The Uncanny Valley is a principle of robotics concerning the emotional response of humans to robots and other non-human entities. It was theorized by Japanese roboticist Masahiro Mori in the late 1970s through psychological experiments in which he measured human response to robots of varying degrees of anthropomorphism. The principle states that as a robot is made more humanlike in its appearance and motion the emotional response from a human being to robot will become increasingly positive and empathic, until a point is reached at which the response suddenly becomes strongly repulsive; as the appearance and motion are made to be indistinguishable to that of human being, the emotional response becomes positive once more and approaches human-human empathy levels.

Emotional response of human subjects is plotted against anthropomorphism of a robot, following Mori's results. The Uncanny Valley is the region of negative emotional response for robots that seems "almost human".

This gap 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 harkens to the notion that a robot which is "almost human" will seem overly "strange" to a human being and thus will fail to evoke the requisite empathetic response required for productive human-robot interaction. Mori separately tested responses to variations in the movement and appearance of the robot from completely machinely to almost human. For both variables, the chart displayed a similar curve as depicted in the illustration.

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.

Some roboticists have heavily criticized the theory, arguing that Mori had no basis for the right part of his chart, as human-like robots are only now technically possible (and still only partially). David Hanson, a roboticist who developed a realistic robotic copy of his girlfriend's head, said the idea of the Uncanny Valley was "really pseudoscientific, but people treat it like it's science." Sara Kiesler , a human-robot interaction researcher at Carnegie Mellon University, questioned Uncanny Valley's scientific status, noting that "we have evidence that it’s true, and evidence that it’s not."

The Uncanny Valley in film

Although originally resulting from experimental data and applied only to robotics, the principle has been applied to computer animation characters. American film critic Roger Ebert has applied the notion of Uncanny Valley to the use of make-up and costumes of humanoid creatures in movies.

The Uncanny Valley was considered by some to be the reason behind the difficulty in creating computer-animated characters. Critics of computer animated films sometimes invoke the Uncanny Valley when explaining their dislike for a particular film. The principle leads to the conclusion that to generate a positive emotional response in human beings, it is often better to include fewer human characteristics in the entity, lest it fall into the Uncanny Valley. Critics argue, however, that there has been no evidence in animation or filmmaking for the existence of the Uncanny Valley, even though movie effects have gradually developed to the point when humans are digitally rendered realistically and without evoking negative emotions from the viewers. Proponents of this view argue that nowhere between 1970s and 2000s have moviemakers actually faced the challenge of the Valley.

An example of the Uncanny Valley was seen in late 2004, with the close release of two CG-animated films, The Incredibles and The Polar Express. Many critics preferred the deliberately stylised appearance of the characters in The Incredibles to the human-like characters in The Polar Express (which were described by many critics as being "disturbing").

External links and references

• Masahiro Mori: The Buddha in the Robot (Charles E. Tuttle Co., 1982; ISBN 4333010020)
• The Man Who Mistook His Girlfriend For A Robot (Dan Ferber, Popular Science, September 2003)
• The Uncanny Valley (Dave Bryant)
• Pixar and the Uncanny Valley (RobotJohnny.com, 4 October 2004)