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.
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
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.
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.
- Mori, Masahiro (1970). Bukimi no tani The uncanny valley (K. F. MacDorman & T. Minato, Trans.). Energy, 7(4), 33–35. (Originally 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.
- Bartneck, C., Kanda, T., Ishiguro, H., & Hagita, N. (2007). Is the Uncanny Valley an Uncanny Cliff? Proceedings of the 16th IEEE, RO-MAN 2007, Jeju, Korea, pp. 368-373. DOI: 10.1109/ROMAN.2007.4415111 html
- 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.)
- MacDorman, Karl F. & Ishiguro, H. (2006). The uncanny advantage of using androids in cognitive science research. Interaction Studies, 7(3), 297-337.
- MacDorman, K. F. (2006). Subjective ratings of robot video clips for human likeness, familiarity, and eeriness: An exploration of the uncanny valley. ICCS/CogSci-2006 Long Symposium: Toward Social Mechanisms of Android Science. July 26 2006. Vancouver, Canada.
- Ho, C.-C., MacDorman, K. F., & Pramono, Z. A. D. (2008). Human emotion and the uncanny valley: A GLM, MDS, and ISOMAP analysis of robot video ratings. Proceedings of the Third ACM/IEEE International Conference on Human-Robot Interaction. March 11-14. Amsterdam.
- Green, R. D., MacDorman, K. F., Ho, C.-C., & Vasudevan, S. K. (2008). Sensitivity to the proportions of faces that vary in human likeness Computers in Human Behavior
- H. Ishiguro (2005). Android science: Toward a new cross-disciplinary framework CogSci-2005 Workshop: Toward Social Mechanisms of Android Science, 2005, pp. 1–6.
- Carpenter, J., Eliot, M. & Schultheis, D. (2006). The Uncanny Valley: Making human-nonhuman distinctions Proceedings of the 5th International Conference on Cognitive Science, 81-82.Vancouver, B.C., Canada.
- Carpenter, J., Eliot, M. & Schultheis, D. (2006). Machine or friend: understanding users’ preferences for and expectations of a humanoid robot companion Proceedings of 5th conference on Design and Emotion, CD-ROM. Gothenburg, Sweden.
- IEEE-RAS Humanoids-2005 Workshop: Views on the Uncanny Valley Was held in Tsukuba, Japan, near Tokyo on December 5 2005.
- The Uncanny Valley (Dave Bryant)
- Almost too human and lifelike for comfort - research journal for an uncanny valley PhD project
- Relation between motion and appearance is communication between androids and humans
- Android Science video, the Discovery Channel, 24 March 2005, discusses android science, the uncanny valley and features an Actroid.
- Wired article: "Why is this man smiling?", June 2002.
- The Polar Express: A Virtual Train Wreck, Part 1 - Animation Director Ward Jenkins discusses in length about the use of motion capture in the film. In Part 2, he tries to "fix" the uncanny valley problem by using Photoshop to tweak some of the characters in the film.