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 1970. The principle 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 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.
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.
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.
Another possibility is that infected individuals and corpses exhibit many visual anomalies similar to the ones seen with 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 an easy feeling to understand. Behavioural anomalies are also indicative of illness, neurological conditions or mental dysfunction and again evoke acutely negative emotions.
Some roboticists have heavily criticized the theory, arguing that Mori had no basis for the rightmost 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 is 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.
One counterpoint to the denial of the existence of the Valley in films is the early Pixar production Tin Toy. There, the baby shown is fully computer generated yet looks less than human and can prove frightening or unpleasant to children. The effect is lessened by the two dimensional nature of the character, but the overly defined wrinkles and (comparatively) primitive rendering of the spittle makes the character appear evil or otherwordly. A similar effect is seen in the doll’s head character in the film Toy Story. The character can be again frightening to children because it is in essence a mobile deformed human head. Even if it is not frightening, most children prefer the cute appeal of the aliens or indeed Woody because there is less human resemblence.
In 2001, Square Pictures‘ photorealistic movie, Final Fantasy: The Spirits Within failed at the box-office and is often cited as a possible victim of the Uncanny Valley. The movie was the first major wide-released CGI film to feature photorealistic characters, and in turn brought about quite a bit of attention from movie critics and filmmakers alike. The Uncanny Valley theory is thought to be most prominent in Final Fantasy’s character movements. The characters also lack any visible perspiration, as well as eye and lip movements that seem “off” – probably two of the most difficult techniques to accomplish in computer animation.
It has been said the best way to accomplish convincing human movements and to “jump” the Uncanny Valley in computer animation is to combine both motion capture and keyframing techniques. Though the former has become a popular technique, keyframing is still widely used throughout the animation industry. The film adaptation of J.R.R. Tolkien‘s The Lord of the Rings, which features the character Gollum, uses this combined technique with stunning results. Note, however, that Gollum’s eyes and face were animated using only keyframing. Note also that the Gollum animation also featured advances in modelling (including skin texture, and effects such as saliva around lips) which allow the character’s external appearance to reach the other side of the Valley. One obvious caveat with Gollum, however, is that the character is evidently non-human (and indeed intentionally uncanny to start with) and so may not trigger the same response as a human figure would when modelled using the same techniques.
Despite advances in computer animation, some feel the Uncanny Valley affected two CGI films of 2004, The Incredibles and The Polar Express. The close dates of release led to many critics’ comparison of the two movies, with some preferring the deliberately stylized appearance of the characters in The Incredibles over the more human-like characters in The Polar Express (which were described by many critics as being “disturbing”). Pixar stated that the reason for stylizing the characters in the “Incredibles” was not due to an inability to make the characters more realisitic, but an attempt to avoid the Uncanny Valley.
The CG animation Final Flight of the Osiris in the Animatrix also suffers from this – although, as this was also made with the same techniques as in Final Fantasy: The Spirits Within, it was in some ways expected to. Erotic sequences with Uncanny Valley characters, as featured in Final Flight, are particularly disturbing, since they provide conflicting messages of “this is arousing” and “this is non-human”.
The Uncanny Valley is also a plot point in some movies about robotics. A.I.: Artificial Intelligence centers on a future where many people are disturbed at how realistic the new line of androids is. For example, a rowdy crowd that rejoices in watching robot destruction derbies called “Flesh Fairs” falls silent when the next subject about to be ripped apart appears to be an adorable human boy. In I, Robot, the newest wave of U.S. Robotics robots is far more humanoid in facial expressions and appearance. This disturbs main character Det. Del Spooner, who was already bothered by the boxy metal robots that preceded them. “Why do you give them faces?” he asks one of the robots’ programmers as he stares into a sea of identical new robots. He then discharges his firearm into the “face” of a robot at point-blank range, effectively making his point to the movie audience who will gasp at the sight of him “executing” a “person.”
Uncanny Valley as an analogy outside AI
In ESPN‘s “Page 2” feature , columnist Patrick Hruby explained Uncanny Valley in the traditional sense, noting that in Madden NFL 06 the players exhibit the unnervingly almost-human features that plague many CGI films. The column extended the Uncanny Valley term to the well-documented analogous debate over what sort of sports fan suffers more, one who roots for a perennial loser or one who roots for a perennial second-best. Hruby suggests that the perennial second-best fans, like the Red Sox Nation, suffer more because of the “Uncanny Valley” between the team’s clear potential for perfection and their history of falling just short of the championship.
External links and references
- Mori, Masahiro (1970). Bukimi no tani the uncanny valley. Energy, 7, 33–35. (In Japanese)
- Mori, Masahiro (2005). On the Uncanny Valley. Proceedings of the Humanoids-2005 workshop: Views of the Uncanny Valley. 5 December 2005, Tsukuba, Japan.
- MacDorman, Karl F. (2005). Androids as an experimental apparatus: Why is there an uncanny valley and can we exploit it? CogSci-2005 Workshop: Toward Social Mechanisms of Android Science, 106-118. (An English translation of Mori’s “The Uncanny Valley” made by Karl MacDorman and Takashi Minato appears in Appendix B of the paper.)
- IEEE-RAS Humanoids-2005 Workshop: Views on the Uncanny Valley. Was held in Tsukuba, Japan, near Tokyo on December 5, 2005.
- 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)
- Almost too human and lifelike for comfort – the (ongoing) journal of an uncanny valley MSc research project
-  (Relation between motion and appearance is communication between androids and humans)
-  (Discovery Channel video excerpt “Android Science” March 2005)
-  (Wired article: “Why is this man smiling?”, June 2002