The uncanny valley is a hypothesis regarding the field of robotics and computer graphic animation. The theory 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.
A number of theories have been proposed to explain the cognitive mechanism underlying the phenomenon. As appearance and motion become less distinguishable from a human being, 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 is activated.
In addition, the viewing of a not quite real human animation or robot elicits an innate fear of death, pathogen avoidance, and the irrational belief that aging and death as a central premise of life apply to all others but oneself. The jerkiness of an android’s movements could be unsettling because it elicits a fear of losing bodily control.
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 concept of the uncanny valley is taken seriously by the film industry due to negative audience reactions to CGI animations. The 2004 CGI animated film The Polar Express was criticized by reviewers who felt that the appearance and movements of the characters were creepy or eerie.