Uncanny valley

Mate selection: Automatic, stimulus-driven appraisals of uncanny stimuli elicit aversion by activating an evolved 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 that are predictive of those traits.^[8]

cognitive

: Viewing an "uncanny" robot elicits an innate fear of death and culturally supported defenses for coping with death's inevitability.... [P]artially disassembled androids...play on subconscious fears of reduction, replacement, and annihilation: (1) A mechanism with a human façade and a mechanical interior plays on our subconscious fear that we are all just soulless machines. (2) Androids in various states of mutilation, decapitation, or disassembly are reminiscent of a battlefield after a conflict and, as such, serve as a reminder of our mortality. (3) Since most androids are copies of actual people, they are doppelgängers and may elicit a fear of being replaced, on the job, in a relationship, and so on. (4) The jerkiness of an android's movements could be unsettling because it elicits a fear of losing bodily control.^[9]

Mortality salience

avoidance: Uncanny stimuli may activate a cognitive mechanism that originally evolved to motivate the avoidance of potential sources of pathogens by eliciting a disgust response. "The more human an organism looks, the stronger the aversion to its defects, because (1) defects indicate disease, (2) more human-looking organisms are more closely related to human beings genetically, and (3) the probability of contracting disease-causing bacteria, viruses, and other parasites increases with genetic similarity."^[8] The visual anomalies of androids, robots, and other animated human characters cause reactions of alarm and revulsion, similar to corpses and visibly diseased individuals.^[10][11]

Pathogen

: Stimuli with human and nonhuman traits undermine our sense of human identity by linking qualitatively different categories, human and nonhuman, by a quantitative metric: degree of human likeness.^[12]

Sorites paradoxes

Violation of human norms: If an entity looks sufficiently nonhuman, its human characteristics are noticeable, generating empathy. However, if the entity looks almost human, it elicits our model of a human other and its detailed normative expectations. The nonhuman characteristics are noticeable, giving the human viewer a sense of strangeness. In other words, a robot which has an appearance in the uncanny valley range is not judged as a robot doing a passable job at pretending to be human, but instead as an abnormal human doing a bad job at seeming like a normal person. This has been associated with perceptual uncertainty and the theory of predictive coding.^[14][15]

[13]

Conflicting perceptual cues: The negative effect associated with uncanny stimuli is produced by the activation of conflicting cognitive representations. Perceptual tension occurs when an individual perceives conflicting cues to membership, such as when a humanoid figure moves like a robot, or has other visible robot features. This cognitive conflict is experienced as psychological discomfort (i.e., "eeriness"), much like the discomfort that is experienced with cognitive dissonance.^[16][17] Several studies support this possibility. Mathur and Reichling found that the time subjects took to gauge a robot face's human- or mechanical-resemblance peaked for faces deepest in the uncanny valley, suggesting that perceptually classifying these faces as "human" or "robot" posed a greater cognitive challenge.^[18] However, they found that while perceptual confusion coincided with the uncanny valley, it did not mediate the effect of the uncanny valley on subjects' social and emotional reactions—suggesting that perceptual confusion may not be the mechanism behind the uncanny valley effect. Burleigh and colleagues demonstrated that faces at the midpoint between human and non-human stimuli produced a level of reported eeriness that diverged from an otherwise linear model relating human-likeness to affect.^[19] Yamada et al. found that cognitive difficulty was associated with negative affect at the midpoint of a morphed continuum (e.g., a series of stimuli morphing between a cartoon dog and a real dog).^[20] Ferrey et al. demonstrated that the midpoint between images on a continuum anchored by two stimulus categories produced a maximum of negative affect, and found this with both human and non-human entities.^[16] Schoenherr and Burleigh provide examples from history and culture that evidence an aversion to hybrid entities, such as the aversion to genetically modified organisms ("Frankenfoods").^[21] Finally, Moore developed a Bayesian mathematical model that provides a quantitative account of perceptual conflict.^[22] There has been some debate as to the precise mechanisms that are responsible. It has been argued that the effect is driven by categorization difficulty,^[19][20] configural processing, perceptual mismatch,^[23] frequency-based sensitization,^[24] and inhibitory devaluation.^[16]

category

Threat to humans' distinctiveness and identity: Negative reactions toward very humanlike robots can be related to the challenge that this kind of robot leads to the categorical human – non-human distinction. Kaplan stated that these new machines challenge human uniqueness, pushing for a redefinition of humanness. Ferrari, Paladino and Jetten^[26] found that the increase of anthropomorphic appearance of a robot leads to an enhancement of threat to the human distinctiveness and identity. The more a robot resembles a real person, the more it represents a challenge to our social identity as human beings.

