How Reliably Can We Measure a Child's True IQ? Socio-Economic Status Can Explain Most of the Inter-Ethnic Differences in General Non-verbal Abilities.

Roma children have been discriminated against for many years as they are denied access to high-quality education based on their scores on general non-verbal IQ tests. Rushton et al. (2007) showed that Roma perform more poorly than non-Roma on one such test (i.e., Raven Progressive Matrices), but suggest that this underperformance could be explained by Roma's low socio-economic status. In this paper, we tested the non-verbal abilities of Roma children and expanded on the research of Rushton et al. (2007) by investigating empirically the potential mediating effects of socio-economic status on children's performance on Raven Progressive Matrices. Results showed that the performance of Roma children was, on average, significantly lower than the performance of their non-Roma peers; however, the effect of ethnicity was partially mediated by the parents' education and living conditions (while the parents' income had no significant effect). As hypothesized by Rushton et al. (2007) some socio-economic factors can explain important variability in the performance of Roma children on general non-verbal tests, and their poor performance on such tests may lead to an underestimation of the true population mean.

Socioeconomic background, nonverbal IQ and school absence affects the development of vocabulary and reading comprehension in children living in severe poverty.

Few studies have examined how socioeconomic status (SES) affects two essential parts of human development, namely vocabulary and reading comprehension, in children facing severe poverty. The Roma population is the largest minority group in Europe, the majority of whom live in severe poverty. This study compared the development of 322 Roma children with the development of 178 non-Roma children, between the ages of 7 and 10 years, living in Romania. The Roma children had poorer initial vocabulary and reading comprehension skills as well as slower growth rates for both compared to the non-Roma children. Importantly, SES had a direct influence on growth in both reading comprehension and vocabulary. The effect of SES was partly mediated by school absence and nonverbal IQ. This is a powerful finding since it suggests that poverty may have detrimental effects not only on reading but also on the development of verbal abilities.