The brain structure of a feral ghoul indicates that the regenerative ability of the neurological system that affords "normal" necrotic post-humans their longevity does not extend into the higher reasoning functions of the brain itself. This condition is referred to as "ferocious post-necrotic dystrophy", according to the ghoul physician Barrows. Despite the apparent lack of the higher reasoning they once had as humans, some are capable of semi-intelligible speech, as the Vault 34 security officers will occasionally growl out understandable phrases similar to the trogs of The Pitt, meaning that their vocal chords are still relatively intact, as is the part of the brain which controls speech.
As the reasoning and critical thinking portions of a ghoul's brain deteriorate, the ghoul subject becomes increasingly hostile, giving in to a carnal need to feed. It remains unclear exactly what precipitates this change in neurobiology and psychology, but anecdotal evidence seems to indicate that non-social ghouls, or those in isolation, are more prone to the condition.
It is also quite possible that this is a gradual process, meaning that eventually all ghouls will succumb to this condition. However, considering the existence of ghouls that have been born prior to the Great War two centuries ago, it is quite possible that this theory is bunk, or that the rate of degeneration is dependent on the individual affected and surrounding environmental factors.
As with normal ghouls, ferals are not only extremely resistant to radiation, they are actually healed by it, as can be seen when a glowing one uses its' radiation blast nearby other ghouls. M.A.R.Go.T. also states that feral ghouls have no internal body heat.
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