The distinctions were most profound in regions of the brain supporting language and reading, executive functions like memory and decision-making, and spatial skills, experts in the United States reported in the journal Nature Neuroscience.
The impact was “meaningful in terms of the way the brain is working in these kids”, study co-author Elizabeth Sowell of the University of Southern California told AFP.
“We found that the relationship between brain (structure) and family income impacted kids’ cognitive functioning,” Sowell said by email.
The study stressed that solutions lay within reach, including better school lunches, motivated teaching and community programmes to encourage children.
“It is not too late to think about how to impact resources that enrich the developmental environment, that in turn help the brain wire itself together,” Sowell said.
Socioeconomic inequalities have long been seen as linked to differences in cognitive development, but the extent to which it affected brain structure was unclear until now.
In what is claimed to be the biggest study of its kind, Sowell’s team tested 1,099 typically developing boys and girls aged three to 20, from diverse population groups.
They compared parents’ income and education level to children’s brain surface area, measured by scans, as well as their cognitive test scores.
They corrected for other potentially confounding influences on brain structure such as genetic ancestry.
Aside from the differences observed between the brain surface area of children in the lowest and highest income levels, there was also a striking disparity between income groups at the lower end of the scale.
There was a bigger difference, for example, between the results in kids from families earning either $30,000 (28,000 euros) or $50,000 per year, than those earning either $90,000 or $110,000.
Sowell said the reason behind that difference was unclear.
“It seems reasonable to speculate that resources afforded by the more affluent (nutrition, child care, schools etc) help ‘wire’ the brain through development,” she said.
“The most important point we want to convey… is not ‘if you are poor, your brain will be smaller, and there is nothing that can be done about it.’ That is absolutely not the message!”