Prosopagnosia, also known as face blindness, is a cognitive disorder which limits an individual's ability to recognize human faces, including their own, while other aspects of visual processing and mental function remain unaffected.
It plays a major role in Nine Hours, Nine Persons, Nine Doors, as Gentarou Hongou has this condition and uses it as a partial motivation to create the First Nonary Game.
Types[]
Face recognition is primarily associated with the fusiform gyrus, a portion of the brain that reacts specifically to human faces. This allows a greater recognition of human faces than other visual stimuli, which in turn leads to the ability to distinguish people and associate them with other relevant memories (e.g. their names). In faceblind individuals this ability is impaired, meaning that they must rely on other cues to make these distinctions such as hair, gait, tattoos/piercings, and so on. Faceblind people often have to consciously memorize details of their peers in order to efficiently distinguish them.
Prosopagnosia can be categorized into two types: developmental and acquired. Developmental prosopagnosia is lifelong and may have a genetic component. Acquired prosopagnosia occurs as a result of lobe damage or other events that affect the brain.
Aquired prosopagnosia can also be divided into apperceptive and associative types. Apperceptive prosopagnosia limits the ability to make basic judgments with regards to faces, such as whether or not two faces, seen side by side, are the same. Associative prosopagnosia includes the ability to make some sense of faces, but a limited ability to make meaningful associations. People with associative prosopagnosia often report the experience of "knowing that they know" someone without being able to determine who they are, whereas people with apperceptive prosopagnosia generally struggle with even that much.
It is unclear which type of prosopagnosia Hongou has.
Nine Hours, Nine Persons, Nine Doors[]
Safe Ending[]
While in the Laboratory, Junpei and Lotus talk about the morphogenetic field as Lotus hacks a computer. Lotus mentions that it may be caused by diseases such as amnesia, aphasia, blindsight, and prosopagnosia. Junpei asks what prosopagnosia is and she describes it as being a condition which makes one be unable to recognize human faces.
Later in the Cargo room, Ace struggles with a simple puzzle which involves matching people's faces to a box with their number. Ace claims he is tired and cannot recognize the faces. Remembering what Lotus said, Junpei realizes Ace has prosopagnosia. However, he feels bad for Ace and decides to say nothing of it.
Later, after Clover and Snake are killed, Junpei realizes who their killer is. He tells Ace that he is Santa, but Ace calls him out on his lie. He asks why Ace believes he is Junpei and Ace says that it's because Junpei's bracelet is 5. Junpei finds this answer odd, as most people would simply say that they didn't have the same face. Junpei then publicly concludes that Ace has prosopagnosia. Ace reluctantly admits it.
Junpei then goes on to explain that he believes the killer has prosopagnosia, as Snake is not actually dead. This corpse is someone unknown. Junpei calls this man "Guy X". He further explains that the face blind killer was tricked into believing Guy X was Snake because Guy X was wearing Snake's clothes. Backed into a corner, Ace confesses to murdering them.
True Ending[]
Prosopagnosia is only mentioned in the Incinerator by Junpei after Ace talks about his condition. Junpei remembers that Ace has prosopagnosia from the Safe Ending because young Akane Kurashiki gives him that information. Ace also mentions his prosopagnosia during the First Nonary Game, by telling young Akane, "You don't know what it's like to spend every day surrounded by monkeys."