We can all agree that the “nearly human-like but not exactly there yet” appearance of clowns, dolls and zombies are terrifying. This “too close to humans but not quite” look that leads to the feeling of unease is known as “uncanny valley.” The uncanny valley hypothesis originated in an essay by Masahiro Mori published in 1970. According to his research, as human likeness increases in an object, so does one’s affinity for the object. However, at some point as likeness increases, affinity drops dramatically, creating a “valley” in affinity.
But why?
There are many hypotheses that exist to explain the uncanny valley phenomenon (all with varying degrees of evidence) and so, I’ve compiled my top three theories on why we experience the uncanny valley. Don’t worry, there’ll be no uncanny pictures ahead!
- . DISEASE AND MATING THEORY
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Diekhof et al. (2025) refer to the disease theory as the “Pathogen Avoidance Hypothesis.” This hypothesis proposes that the evoked feelings of discomfort, fear and disgust are based on a cognitive mechanism that originally evolved to “motivate pathogen avoidance” (Diekhof et al., 2025). The imperfections seen in uncanny valley figures (enlarged eyes, widened smiles, etc.) are perceived as cues of a transmissible disease, eliciting a reaction not from the figure itself but the idea of catching the carried “disease” (Diekhof et al., 2025). Like the disease theory, the mating theory hypothesizes that the existing imperfections in uncanny valley figures evoke a cognitive mechanism to avoid mates with health issues based on visual features (Rhodes & Zebrowitz, 2002).
This theory also follows the idea that feelings of fear and discomfort stem from an evolutionary concern about our personal fitness (survival and reproductive ability). In a discussion about uncanny valley from a scientific perspective, I personally find these theories to be the most plausible. They share the same overarching concept, that we experience the uncanny valley due to an evolutionary mechanism to protect our fitness, which seems to be the most logical hypothesis (thanks to the extensive scientific evidence supporting the theory).
- . CONFLICTING PERCEPTUAL CUES
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Urgen et al. (2018) explains that human-like appearance results in our brains predicting human-like behavioUrs and movements. Therefore, an uncanny valley occurs when those predictions are not met, such as when we encounter human-like forms but non-human movements/behavioUrs. For example, the ridged movements of robots or the odd zombie-walk provide a sense of eeriness due to the conflicting perceptual cues of human appearance and non-human movements. It’s this conflict that creates a fearful response as we try to grapple with exactly what we’re facing.
Is the figure human? And therefore friendly? Or should I be scared and wary?
Scenes in horror movies such as Smile or Us and Weapons, where an uncanny figure appears to be harmlessly standing in frame, have always frightened me more than the scenes with jump scares. It’s unsettling to grapple with the idea that this friendly-looking creature is actually a foe. Since I can relate to this theory on a personal level, it feels plausible to me, and it captured my initial guess on the reason behind the uncanny valley (at least for me personally).
- . MIMIC THEORY
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While not supported by any scientific evidence, the mimic theory is fairly talked about on social media and also the most fun and imaginative. The mimic theory suggests that in the past, humans may have been hunted by creatures that evolved to mimic human behavior/appearance. Again, while this theory isn’t supported by any evidence, it makes fun speculation and chatter, serving more as a Creepypasta rather than a serious speculation. As a Creepypasta fan, this theory is one of my favourites just for its virality and for the fun conversations it can bring up. As a bonus, this theory has resulted in some fun, creepy, and unique artwork depicting the mythical mimic.
Though these three theories are my favourite, there are many explanations for why we experience the uncanny valley. Each theory is unique and provides an entertaining deep dive, so don’t stop your journey here! Just beware of uncanny pictures ahead!