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Cited by 500Social Robot Interaction and HRIVirtual Reality Applications and ImpactsFace Recognition and Perception

A review of empirical evidence on different uncanny valley hypotheses: support for perceptual mismatch as one road to the valley of eeriness

Open access
Kätsyri, Jari, Förger, Klaus, Mäkäräinen, Meeri, Takala, Tapio·2015·Frontiers in Psychology
DOI 10.3389/fpsyg.2015.00390PMC PMC4392592
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Abstract

The uncanny valley hypothesis, proposed already in the 1970s, suggests that almost but not fully humanlike artificial characters will trigger a profound sense of unease. This hypothesis has become widely acknowledged both in the popular media and scientific research. Surprisingly, empirical evidence for the hypothesis has remained inconsistent. In the present article, we reinterpret the original uncanny valley hypothesis and review empirical evidence for different theoretically motivated uncanny valley hypotheses. The uncanny valley could be understood as the naïve claim that any kind of human-likeness manipulation will lead to experienced negative affinity at close-to-realistic levels. More recent hypotheses have suggested that the uncanny valley would be caused by artificial-human categorization difficulty or by a perceptual mismatch between artificial and human features. Original formulation also suggested that movement would modulate the uncanny valley. The reviewed empirical literature failed to provide consistent support for the naïve uncanny valley hypothesis or the modulatory effects of movement. Results on the categorization difficulty hypothesis were still too scarce to allow drawing firm conclusions. In contrast, good support was found for the perceptual mismatch hypothesis. Taken together, the present review findings suggest that the uncanny valley exists only under specific conditions. More research is still needed to pinpoint the exact conditions under which the uncanny valley phenomenon manifests itself.

AI snapshot

Written from the paper’s full text.

TL;DR

This systematic review reinterprets Mori’s uncanny valley hypothesis as several testable hypotheses and reviews empirical evidence for each. It finds little support for the naïve claim that any human-likeness manipulation produces the uncanny valley, but good support for perceptual mismatch explanations, especially inconsistent realism and atypical features on humanlike characters.

Key findings

  • The naïve uncanny valley proper (H1a) received almost no support: 1 of 8 studies supported it, while the general linear human-likeness prediction (H1b) was supported in 7 of 9 studies.
  • Movement hypotheses were not supported: H2a had 0 of 2 studies in favor, H2b had 2 of 2, and no studies addressing movement modulation (H2c) survived selection.
  • Categorization ambiguity evidence was mixed: categorical perception of morphed human-likeness continua was supported (H3a 4/4; H3b 3/3), but negative affinity at the category boundary was not (H3c 0/2; H3d 0/3; H3e 0/1).
  • Perceptual mismatch hypotheses received good support: inconsistent human-likeness (H4a) was supported in 4 of 4 studies, and atypicality (H4b) in 3 of 4 studies.

Methods

  • Systematic review of empirical uncanny valley studies. Searches in Scopus (N = 273), PubMed (N = 23), Science Direct (N = 134), and Web of Science (N = 114), augmented by 6 other articles, yielded an initial list of N = 550; after screening N = 125, the final selected list was N = 17 articles.
  • Studies were evaluated against inclusion criteria and validity threats adapted from Shadish et al. (2002), covering statistical conclusion, internal, construct, and external validity.
  • Because studies were heterogeneous and most did not report effect sizes, the authors used a “box score” count of significant and non-significant findings rather than quantitative meta-analysis, with a 30% threshold for considering positive findings supportive.

Limitations

  • The authors state that their conceptual analysis relied on the English translation and secondary sources rather than Mori’s original Japanese article.
  • The review included only studies using self-report affinity measures, omitting physiological and behavioral studies such as gaze tracking and haemodynamic response measurements; the authors also note that heterogeneous self-report items reduced comparability across studies.
  • The authors state that their evaluation criteria are open to subjective interpretation, do not cover all aspects of experimental validity, and should not be taken as evidence for the validity of the evaluated studies themselves; they also note that only categorization ambiguity and perceptual mismatch explanations were reviewed, leaving other explanations aside.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.3389/fpsyg.2015.00390

Cites

73 of 73 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 73 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    Results on the categorization difficulty hypothesis were too scarce to allow drawing firm conclusions.

