Mind-shriek

The stunted mind produces shrill, discordant thoughts. An external observer may spot the occasional, inappropriate giggle, the non-sensical statement, the never-finished sentences. Other signs are noisy arguments without object, shifty eyes, harsh cries of anger, swearing outbursts, cliché-filled babble.

The incompetent mind feels so threatened by the universe and by the presence of other people that it caterwauls in its silent chamber, and incontinently emits bizarre, human-like noise via the mouth.