One of the many visual pieces of evidence that parental socio-economic status does NOT determine a child’s IQ: In Sweden, there’s a clear correlation between children’s IQ and their parents’ level of education for biological children, but no such correlation for adopted children. If family environment and parental social status explained IQ, the same relationship would hold for adopted children as well. This shows that the correlation between IQ and parental education among biological children is actually explained by the parents’ genes, not their environment.