    “Results on the categorization difficulty hypothesis were still too scarce to allow drawing firm conclusions.”
    Quote in the paperSubstantial claim
  • Findingnone given

    Empirical evidence for the uncanny valley hypothesis has remained inconsistent.

    “Surprisingly, empirical evidence for the hypothesis has remained inconsistent.”
    • Also stated in: § Introduction · hedged
      “Against this background, it is surprising that empirical evidence for the uncanny valley hypothesis is still ambiguous if not non-existent.”
    Quote in the paperSubstantial claim
  • Findingown data

    Good support was found for the perceptual mismatch hypothesis.

    “In contrast, good support was found for the perceptual mismatch hypothesis.”
    Quote in the paperSubstantial claim
  • Findingown data

    The reviewed empirical literature failed to provide consistent support for the naïve uncanny valley hypothesis.

    “The reviewed empirical literature failed to provide consistent support for the naïve uncanny valley hypothesis or the modulatory effects of movement.”
    Quote in the paperSubstantial claim
  • Findingown data

    The reviewed empirical literature failed to provide consistent support for the modulatory effects of movement.

    “The reviewed empirical literature failed to provide consistent support for the naïve uncanny valley hypothesis or the modulatory effects of movement.”
    Quote in the paperSubstantial claim
  • Classified as probably not a substantial claim. 45
  • May combine two claims. 17

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingcitation

    Previous uncanny valley studies have employed at least 11 evenly distributed human-likeness steps along the human-likeness continuum.

    “In practice, previous uncanny valley studies have employed at least 11 evenly distributed human-likeness steps along the human-likeness continuum (e.g., Looser and Wheatley, 2010; Cheetham et al., 2011, 2014).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Looser and Wheatley, 2010

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    • cites Cheetham et al., 2011 source

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    • cites Cheetham et al., 2014 source

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    Findingcitation

    The Ho and MacDorman (2010) scale has already been applied in at least two studies.

    “The scale has already been applied in at least two studies (Mitchell et al., 2011; MacDorman et al., 2013).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Mitchell et al., 2011 source

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    • cites MacDorman et al., 2013 source

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  • May combine two claims.

    Findingcitation

    The two studies on modulatory movement effects provided conflicting evidence: one reported a significant increase and the other a significant decrease in negative affinity for moving characters.

    “Furthermore, these studies provided conflicting evidence: the former reported a significant increase and the latter a significant decrease in negative affinity for the moving characters.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites McDonnell et al., 2012 source

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    • cites Piwek et al., 2014 source

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    Findingcitation

    Two studies demonstrated modulatory movement effects, but these effects were specific to plausible outlier characters (ill-looking face in McDonnell et al., 2012; zombie character in Piwek et al., 2014).

    “Two studies demonstrated modulatory movement effects; however, these effects were specific to plausible outlier characters (ill-looking face in McDonnell et al., 2012; and zombie character in Piwek et al., 2014).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites McDonnell et al., 2012 source

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    • cites Piwek et al., 2014 source

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  • May combine two claims.

    Findingown data

    Only two studies tested affinity responses elicited by categorization ambiguity (H3c), and neither could be taken as evidence in favor of this hypothesis.

    “In contrast, we managed to identify only two studies that tested affinity responses elicited by categorization ambiguity (H3c); neither of which could be taken as evidence in favor of this hypothesis.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Findingnone given

    Refined uncanny valley hypotheses have up to date been studied using only static stimuli.

    “refined uncanny valley hypotheses (see below) have up to date been studied using only static stimuli”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingcitation

    In Yamada et al. (2013), two participants reported spontaneously after the experiment that they evaluated the likability of the images based on the presence or absence of morphing noise.