[25]

Religious definition of human identity: The existence of artificial but humanlike entities is viewed by some as a threat to the concept of human identity. An example can be found in the theoretical framework of psychiatrist . Yalom explains that humans construct psychological defenses to avoid existential anxiety stemming from death. One of these defenses is 'specialness', the irrational belief that aging and death as central premises of life apply to all others but oneself.^[27] The experience of the very humanlike "living" robot can be so rich and compelling that it challenges humans' notions of "specialness" and existential defenses, eliciting existential anxiety. In folklore, the creation of human-like, but soulless, beings is often shown to be unwise, as with the golem in Judaism, whose absence of human empathy and spirit can lead to disaster, however good the intentions of its creator.^[28]

Irvin Yalom

Uncanny valley of the mind or AI: Due to rapid advancements in the areas of and affective computing, cognitive scientists have also suggested the possibility of an "uncanny valley of mind".^[29][30] Accordingly, people might experience strong feelings of aversion if they encounter highly advanced, emotion-sensitive technology. Among the possible explanations for this phenomenon, both a perceived loss of human uniqueness and expectations of immediate physical harm are discussed by contemporary research.

artificial intelligence

Design elements should match in human realism. A robot may look uncanny when human and nonhuman elements are mixed. For example, both a robot with a synthetic voice or a human being with a human voice have been found to be less eerie than a robot with a human voice or a human being with a synthetic voice. For a robot to give a more positive impression, its degree of human realism in appearance should also match its degree of human realism in behavior.^[43] If an animated character looks more human than its movement, this gives a negative impression.^[44] Human neuroimaging studies also indicate matching appearance and motion kinematics are important.^[13][45][46]

[42]

Reducing conflict and uncertainty by matching appearance, behavior, and ability. In terms of performance, if a robot looks too appliance-like, people expect little from it; if it looks too human, people expect too much from it. A highly human-like appearance leads to an expectation that certain behaviors are present, such as humanlike motion dynamics. This likely operates at a sub-conscious level and may have a biological basis. Neuroscientists have noted "when the brain's expectations are not met, the brain...generates a 'prediction error'. As human-like artificial agents become more commonplace, perhaps our perceptual systems will be re-tuned to accommodate these new social partners. Or perhaps, we will decide 'it is not a good idea to make [robots] so clearly in our image after all'."^[13][46][47]

[43]

Human facial proportions and photorealistic texture should only be used together. A photorealistic human texture demands human facial proportions, or the computer generated character can result in the uncanny valley. Abnormal facial proportions, including those typically used by artists to enhance attractiveness (e.g., larger eyes), can look eerie with a photorealistic human texture.

The uncanny valley effect is a group of phenomena. Phenomena considered as exhibiting the uncanny valley effect can be diverse, involve different sense modalities, and have multiple, possibly overlapping causes. People's cultural heritage may have a considerable influence on how androids are perceived with respect to the uncanny valley.^[48]

heterogeneous

The uncanny valley effect may be generational. Younger generations, more used to (CGI), robots, and such, may be less likely to be affected by this hypothesized issue.^[49]

