course.

AbstractUsing newly available polygenic scores for educational attainment and cognitive ability, this paper investigates the possible presence and causes of a negative association between IQ and fertility in the Wisconsin Longitudinal Study sample, an issue that Retherford and Sewell first addressed 30 years ago. The effect of the polygenic score on the sample's reproductive characteristics was indirect: a latent cognitive ability measure, comprised of both educational attainment and IQ, wholly mediated the relationship. Age at first birth mediated the negative effect of cognitive ability on sample fertility, which had a direct (positive) effect on the number of grandchildren. Significantly greater impacts of cognitive ability on the sample's fertility characteristics were found among the female subsample. This indicates that, in this sample, having a genetic disposition toward higher cognitive ability does not directly reduce number of offspring; instead, higher cognitive ability is a risk factor for prolonging reproductive debut, which, especially for women, reduces the fertility window and, thus, the number of children and grandchildren that can be produced. By estimating the effect of the sample's reproductive characteristics on the strength of polygenic selection, it was found that the genetic variance component of IQ should be declining at a rate between −.208 (95% CI [−.020, −.383]) and −.424 (95% CI [−.041, −.766]) points per decade, depending on whether GCTA-GREML or classical behavior genetic estimates of IQ heritability are used to correct for 'missing' heritability.

AbstractThe Scarr–Rowe effect is a gene × environment interaction, which is characterized by a negative association between exposure to low socioeconomic status (SES) environments and the additive heritability of cognitive ability. Utilizing a polygenic score for educational attainment (EA3), it was found that the two-way interaction between EA3 and parental educational attainment (EA; used as a proxy for parental SES) was a significant positive predictor of participants' composite cognitive ability (IQ) score (β = .018, SE = .008, p = .028) after controlling hierarchically for the direct effects of (population-stratification-controlled) EA3, parental EA, and 20 distinct interaction terms (10 involving the interactions between the principal components [PCs] and EA3, and 10 involving the interaction between the PCs and parental EA). The presence of this interaction is consistent with the Scarr–Rowe effect, as the expressivity of EA3 on cognitive ability increases with increasing parental EA. No statistically significant sex differences in the effect magnitudes were found, although the effect was significantly present in the female but not male sample.

Intro -- Contents -- List of Figures -- List of Tables -- Chapter 1 Life History Theory: An Overview in Abstract -- References -- Part I Huntington, Crosby, and Baker -- Chapter 2 Ellsworth Huntington's Victorian Climatic Writings -- 1 Ellsworth Huntington's Climate-Colored Glasses -- 2 Mapping the Distribution of Civilization -- 3 Mapping the Distribution of Life History -- 4 The Life History Response to Eurasian Ecology -- References -- Chapter 3 Alfred W. Crosby: Adapting Within a Matrix of Flora and Fauna -- 1 The Walt Whitman of World History -- 2 The Columbian Exchange -- 3 Symbiotic Portmanteau Assemblages -- 4 Europeans and Amerindian Life Histories Before and After the Columbian Exchange -- References -- Chapter 4 The Historical Geography of Alan R. H. Baker: Scratching Out a Living After the Neolithic Revolution -- 1 The Historical Geography of A. R. H. Baker -- 2 Straddling the Divide -- 3 Baker in Life History Perspective -- 4 Support and Future Investigation -- References -- Part I Section Metacommentary -- References -- Part II Price, Malthus, and Landers -- Chapter 5 Richard Price: The Schedules of Mortality -- 1 Richard Price: Life and Works -- 2 Insuring Against Mortality -- 3 Intrinsic Versus Extrinsic Mortality -- 4 Comparative Evidence -- References -- Chapter 6 Thomas Robert Malthus, Stratification, and Subjugation: Closing the Commons and Opening the Factory -- 1 Scourge of the English Poor -- 2 Population Pressure -- 3 Population Density: A Driver of Life History Speed -- 4 Density-Dependent Life History Effects -- References -- Chapter 7 Famine, Pestilence, War, and Death: John Maxwell Landers' Four Horseman Spurring Humans Faster Along the Life History Continuum -- 1 The Historical Evolution of Urban Populations -- 2 Fertility, Infection, Technology, War, and Death.

In various personality models, such as the Big Five, a consistent higher order general factor of personality (GFP) can be identified. One view in the literature is that the GFP reflects general social effectiveness. Most GFP studies, however, have been conducted in Western, educated, industrialized, and rich democracies (WEIRD). Therefore, to address the question of the universality of the GFP, we test whether the GFP can also be identified in a preliterate indigenous sample of Tsimane by using self-reports, spouse reports, and interviewer ratings. In the Tsimane, a viable GFP could be identified and the intercorrelations between personality traits were significantly stronger than in samples from industrial countries. The GFP correlated with the ratings of social engagement. In addition, self and spouse ratings of the GFP overlapped. Overall, the findings are in line with the notion that the GFP is a human universal and a substantive personality factor reflecting social effectiveness.

In various personality models, such as the Big Five, a consistent higher order general factor of personality (GFP) can be identified. One view in the literature is that the GFP reflects general social effectiveness. Most GFP studies, however, have been conducted in Western, educated, industrialized, and rich democracies (WEIRD). Therefore, to address the question of the universality of the GFP, we test whether the GFP can also be identified in a preliterate indigenous sample of Tsimane by using self-reports, spouse reports, and interviewer ratings. In the Tsimane, a viable GFP could be identified and the intercorrelations between personality traits were significantly stronger than in samples from industrial countries. The GFP correlated with the ratings of social engagement. In addition, self and spouse ratings of the GFP overlapped. Overall, the findings are in line with the notion that the GFP is a human universal and a substantive personality factor reflecting social effectiveness.