The most complex functions, which are acquired last, are the first to show impairment.
In cases of general degeneration, softening of the brain, etc., the intelligence and moral nature are first affected, then memory, association, and acquired actions of all sorts, while there remain, latest of all, actions of the imitative kind, most of the deep-set habits, and the instinctive, reflex, and automatic functions, This last condition is seen in the wretched victim of dementia and in the congenital idiot.

The latter has, in addition to his life processes and instincts, little more than the capacity for parrot-like imitation.

By this he acquires the very few items of his education.
The recovery of the patient shows the same stages again, but in the reversed direction; he pursues the order of the original acquisition, a process which physicians call Re-evolution..