This travels into the brain along an optic nerve (there is one for each eye) to arrive at one of two small clusters of nerve cells called the lateral geniculate bodies.
His conclusion is that the main difference is in the structure of the small columns of nerve cells that are packed together to form the cerebral cortex.
That commute became a test of nerve and savvy for the small group of children from the neighborhood who would try to anticipate gang hot spots and avoid them for fear of attack.