Uncanny valley

The uncanny valley is a hypothesis 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, simply entitled "The Uncanny" ("Das Unheimliche"). A similar problem exists in realistic 3D computer animation, such as with the film The Polar Express and Beowulf.


Mori's hypothesis states that as a robot is made more humanlike in its appearance and motion, the emotional response from a human being to the robot will become increasingly positive and empathic, until a point is reached beyond which the response quickly becomes that of strong repulsion. However, as the appearance and motion continue to become less distinguishable from a human being, the emotional response becomes positive once more and approaches human-to-human empathy levels.

This area of repulsive response aroused by a robot with appearance and motion between a "barely-human" and "fully human" entity is called the uncanny valley. The name captures the idea that a robot which is "almost human" will seem overly "strange" to a human being and thus will fail to evoke the empathetic response required for productive human-robot interaction.

Theoretical basis

The phenomenon can be explained by the notion that, if an entity is sufficiently non-humanlike, then the humanlike characteristics will tend to stand out and be noticed easily, generating empathy. On the other hand, if the entity is "almost human", then the non-human characteristics will be the ones that stand out, leading to a feeling of "strangeness" in the human viewer. In other words, a robot stuck inside the uncanny valley is no longer being judged by the standards of a robot doing a good 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.

Another possibility is that seriously ill individuals and corpses exhibit many visual anomalies similar to the ones seen in humanoid robots and so elicit the same alarm and revulsion. The reaction may become worse with robots since there is no overt reason for it to occur, whereas distaste for the sight of a corpse is a feeling easy to understand.

It is sometimes regarded as possible that the "uncanny valley" effect evolved as a means of instinctively identifying and ostracizing humans that might prove (specifically in terms of breeding and long-term care) detrimental to the group.


According to writer Jamais Cascio, a similar "uncanny valley" effect could show up when humans begin modifying themselves with transhuman enhancements (cf. body modification), which aim to improve the abilities of the human body beyond what would normally be possible, be it eyesight, muscle strength, or cognition. So long as these enhancements remain within a perceived norm of human behavior, a negative reaction is unlikely, but once individuals supplant normal human variety, revulsion can be expected. However, according to this theory, once such technologies gain further distance from human norms, "transhuman" individuals would cease to be judged on human levels and instead be regarded as separate entities altogether (this point is what has been dubbed "posthuman"), and it is here that acceptance would rise once again out of the uncanny valley.


Some roboticists have heavily criticized the theory, arguing that Mori had no basis for the rightmost part of his chart, as human-like robots have only recently become technically possible. David Hanson, a roboticist who developed a realistic robotic copy of his girlfriend's head, said that the idea of the uncanny valley is "really pseudoscientific, but people treat it like it is science. Sara Kiesler, a human-robot interaction researcher at Carnegie Mellon University, questioned uncanny valley's scientific status, stating, "We have evidence that it's true, and evidence that it's not. Roboticist Dario Floreano stated that uncanny valley is not based on scientific evidence, but is taken seriously by the film industry due to negative audience reactions to the animated baby in Pixar's 1988 short film Tin Toy. Christoph Bartneck pointed out that the cultural background of the users might have a considerable influence on how androids are being perceived, including their perception of the uncanny valley.

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