The boy's intelligence grew naturally, without impediment. Only his motor facilities seemed impaired. Problems in the womb had caused it not to develop. The general view is that the cerebellum acts as the brains quality control centre allowing for learned behaviour to continue. In the cerebellum copies of actions are retained-jumping over a fence, writing, typing, running. The relevant article, The Economist December 22nd 2018, suggests that his family acting as part of his mind that was missing, showing him how to walk and making sure he did, allowed for his gradual progress-now he can walk, run and play.
Is it possible that our brains do not function independently, that it is simply a myth we hold to, and that the community, family and society supplies our behaviour, even the most simple things. I think the imagined independence of the brain, individuality and separation from the community that occasions ego is illusion, that the development of each brain depends on many others.
This is an old concept that has been forgotten or half forgotten after a century of psychoanalytical ideas, reductionist biological approaches, as the article says-a process of internalised automation takes place and the sense of self emerges (me) with maturation and the separation from early producers of internalised automation.
In the boy's case his basal ganglia (where habits are enforced) has also taken over some of the slack. Again this provides evidence for the construction of personality through roles (Sartre).
The boy still struggles and his motor skills do not function efficiently but he is getting there.