    “Consistently, two participants in this study had reported spontaneously after the experiment that “they [had] evaluated the likability of the images based on the presence or absence of morphing noise” (ibid., 4).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Yamada et al., 2013 source

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  • May combine two claims.

    Findingcitation

    Burleigh et al. (2013) failed to demonstrate higher eeriness or unpleasantness for increasingly realistic faces, contrary to H4b.

    “Contrary to H4b, one other study (Burleigh et al., 2013) failed to demonstrate higher eeriness or unpleasantness for increasingly realistic faces.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Burleigh et al., 2013 source

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  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing), S4 (based). May combine two claims.

    Interpretationreasoning

    The location of the category boundary cannot be known in advance, so the minimum number of required stimulus levels for testing the category identification hypothesis cannot be determined precisely.

    “Given that the location of category boundary cannot be known in advance, the minimum number of required stimulus levels for testing this hypothesis cannot be determined precisely.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    The suggestion that negative affinity is caused by ambiguity in categorizing highly realistic artificial characters as real humans or artificial entities does not consider whether the human-likeness dimension is perceived continuously or categorically.

    “Notably, this suggestion itself does not yet consider whether the human-likeness dimension of the uncanny valley is perceived continuously or categorically—that is, some intermediate characters could be difficult to categorize regardless of whether increasing human-likeness were perceived as a gradual continuum or discretely as artificial and human categories.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    The naïve uncanny valley hypothesis is simplistic because it assumes that all imaginable human-likeness manipulations are equally relevant for the uncanny valley.

    “However, this hypothesis is simplistic because it assumes that all imaginable human-likeness manipulations are equally relevant for the uncanny valley.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Emotional valence is an established psychological concept that is able to incorporate both positive and negative affinity.

    “Although positive and negative affinity could be considered separately (e.g., Ho and MacDorman, 2010), emotional valence is an established psychological concept (e.g., Russell, 2003) that is able to incorporate both of them.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Russell, 2003 source

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    Premisecitation

    The two most commonly agreed upon criteria for experimental demonstrations of categorical perception are category identification and perceptual discrimination.

    “The two most commonly agreed upon criteria for experimental demonstrations of categorical perception are category identification and perceptual discrimination (Repp, 1984; Harnad, 1987).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Repp, 1984

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    • cites Harnad, 1987

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  • Classified as probably not a substantial claim.

    Interpretationreasoning

    Because human-likeness is difficult to operationalize, confounding factors and other alternative explanations could limit the conclusions that can be drawn from individual studies.

    “Because the human-likeness is difficult to operationalize, confounding factors and other alternative explanations could also limit the conclusions that can be drawn from individual studies.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    The original terms for the affinity dimension (or at least their common translations) refer to various aspects of perceptual familiarity and emotional valence.

    “A closer inspection of these terms would suggest that all of them refer to various aspects of perceptual familiarity and emotional valence.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Interpretationnone given

    Stuffed animals and toy robots could elicit positive reactions not only because they appear somewhat humanlike but because they have been purposefully designed to appear aesthetic.

    “First, stuffed animals and toy robots could elicit positive reactions not only because they appear somewhat humanlike but because they have been purposefully designed to appear aesthetic.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    Testing the core uncanny valley prediction (that almost humanlike characters elicit more negative affinity than any other characters) requires at least three human-likeness levels.

    “Because almost humanlike characters would need to be compared to both more artificial and more humanlike characters, the bare minimum for testing this prediction would be three human-likeness levels (cf. Figure 3).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing), S4 (based).

    Interpretationnone given

    Human-likeness is not a single quality of artificial characters that could be traced back to specific static, dynamic, or behavioral features; it could be varied in an almost infinite number of different ways.

    “Human-likeness is not a single quality of artificial characters that could be traced back to specific static, dynamic, or behavioral features—instead, human-likeness could be varied in an almost infinite number of different ways.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing), S4 (based).

