In a new study out in Intelligence, Sophie von Stumm and Robert Plomin showed that children from high socioeconomic status families (SES) scored about 6 IQ points better than low SES children age 2 and that, in addition, this early difference had tripled by the time that children reached 16 years of age.

Data were analysed from 14,853 children and their parents, who are part of the Twins Early Development Study (TEDS) – the world’s largest study on cognitive development in children.

SES was positively associated with both the starting point in IQ and IQ gains over time. That is, children from more advantaged family backgrounds scored better at age 2 on IQ, and they also experienced greater IQ gains over time up to age 16 compared to children from low SES backgrounds.

Here’s the figure that summarizes the study’s findings:

Lines refer to latent growth curve trajectories. Dots represent the IQ raw means. High SES (triangles) refers to children, whose family SES was at least 1 SD above the SES mean; low SES (squares) refers to children from families who scored 1 SD below the SES mean. Medium SES (dots) includes all children, whose families were between -1 and +1 SD of SES.

Lines refer to latent growth curve trajectories. Dots represent the IQ raw means. High SES (triangles) refers to children, whose family SES was at least 1 SD above the SES mean; low SES (squares) refers to children from families who scored 1 SD below the SES mean. Medium SES (dots) includes all children, whose families were between -1 and +1 SD of SES.