Suchergebnisse

SummaryWicherts (2018) criticizes the use of the method of correlated vectors when testing Spearman's hypothesis. It is argued that Wicherts ignores the psychometric meta-analytic method of correlated vectors hybrid model and so is attacking a strawman.

Evidence from eleven samples indicates that the mean IQ of third world immigrants in the Netherlands is lower than the Dutch mean by approximately one standard deviation for Surinamese and Antillians, and by approximately one and a half standard deviations for Turks and Moroccans. Since IQ tests provide the best prediction of success in school and organizations, it could be that the immigrants' lower mean IQ is an important factor in their low status on the Dutch labour market. The IQs of second-generation immigrants are rising.

SummaryThe study focused on the extent to which the general factor of intelligence g and heritability coefficients of the subtests of an IQ battery correlate. Modest to strong positive correlations were found in five studies from Western countries and six studies from a Japanese meta-analysis. The results for Russian twins were compared with those of the Western and Japanese studies. Data from 402 twins aged 13 and 296 twins aged 16 showed correlations of r=−0.45 and r=−0.60, respectively. It is concluded that the two data points are clearly not in line with established findings. It may be that the link between g loadings and heritabilities is more complex than previously thought.

AbstractA test of Jensen effects is of nil value as a diagnostic instrument when various good-sized meta-analyses show Jensen effects appear for both genetic effects and environmental effects. Using thought experiments, Flynn (2019) claims that some schooling gains yield Jensen effects, which should not be the case for an environmental effect. However, a meta-analysis (K = 12, total N = 60,993, mean r = 0.13) of schooling gains shows no Jensen effect. Real data trump thought experiments, so it is concluded there is no empirical proof of anomalous Jensen effects for schooling gains.

SummarySpearman's hypothesis tested at the level of items states that differences between ethnic groups on the items of an IQ test are a function of thegloadings of these items, such that there are small differences between ethnic groups on items with lowgloadings and large differences between ethnic groups on items with highgloadings; this has been confirmed in a limited number of studies. In this paper, Spearman's hypothesis was tested, comparing a group of Saudi children and adolescents (N=3209) with other groups of children and adolescents from Denmark, Cyprus, Croatia, Bosnia, South Africa, Estonia, Ukraine, Ireland, Russia and Chile (totalN=9333). The analyses were carried out on twelve comparisons between the Saudi Arabian children and the other children. Spearman's hypothesis was confirmed less strongly than in other large-scale studies with a mean weightedrvalue of 0.44. The relevance of these findings for the discussion on the causes of group differences is discussed.