computer-generated imagery

The uncanny valley effect is simply a specific case of such as categorization and frequency-based effects. In contrast to the assumption that the uncanny valley is based on a heterogeneous group of phenomena, recent arguments have suggested that uncanny valley-like phenomena simply represent the products of information processing such as categorization. Cheetham et al.^[50] have argued that the uncanny valley effect can be understood in terms of categorization processes, with a category boundary defining 'the valley'. Extending this argument, Burleigh and Schoenherr^[51] suggested that the effects associated with the uncanny valley can be divided into those attributable to the category boundary and individual exemplar frequency. Namely, the negative affective responses attributed to the uncanny valley were simply a result of the frequency of exposure, similar to the mere-exposure effect. By varying the frequency of training items, they were able to demonstrate a dissociation between cognitive uncertainty based on the category boundary and affective uncertainty based on the frequency of training exemplars. In a follow-up study, Schoenherr and Burleigh^[52] demonstrated that an instructional manipulation affected categorization accuracy but not ratings of negative affect. Thus, generational effects and cultural artifacts can be accounted for with basic information processing mechanisms.^[21] These and related findings have been used to argue that the uncanny valley is merely an artifact of having greater familiarity with members of human categories and does not reflect a unique phenomenon.

information processing

The uncanny valley effect occurs at any degree of human likeness. Hanson has also stated that uncanny entities may appear anywhere in a spectrum ranging from the abstract (e.g., 's robot Lazlo) to the perfectly human (e.g., cosmetically atypical people).^[53] Capgras delusion is a relatively rare condition in which the patient believes that people (or, in some cases, things) have been replaced with duplicates. These duplicates are accepted rationally as identical in physical properties, but the irrational belief is held that the "true" entity has been replaced with something else. Some people with Capgras delusion claim that the duplicate is a robot. Ellis and Lewis argue that the delusion arises from an intact system for overt recognition coupled with a damaged system for covert recognition, which results in conflict over an individual being identifiable but not familiar in any emotional sense.^[54] This supports the opinion that the uncanny valley effect could occur due to issues of categorical perception that are particular to how the brain processes information.^[46][55]

MIT

Good design can avoid the uncanny valley effect. has criticized Mori's hypothesis that entities having an almost human appearance will necessarily be evaluated negatively.^[53] He has shown that the uncanny valley effect could be eliminated by adding neotenous, cartoonish features to entities that had formerly caused an uncanny valley effect.^[53] This method incorporates the idea that humans find characteristics appealing when they are reminiscent of the young of our own (as well as many other) species, as used in cartoons.

David Hanson

According to roboticist , the baby character Billy in Pixar's groundbreaking 1988 animated short movie Tin Toy provoked negative audience reactions, which first caused the movie industry to consider the concept of the uncanny valley seriously.^[59][60]

Dario Floreano

The 2001 movie , one of the first photorealistic computer-animated feature movies, provoked negative reactions from some viewers due to its near-realistic yet imperfect visual depictions of human characters.^[61][62][63] The Guardian critic Peter Bradshaw stated that while the movie's animation is brilliant, the "solemnly realist human faces look shriekingly phoney precisely because they're almost there but not quite".^[64] Rolling Stone critic Peter Travers wrote of the movie, "At first it's fun to watch the characters, [...] But then you notice a coldness in the eyes, a mechanical quality in the movements".^[65]

Final Fantasy: The Spirits Within

Several reviewers of the 2004 animated movie termed its animation eerie. CNN.com reviewer Paul Clinton wrote, "Those human characters in the film come across as downright... well, creepy. So The Polar Express is at best disconcerting, and at worst, a wee bit horrifying".^[66] The term "eerie" was used by reviewers Kurt Loder^[67] and Manohla Dargis,^[68] among others. Newsday reviewer John Anderson called the movie's characters "creepy" and "dead-eyed", and wrote that "The Polar Express is a zombie train".^[69] Animation director Ward Jenkins wrote an online analysis describing how changes to the Polar Express characters' appearance, especially to their eyes and eyebrows, could have avoided what he considered a feeling of deadness in their faces.^[70]

The Polar Express

In a review of the 2007 animated movie , New York Times technology writer David Gallagher wrote that the movie failed the uncanny valley test, stating that the movie's villain, the monster Grendel, was "only slightly scarier" than the "closeups of our hero Beowulf's face... allowing viewers to admire every hair in his 3-D digital stubble".^[71]

