MIT researchers found that lower-income students have thinner brain cortexes compared to those from higher-income families (Washington Post version). This difference correlated with performance on standardized tests.

While the study didn't examine possible causes, previous research shows that children in lower-income families experience greater stress during childhood development. They also are exposed to less language and educational resources. All these are likely causes for reduced brain development.

The study was based on MRI brain imaging (a technique that's both slow and expensive) and consequently had a relatively low n, or number of subjects: 23 from lower-income families and 35 from higher-income families (all 12 - 13 years old). Given that number, verifying studies will be good but I'm pretty confident this trend will be reproducible. As Dr. John Gabrieli, an author of the study and professor of brain and cognitive sciences at MIT summarized: “Just as you would expect, there’s a real cost to not living in a supportive environment. We can see it not only in test scores, in educational attainment, but within the brains of these children.” None of this is surprising.

My gut says this is less a function of income and more about time, which lower-income workers have less of, at least measured by sleep.

With the pace of life today, it's hard but my take-away on this is to make time for your kids, explain things to them (actually just talking to them all the time is really good), do stuff with them and try to answer their questions. Even if you don't know the activity or question, they learn from our approaches. Making your kids smarter is worth the time.