by Jonah Ruddock
In the 1970s, roboticist Masahiro Mori hypothesized that as an object becomes increasingly human-like in appearance, viewers will feel increasingly empathetic and positive towards it. However, this correlation does not continue forever. Once the object reaches a certain point of human imitation, viewers will respond with a sense of fear, disgust, and anxiety. This dip, where empathy turns to apathy and an impression of warmth gives way to one of chilling eeriness, is what he calls the uncanny valley.
Examples of the uncanny valley are most often found in automatons, wax mannequins, and CGI and animated characters. In efforts to avoid this, animators sometimes deliberately manipulate the features of characters in order to reduce their realism. Mori intended this idea more as a guideline for his fellow designers than as a scientific statement, but it has generated a good deal of curiosity and formal study, especially in the mid-2000s.
No one knows for certain why this happens, but we will go over a few theories here. One is that figures outside of the uncanny valley are easily distinguishable as non-human, which makes their limited human qualities (e.g. a smiley face drawn on a rock, the mannerisms of a cartoon character), seem endearing or amusing. In contrast, figures inside the valley can be called non-human with less confidence. Their non-human qualities are amplified as the things that do not fit in (e.g. stunted movements or inexpressive eyes in an otherwise realistic android), which leads us to perceive them as disfigured or strange. Some have suggested our discomfort toward figures judged not as non-human but as unhealthy or abnormal humans has an evolutionary basis. Rhodes and Zebrowitz theorize that seeing a humanoid object in the valley triggers a disgust response as a form of protection against pathogens. In their 2002 paper Facial Attractiveness: Evolutionary, cognitive, and social perspectives, they write, “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.” The argument that the uncanny valley can be explained better from a biological standpoint than a cultural one seems to be reinforced by studies on primates done by scientists at Princeton University in 2009. The researchers, led by Asif Ghazanfar, presented monkeys with three pictures: one of a realistic monkey, one of an unrealistic, cartoonish monkey, and one that was a combination of the two. The monkeys preferred both the unrealistic and realistic monkeys over the synthesis (their preference was measured by gaze time), suggesting that the uncanny valley is not unique to humans.
Still, there is merit in psychological arguments as well. Another possible explanation for negativity inspired by figures in the valley is the cognitive dissonance created by the difficulties of categorizing something that seems to exist in the overlap between human and non-human. Neither category inspires dread on its own, but a transience between the two does. What the brain wants to see is consistency: if something looks human, it should be that fully. This is why so many androids exist in the valley. To look convincingly human is an achievable task, but mastering the fluidity of human movements and facial expressions is more challenging, and there are always tells that break the illusion. Studies have shown that robots with human-like voices and humans with robotic voices were both perceived as far more disturbing than the usual pairings. Robots that appear human-like are expected to be more intelligent than robots that are not, and when this expectation is undermined, it creates unease.
Some have also suggested that seeing figures in the uncanny valley taps into our innate fear of death. Seeing prosthetic limbs or androids in partial disassembly can elicit a fear of mutilation and torture. It can also surface a fear that the people around us are not what they seem and are instead lacking real depth or substance. An even more cultural basis for this effect is found in the theory that seeing nearly-human but non-human figures threatens our identity as “special” organisms that are somehow above the baser facts of life, or simply threaten our sense of personal individuality.
Whether stemming from a perceived disruption of the Great Chain of Being or an evolutionary predisposition to avoid lingering around corpses and the diseased, the uncanny valley is a fascinating phenomenon that has considerable effects on robotics and media production.