Beowulf

Some reviewers of the 2009 animated film criticized its animation as creepy. Joe Neumaier of the New York Daily News said of the movie, "The motion-capture does no favors to co-stars [Gary] Oldman, Colin Firth and Robin Wright Penn, since, as in 'Polar Express,' the animated eyes never seem to focus. And for all the photorealism, when characters get wiggly-limbed and bouncy as in standard Disney cartoons, it's off-putting".^[72] Mary Elizabeth Williams of Salon.com wrote of the film, "In the center of the action is Jim Carrey -- or at least a dead-eyed, doll-like version of Carrey".^[73]

A Christmas Carol

The 2011 animated movie was widely criticized for being creepy and unnatural because of its style of animation. The movie was among the biggest box office bombs in history, which may have been due in part to audience revulsion.^{[74][75][76][77]} (Mars Needs Moms was produced by Robert Zemeckis's production company, ImageMovers, which had previously produced The Polar Express, Beowulf, and A Christmas Carol.)

Mars Needs Moms

Reviewers had mixed opinions regarding whether the 2011 animated movie was affected by the uncanny valley effect. Daniel D. Snyder of The Atlantic wrote, "Instead of trying to bring to life Herge's beautiful artwork, Spielberg and co. have opted to bring the movie into the 3D era using trendy motion-capture technique to recreate Tintin and his friends. Tintin's original face, while barebones, never suffered for a lack of expression. It's now outfitted with an alien and unfamiliar visage, his plastic skin dotted with pores and subtle wrinkles." He added, "In bringing them to life, Spielberg has made the characters dead.".^[78] N.B. of The Economist termed elements of the animation "grotesque", writing, "Tintin, Captain Haddock and the others exist in settings that are almost photo-realistic, and nearly all of their features are those of flesh-and-blood people. And yet they still have the sausage fingers and distended noses of comic-strip characters. It's not so much 'The Secret of the Unicorn' as 'The Invasion of the Body Snatchers'".^[79] However, other reviewers felt that the movie avoided the uncanny valley effect despite its animated characters' realism. Critic Dana Stevens of Slate wrote, "With the possible exception of the title character, the animated cast of Tintin narrowly escapes entrapment in the so-called 'uncanny valley'".^[80] Wired magazine editor Kevin Kelly wrote of the movie, "we have passed beyond the uncanny valley into the plains of hyperreality".^[81]

The Adventures of Tintin: The Secret of the Unicorn

In 2014, the titular protagonist of the movie got a redesign which was described by some as "creepy".^[82]

Bob the Builder

In the French movie it uses motion capture, the apes were criticized for looking creepy. As this review points out, they have "weirdly humanoid figures" and "recognisably human faces".^[83]

Animal Kingdom: Let's Go Ape

The 2019 film , a remake of the 1994 film that featured photo-realistic digital animals instead of the earlier movie's more traditional animation, divided critics about the effectiveness of its imagery. Ann Hornaday of The Washington Post wrote that the images were so realistic that "2019 might best be remembered as the summer we left the Uncanny Valley for good".^[84] However, other critics felt that the realism of the animals and setting rendered the scenes where the characters sing and dance disturbing and "weird".^[85][86]

The Lion King

The 2020 movie was delayed for three months to make the title character's appearance less human-like and more cartoonish, after an extremely negative audience reaction to the movie's first trailer.^[87]

Sonic the Hedgehog

Multiple commentators cited the CGI half-human half-cat characters in the 2019 movie as an example of the uncanny valley effect, first after the release of the trailer for the movie^[88][89][90] and then after the movie's actual release.^[91]

Cats

In the 2022 Disney animated movie , the uncanny valley is mentioned when the animated duo visits a place where several realistic CGI characters, including a Cats cameo from the 2019 movie, are inhabitants.^[92]

Chip 'n Dale: Rescue Rangers

In the 2022 series She-Hulk: Attorney at Law, the appearance of the main character, She-Hulk, who is depicted via CGI, was criticized by some reviewers as suffering from the uncanny valley effect, and negatively compared to the appearance of the Hulk in the same series.^[93][94][95]

Disney+

Miklósi, Ádám and Korondi, Péter and Matellán, Vicente and Gácsi, Márta. . Frontiers in Psychology, 2017, 8, p. 958

"Ethorobotics: A New Approach to Human-Robot Relationship"

UCSD news release about human brain and the uncanny valley.

Your Brain on Androids