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Poor children develop smaller brains than their richer classmates, according to two US studies. Neuroscientists who studied the brains of more than 100 young people found that the surface area of their cerebral cortex could be linked to family income.

The region of the brain studied is responsible for language, memory, spatial skills and reasoning. Columbia University found children in families that earned less than $25,000 ( £16,900) a year had surface areas six per cent smaller than those whose families earned $150,000 (£68,500) or more. ‘We’ve known for so long that poverty and lack of access to resources to enrich the developmental environment are related to poor school performance’, Elizabeth Sowell, of Children’s Hospital Los Angeles told the Washington Post.

‘But now we can really tie it to a physical thing in the brain. We realised that this is a big deal.’ Neuroscientists from MIT came to the same conclusion in a separate study. ‘Just as you would expect, there’s a real cost to not living in a supportive environment,’ said MIT’s John Gabrieli, a professor of brain and cognitive sciences.

‘To me, it’s a call to action. You want to boost the opportunities for those for whom it doesn’t come easily in their environment.’ While the study didn’t look at the possible reasons for differences in brain anatomy, previous research has found lower-income students are more likely to suffer from stress in early childhood.

This may be because they have more limited access to educational resources, and receive less exposure to spoken language early in life. The study included 58 students - 23 from lower-income families and 35 from higher-income families, all aged 12 or 13. Low-income students were defined as those who qualify for a free or reduced-price school lunch.

The researchers compared students’ scores on the Massachusetts Comprehensive Assessment System (MCAS) with scans showing the brain’s cortex. Using magnetic resonance imaging (MRI), they discovered differences in the thickness of parts of the cortex in the temporal and occipital lobes, whose primary roles are in vision and storing knowledge.

Those differences were linked to differences in both test scores and family income. In fact, differences in cortical thickness in these brain regions could explain as much as 44 per cent of the income achievement gap found in this study. In most other measures of brain anatomy, the researchers found no significant differences. The amount of white matter - the bundles of axons that connect different parts of the brain - did not differ, nor did the overall surface area of the brain cortex.

The researchers point out that the structural differences they did find are not necessarily permanent. ‘There’s so much strong evidence that brains are highly plastic,’ says Gabrieli, who is also a member of the McGovern Institute. ‘Our findings don’t mean that further educational support, home support, all those things, couldn’t make big differences.’ In a follow-up study, the researchers hope to learn more about what types of educational programs might help to close the achievement gap.