How does that happen? The researchers haven't figured that out yet, but one study looked at the brains of 1,099 children, adolescents and young adults in various US cities, and then mapped each child’s genetic ancestry to adjust for differences in brain structure variations among ethnic groups.
The brains of children from the lowest income bracket — less than US $25,000 — had up to 6% less surface area than did those of children from families making more than US $150,000, the researchers found. In children from the poorest families, income disparities of a few thousand dollars were associated with major differences in brain structure, particularly in areas associated with language and decision-making skills. Children's scores on tests measuring cognitive skills, such as reading and memory ability, also declined with parental income.
Another study looked at 55 African-American girls in Philadelphia at age one month.
Even at this early age, the researchers found, infants in the lower socioeconomic brackets had smaller brains than their wealthier counterparts.
Genetic factors may be involved, but pre-natal environmental exposure to stress and nutrition may be just as likely. This variable, called epigenetics, can be passed down in DNA if poor environmental factors are not halted.
Can the impact be reversed through nutrition? Possibly, and that's what researchers wish to focus on next.