    Interpretationreasoning

    Purposefully morbid characters would confound the more interesting effects of varying human-likeness.

    “Although purposefully morbid characters could be adopted from the original uncanny valley formulation (Mori, 2012) and used in empirical uncanny valley studies, such characters would confound the more interesting effects of varying human-likeness (Section What is Human-Likeness?).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given

    Human corpses, whether still or animate, would not evoke negative reactions only because they appear humanlike but because they are morbid and horrifying.

    “Similarly, human corpses, whether still or animate, would certainly not evoke negative reactions only because they appear humanlike but because they are morbid and horrifying.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing), S4 (based).

    Interpretationnone given

    The four most focal human-likeness levels (L1-L4) constitute the minimal set of human-likeness levels that could be used to capture the most relevant aspects of the original uncanny curve.

    “These levels constitute the minimal set of human-likeness levels that could be used to capture the most relevant aspects of the original uncanny curve.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Interpretationreasoning

    The two major dimensions of the uncanny valley-the human-likeness of stimuli and the observers' experience of affinity for them-were not defined clearly in the original uncanny valley formulation, so they could be operationalized in various different ways.

    “Because the two major dimensions of the uncanny valley—the human-likeness of stimuli and the observers' experience of affinity for them—were not defined clearly in the original uncanny valley formulation, these dimensions could be operationalized in various different ways.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S1 (asserted), S3 (load-bearing), S4 (based).

    Interpretationnone given

    Morbid characters (e.g., corpses or zombies) should evoke negative affinity.

    “Although it is quite trivial that such characters should evoke negative affinity, we have nevertheless formulated the following hypothesis to help separate morbidity effects from those of other hypotheses.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationcitation

    The original uncanny valley hypothesis was intended as a broadly applicable guideline rather than an explicit experimental hypothesis, and it is likely to be consistent with several more specific hypotheses.

    “Because the original uncanny valley hypothesis was intended as a broadly applicable guideline rather than an explicit experimental hypothesis (cf. Pollick, 2010), it is likely to be consistent with several more specific hypotheses.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Pollick, 2010 source

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  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Interpretationnone given

    Familiarity items were not considered in Ho and MacDorman (2010), although familiarity would seem to be an integral part of the uncanny valley.

    “Third, familiarity items were not considered in the study, although familiarity would seem to be an integral part of the uncanny valley.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    Some of the questionnaire items in Ho and MacDorman (2010) are not necessarily ideal for measuring their intended constructs in all contexts.

    “First, some of the questionnaire items are not necessarily ideal for measuring their intended constructs in all contexts.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Interpretationcitation

    Assuming that the uncanny valley proper coincides with the category boundary and that this boundary is considered in terms of the categorical perception framework, perceptual discrimination performance should be easier for characters at or in the close vicinity of the category boundary and not more difficult.

    “However, assuming that the uncanny valley proper is thought of as coinciding with the category boundary and that this boundary is considered in terms of the categorical perception framework, it follows (as in Cheetham et al., 2014) that perceptual discrimination performance should actually be easier for characters at or in the close vicinity of the category boundary and not more difficult.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Cheetham et al., 2014 source

      Not checked in the free run.

    • The authors state this as an assumption: The uncanny valley proper coincides with the category boundary between 'artificial' and 'human' categories.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationreasoning

    Negative affinity could be caused by mechanisms other than categorization ambiguity or categorical perception.

    “Second, negative affinity could of course be caused by some other mechanisms in addition to (or instead of) categorization ambiguity or categorical perception.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationcitation

    The eeriness factor items in Ho and MacDorman (2010) do not resemble items in typical emotion self-report questionnaires.

