When speaking of neural enhancement being distributed unfairly because of wealth inequality, it’s important to remember that even without drugs or prosthetics or engineering, we already have a similar playing field and that it’s very much divided into haves and have nots. Brain function, even size, is already influenced by poverty. From Chris Gyngell’s Practical Ethics post about a fictional brain-growing drug:

A new drug, Numarol, is currently being trialled which increases the surface area of the brain in children. Numarol causes children to have bigger brains, do better in cognitive tests and generally improves their life prospects. One critic of Numarol recently pointed out it would be very expensive, and only the rich would be able to afford it. Its release would likely create a significant difference in brain size between the highest and lowest socioeconomic groups. Numarol would create a world in which biological inequalities are forged from economic ones. The rich would not only have bigger houses, better cars, and better healthcare than the poor, their children would also have bigger brains. Such a world would be abhorrent.

But we already live in this world. Numarol is fictional, but the rich do have children with bigger brains than the poor. Social inequalities have already been written into our biology. 

This is the lesson from one of largest studies of brain morphology and structure in children. Brains of children from the lowest income bracket — less than US$25,000 — had up to 6% less surface area than those from children whose parental income was more than US$150,000. These differences in brain size where then found to be associated with differences in performance in a number of cognitive tests measuring working memory, vocabulary, and reading ability. These associations were independent of age, sex, parental education level and genetic ancestry (which was assessed through a whole genome analysis).

The relationship between family income and brain size was more pronounced among children in the poorest families where “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.”•