The Uncanny Valley (不気味の谷現象)
The Uncanny Valley (不気味の谷現象)
The Uncanny Valley (Japanese: 不気味の谷現象, Bukimi no Tani Genshō) is a hypothesized relationship between the degree of an object's resemblance to a human being and the emotional response to that object. As a robot or animated character becomes more human-like, observers' emotional responses become increasingly positive and empathetic, until a point where the response suddenly shifts to strong revulsion.
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Introduction and Etymology
The concept of the Uncanny Valley was first introduced in 1970 by Japanese roboticist Masahiro Mori in his essay Bukimi no Tani.[1] Mori charted the relationship between human likeness and human affinity, noting that while familiarity and comfort initially increase as an entity looks more human, they violently plummet just before absolute realism is achieved.
The term "uncanny" in Western psychology traces back to Ernst Jentsch's 1906 essay On the Psychology of the Uncanny and Sigmund Freud's 1919 essay The Uncanny (Das Unheimliche).[2] Freud described the uncanny as something that is strangely familiar, rather than simply mysterious, triggering cognitive dissonance because it belongs simultaneously to the known and the unknown.
The Theoretical Curve
Mori's original hypothesis is traditionally visualized as a graph where the x-axis represents "Human Likeness" (from an industrial robot to a healthy human) and the y-axis represents "Affinity" (familiarity or comfort level).
Mori theorized that movement amplifies the uncanny effect. A static wax figure might dip slightly into the valley, but a moving, highly realistic animatronic or puppet will fall much deeper into the valley, causing profound revulsion if its kinetic movements do not perfectly match its biological appearance.[1:1]
Key Milestones on the Curve:
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Ascending Peak: Humanoid robots (e.g., ASIMO) or stylized cartoon characters. They possess human features but are distinctly non-human, eliciting empathy.
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The Valley: Zombies, corpses, highly realistic prosthetics, and advanced humanoid androids. They look almost perfectly human, but subtle imperfections (in skin texture, micro-expressions, or eye movement) trigger deep unease.
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Second Peak: Healthy, living human beings.
Proposed Explanations
Researchers across psychology, neuroscience, and evolutionary biology have proposed several mechanisms to explain why the Uncanny Valley exists.
1. Evolutionary & Biological Triggers
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Pathogen Avoidance: Entities in the uncanny valley often feature unnatural skin tones, jerky movements, or vacant stares. From an evolutionary perspective, these are visual cues associated with infectious disease, severe genetic mutation, or death. The revulsion is an adaptive response to avoid potential pathogens.[3]
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Mortality Salience: Highly realistic but lifeless entities (like androids or wax figures) act as subconscious reminders of death, triggering an innate biological fear of corpses.[1:2]
2. Cognitive & Psychological Mechanisms
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Violation of Expectation (Predictive Coding): The human brain constantly makes predictions based on sensory input. When an entity looks highly human, the brain activates an expectation of fluid, biologically accurate movement and micro-expressions. When the entity moves with mechanical stiffness, it causes a severe mismatch in predictive coding, resulting in cognitive discomfort.[4]
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Categorization Boundary: The human mind relies on distinct categories to process the world (e.g., "human" vs. "machine"). Entities in the valley blur this boundary, creating conflicting neural signals as the brain struggles to categorize what it is looking at.[5] This makes the uncanny valley android a kind of simulacrum — a copy so close to the original that the distinction between real and artificial collapses, echoing Baudrillard's hyperreality.
Real-World Examples
"I have noticed that, in climbing toward the goal of making robots appear human, our affinity for them increases until we come to a valley, which I call the uncanny valley." — Masahiro Mori
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Robotics: Androids designed by researchers like Hiroshi Ishiguro (such as the Geminoid series) or Hanson Robotics (such as Sophia) are frequently cited as residing squarely in the uncanny valley due to minor discrepancies in their facial actuators and eye tracking.
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Film & Media: Early attempts at photorealistic CGI humans in cinema often triggered widespread uncanny valley complaints. Notable examples include the animated film The Polar Express (2004) and the digital rejuvenation of actors in modern franchises, where "dead eyes" break the illusion of life.
Are there specific applications of the Uncanny Valley—such as in video game design or modern artificial intelligence avatars—that you would like to explore next?
See Also
- Déjà Vu — Both the uncanny valley and déjà vu involve a mismatch between perceived familiarity and objective reality. In the uncanny valley, a near-human entity triggers revulsion; in déjà vu, a novel situation triggers an inappropriate sense of familiarity. Both are cognitive glitches in the brain's familiarity-detection system.
References
Masahiro Mori / The Uncanny Valley / IEEE Robotics & Automation Magazine ↩︎ ↩︎ ↩︎
Karl MacDorman / Subjective ratings of robot video clips for human likeness, familiarity, and eeriness / ScienceDirect ↩︎
Ayse Pinar Saygin et al. / The thing that should not be: predictive coding and the uncanny valley / Oxford Academic ↩︎
Thalia Wheatley / The uncanny valley: kinematics and human-likeness / PubMed ↩︎