    “Second, although the identified eeriness factors are consistent with Mori's original terms, their constituent items (e.g., “numbing—freaky” and “unemotional—hair-rising”) do not resemble items in typical emotion self-report questionnaires (cf. self-report items in Bradley and Lang, 1994).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Bradley and Lang, 1994 source

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  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Interpretationreasoning

    The Ho and MacDorman (2010) scale is an important step toward developing a common metric for the affinity dimension.

    “Although future empirical studies might be useful for refining this scale, this work is an important step toward developing a common metric for the affinity dimension.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationreasoning

    Categorization ambiguity could lead to negative affinity even in the absence of categorical perception (i.e., when only H3a but not H3b holds true).

    “Hence, categorization ambiguity could lead to negative affinity even in the absence of categorical perception (i.e., when only H3a but not H3b holds true).”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Interpretationreasoning

    In Yamada et al. (2013), the lower pleasantness ratings for intermediate morphs could have resulted from morphing artifacts rather than intermediate human-likeness level.

    “Hence, it is possible that the lower pleasantness ratings for intermediate morphs could have resulted from morphing artifacts rather than intermediate human-likeness level.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Yamada et al., 2013 source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Interpretationcitation

    The original uncanny valley hypothesis is based on the implicit assumption that perceptual discrimination is the most difficult for characters in the uncanny valley.

    “As suggested recently by Cheetham et al. (2014), the original uncanny valley hypothesis is based on the implicit assumption that perceptual discrimination is the most difficult for characters in the uncanny valley.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Cheetham et al., 2014 source

      Not checked in the free run.

  • May combine two claims.

    Study design and conductreasoning

    The evidence from Flach et al. (2012) was considered tentative because no statistical tests had been used and the human-likeness range was constrained by the use of only CG characters.

    “We considered this evidence tentative because no statistical tests had been used; furthermore, the human-likeness range was somewhat constrained by the use of only CG characters.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Flach et al., 2012

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationcitation

    The positive uncanny valley finding in Study II in Burleigh et al. (2013) could be interpreted as evidence that some human-likeness manipulations can lead to the uncanny valley.

    “The reported positive uncanny valley finding is nevertheless important in the present context, because it could be interpreted as evidence that some human-likeness manipulations can lead to the uncanny valley.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Burleigh et al., 2013 source

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductreasoning

    Two other studies demonstrating favorable evidence for H3c were excluded from the total count because of plausible threats to validity.

    “Two other studies demonstrating favorable evidence for H3c were excluded from the total count because of plausible threats to validity.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    The non-significant finding in Burleigh et al. (2013) could have been specific to the atypical feature (rolled-back eye) used in the study.

    “Although this non-significant finding was included in the total count, it is possible that this result could have been specific to the atypical feature (rolled-back eye) used in the study.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Burleigh et al., 2013 source

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  • May combine two claims.

    Interpretationcitation

    These results strengthen the view that individuals are more sensitive and less tolerant to deviations from typical norms when judging human faces.

    “These results strengthen the view that individuals are more sensitive and less tolerant to deviations from typical norms when judging human faces.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Interpretationnone given

    Mori used corpses and zombies only as metaphorical examples when discussing threat avoidance as a possible explanation for the uncanny valley.

    “We have suggested that Mori used corpses and zombies only as metaphorical examples when discussing threat avoidance as a possible explanation for the uncanny valley.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Mori, 2012

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductcitation

    The finding from Study II in Burleigh et al. (2013) was not included as additional evidence for H1a because several other human-likeness manipulations in that study did not lead to similar findings.

    “This finding was not included as additional evidence for the hypothesis H1a, however, because several other human-likeness manipulations in this study (Burleigh et al., 2013) did not lead to similar findings.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Burleigh et al., 2013 source

      Not checked in the free run.

  • May combine two claims.

    Study design and conductcitation

    In Yamada et al. (2013), the slowest identification task response times and the most negative likability evaluations coincided, but these results were excluded because the likability evaluations could plausibly have been influenced by morphing artifacts.

