“The Uncanny Valley hypothesis holds that when robots and other facsimiles of humans look and act almost like actual humans, it causes a response of revulsion among human observers. The “valley” in question is a dip in a proposed graph of the positivity of human reaction as a function of a robot’s lifelikeness.

It was introduced by Japanese roboticist Masahiro Mori in 1970, and has been linked to Ernst Jentsch’s concept of “the uncanny” identified in a 1906 essay, “On the Psychology of the Uncanny”. Jentsch’s conception is famously elaborated upon by Sigmund Freud in a 1919 essay titled “The Uncanny” (“Das Unheimliche”).”

Possible theories for your kindest consideration!

* Mate selection. Automatic, stimulus-driven appraisals of uncanny stimuli elicit aversion by activating an evolved cognitive mechanism for the avoidance of selecting mates with low fertility, poor hormonal health, or ineffective immune systems based on visible features of the face and body that are predictive of those traits.

* Mortality salience. An “uncanny robot elicits an innate fear of death and culturally-supported defenses for coping with death’s inevitability…. [P]artially disassembled androids… play on subconscious fears of reduction, replacement, and annihilation: (1) A mechanism with a human facade and a mechanical interior plays on our subconscious fear that we are all just soulless machines. (2) Androids in various states of mutilation, decapitation, or disassembly are reminiscent of a battlefield after a conflict and, as such, serve as a reminder of our mortality. (3) Since most androids are copies of actual people, they are Doppelgaenger and may elicit a fear of being replaced, on the job, in a relationship, and so on. (4) The jerkiness of an android’s movements could be unsettling because it elicits a fear of losing bodily control.”

* Pathogen avoidance. Uncanny stimuli may activate a cognitive mechanism that originally evolved to motivate the avoidance of potential sources of pathogens by eliciting a disgust response. “The more human an organism looks, the stronger the aversion to its defects, because (1) defects indicate disease, (2) more human-looking organisms are more closely related to human beings genetically, and (3) the probability of contracting disease-causing bacteria, viruses, and other parasites increases with genetic similarity.” Thus, the visual anomalies of android robots and animated human characters have the same effect as those of corpses and visibly diseased individuals: the elicitation of alarm and revulsion.

* Sorites paradoxes. Stimuli with human and nonhuman traits undermine our sense of human identity by linking qualitatively different categories, human and nonhuman, by a quantitative metric, degree of human likeness.

* Violation of human norms. The uncanny valley may “be symptomatic of entities that elicit a model of a human other but do not measure up to it.” If an entity looks sufficiently nonhuman, its human characteristics will be noticeable, generating empathy. However, if the entity looks almost human, it will elicit our model of a human other and its detailed normative expectations. The nonhuman characteristics will be noticeable, giving the human viewer a sense of strangeness. In other words, a robot stuck inside the uncanny valley is no longer being judged by the standards of a robot doing a passable job at pretending to be human, but is instead being judged by the standards of a human doing a terrible job at acting like a normal person.

* Western constructions of human identity. The existence of artificial but humanlike entities is a threat to human identity as socially constructed in the West and the Middle East but not in the Far East, partly because Western philosophy and religions (e.g., Judaism, Christianity, and Islam) emphasize human uniqueness as compared to Eastern philosophies and religions (e.g., Buddhism, neo-Confucianism, Taoism, Shinto, Japanese adaptation of biological materialism).