    “One image morphing study (Yamada et al., 2013) demonstrated that the slowest identification task response times and the most negative likability evaluations coincided with each other; however, these results were excluded because the likability evaluations could plausibly have been influenced by morphing artifacts (cf. Section Naïve and Morbidity Hypotheses).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Yamada et al., 2013 source

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  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Study design and conductreasoning

    The present conclusions depend on the adopted evaluation criteria, which are to some extent open to subjective interpretations.

    “The present conclusions depend on the adopted evaluation criteria, which are to some extent open to subjective interpretations.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Interpretationreasoning

    The self-report items eeriness, likability, familiarity, and affinity are consistent with Mori's original formulation but are not necessarily theoretically justified.

    “although these items are consistent with the original formulation, they are not necessarily theoretically justified.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Mori's (1970) source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Study design and conductreasoning

    The present review considered only studies that operationalized affinity by self-report measures.

    “Given our inclusion criteria, we have only considered studies that have operationalized affinity by self-report measures.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    The uncanny valley could originate at least from inconsistent realism levels between individual features or from the presence of atypical features on an otherwise humanlike character.

    “Such conditions could originate, at least, from inconsistent realism levels between individual features (e.g., artificial eyes on a humanlike face) or from the presence of atypical features (e.g., atypically large eyes) on an otherwise humanlike character.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    Previous reviews have presented categorization difficulty and perceptual mismatch hypotheses separately.

    “Although previous reviews have presented categorization difficulty and perceptual mismatch hypotheses separately (e.g., Pollick, 2010)”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Pollick, 2010 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    The present review considered only the categorization ambiguity and perceptual mismatch explanations for the uncanny valley.

    “Although we have considered only the categorization ambiguity and perceptual mismatch explanations for the uncanny valley”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationown data

    The lack of a universally agreed upon operational definition for the affinity dimension is a critical issue for uncanny valley studies.

    “The lack of universally agreed upon operational definition for the affinity dimension is a critical issue for uncanny valley studies.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S1 (asserted), S3 (load-bearing).

    Interpretationreasoning

    The level of visual distortions produced by morphing increases toward the middle of generated human-likeness continua.

    “the level of visual distortions produced by morphing would hence increase toward the middle of the generated human-likeness continua.”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: Morphing artifacts are a realistic concern.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductreasoning

    The minimal human-likeness levels specified for testing each hypothesis should not be taken as practical guidelines for empirical studies.

    “These minimal levels should hence not be taken as practical guidelines for empirical studies.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    Although not any kind of human-likeness manipulation leads to the uncanny valley, the uncanny valley could be caused by more specific perceptual mismatch conditions.

    “Taken together, the present review suggested that although not any kind of human-likeness manipulation leads to the uncanny valley, the uncanny valley could be caused by more specific perceptual mismatch conditions.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    The present conceptual analysis relied on the English translation and other secondary sources instead of the original Japanese article.

    “A plausible limitation related to our conceptual analysis of the original uncanny valley formulation (Mori, 2012) is that we have relied on its English translation and other secondary sources instead of the original article written in Japanese.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Mori, 2012

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing). May combine two claims.

    Study design and conductreasoning

    The adopted evaluation criteria cannot and should not be taken as evidence for the experimental validity of the evaluated studies themselves.

    “Because all possible aspects of experimental validity were not covered, the adopted criteria cannot and should not be taken as evidence for the experimental validity of the evaluated studies themselves.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given

    Perceptual familiarity and emotional valence are clearly separate constructs.

    “these constructs are clearly separate from each other”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Categorization ambiguity and frequency of exposure to specific within-category stimuli contribute independently to the uncanny valley.

    “Burleigh and Schoenherr (2015) extend this idea by demonstrating that categorization ambiguity and the frequency of exposure to specific within-category stimuli contribute independently to the uncanny valley.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Burleigh and Schoenherr (2015)

      Not checked in the free run.

55 of 55

  • The authors state this as an assumption.

    The uncanny valley proper coincides with the category boundary between 'artificial' and 'human' categories.

    “assuming that the uncanny valley proper is thought of as coinciding with the category boundary”

  • The authors state this as an assumption.

    Identification uncertainty at the category boundary leads to negative affinity.

    “The most straightforward assumption would be that identification uncertainty at the category boundary (“categorization ambiguity”) leads to negative affinity.”

  • The authors state this as an assumption.

    Perceptual discrimination is more difficult for characters in the uncanny valley.

    “Assuming that perceptual discrimination would be more difficult for characters in the uncanny valley, this difficulty should also be associated with negative affinity.”

  • The authors state this as an assumption.

    Morphing artifacts are a realistic concern.

    “Assuming that morphing artifacts were a realistic concern”

  • The paper relies on this without support.

    The experimental stimuli clearly represented phenomena that would be likely to exist also in the real world.

    “given that the experimental stimuli clearly represented phenomena that would be likely to exist also in the real world”

  • The paper relies on this without support.

    This article is the first systematic review of the empirical evidence for the uncanny valley.

    “to our knowledge, this article is the first systematic review of the empirical evidence for the uncanny valley.”

  • The paper relies on this without support.

    No prior distinction has been made between different perceptual mismatch hypotheses.

    “we are not aware that a further distinction would have been made between different perceptual mismatch hypotheses.”

  • The paper relies on this without support.

    The original uncanny valley formulation proposed that movement would amplify the characteristic uncanny curve.

    “The original uncanny valley formulation proposed that movement would amplify the characteristic uncanny curve.”
8 of 8

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

Cites

Flagged first, then by citations

Research works printed but not linked: 6

  1. Brenton, 2005, The uncanny valley: does it exist?
  2. Hanson, 2005, Expanding the aesthetic possibilities for humanoid robots,
  3. Hanson, 2006, Exploring the aesthetic range for humanoid robots,, 16
  4. Harnad, 1987, Introduction: psychophysical and cognitive aspects of categorical perception: a critical overview,, 1
  5. Ishiguro, 2006, Android science—toward a new cross-interdisciplinary framework, Interact. Stud, 7, 297, 10.1075/is.7.03mac · DOI
  6. Ramey, 2005, The uncanny valley of similarities concerning abortion, baldness, heaps of sand, and humanlike robot,

Cited by

Sorted by citations

Related

Authors
Kätsyri, J., Förger, K., Mäkäräinen, M., & Takala, T.
Affiliations
Aalto University (FI)
ORCID
Takala, Tapio
Venue
Frontiers in Psychology
Publisher
Frontiers Media SA
Published
2015-04-10
Volume
6
Pages
390-390
ISSN
1664-1078 (ISSN-L)
DOI
10.3389/fpsyg.2015.00390
PMC
PMC4392592
OpenAlex
W2094482505
Semantic Scholar
af7b3323c7f3b80c3da6c0be78a85475aad1354a
Cited by
500
References
73
Citations by year
2026: 71 · 2025: 67 · 2024: 76 · 2023: 36 · 2022: 65 · 2021: 47 · 2020: 27 · 2019: 35 · 2018: 34 · 2017: 21 · 2016: 16 · 2015: 3 · 2014: 1
FWCI
3.85
Type
journal article
Language
en
Open access
Licence
cc-by
Locations
  • Frontiers in Psychology (publishedVersion, cc-by)
  • Europe PMC (PubMed Central) (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • Aaltodoc (Aalto University) (submittedVersion, cc-by)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion)
Topics
  • Social Sciences › Psychology › Social Psychology › Social Robot Interaction and HRI
  • Physical Sciences › Computer Science › Human-Computer Interaction › Virtual Reality Applications and Impacts
  • Life Sciences › Neuroscience › Cognitive Neuroscience › Face Recognition and Perception
Keywords
uncanny valley, eeriness, anthropomorphism

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-09.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-09.

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