Uncanny valley is a hypothesis which explains the feeling of revulsion in human nature. If you see something that looks real, but you know it isn't, because there is probably something abnormal, be it in looks, actions, or movements, it will creep you out. This is scarier than ghosts that we have heard of, or watched on t.v., because most of us don't believe in them. But creating uncanny stuff is a real thing. There exist such robots that absolutely look like humans, but if we find even a wee bit difference, our mind doesn't accept them, causing the feeling of fear and disgust. The difference in the appearance and motion of a robot between being "barely human" and "fully human" constitutes the uncanny valley. The term was coined in 1970 by Dr. Masahiro Mori, a robotics professor. The hypothesis originally stated that as robots are made human-like, our feelings towards them might be positive and empathetic, but beyond a limit, this feeling of positiveness and empathy will change into strong revulsion, as it eventually depends on the appearance of the robot. This revulsion can be strong for few, whereas none for others. Imagine this robot, that has the features of a beautiful woman, yet its colors and appearance are strange, differentiating it from humans. Now imagine that she comes to you and talks in perfect human voice!! You'd be completely stunned for a moment, wouldn't you? Dr. Masahiro Mori put forth a question, that how would we react if human-looking robots were made. Would we be easily able to connect to them and accept their existence? Or after a certain limit, when the robot looks very much human-like, would our feelings change from acceptance to rejection? He supported the latter comment because imitating humans only in looks is not enough for us to relate to them. The change in their movement is not real. He named this change in feelings as "bukimi no tani" meaning "uncanny valley". The Japanese words are a literal translation into English. Bukimi - eerie/ strange/ uncanny, no - is a connecting participle, tani - valley.

Several theories have been proffered to explain human's cognitive process behind this hypothesis. Mate Selection This theory states that, when we encounter a situation manifesting uncanny stimulus (something strangely absurd), we develop a feeling of aversion towards it, because our evolved cognitive process (mind functions - thinking, calculating, etc.) wants to avoid low fertility, poor hormonal health, or ineffective immune systems that can be seen and understood by the physical appearances of the stimuli. Violation of human norms The uncanny valley might "be symptomatic of entities that elicit a model of a human other but do not measure up to it" - (MacDorman & Ishiguro, 2006). This means that humans might have empathy towards something that looks a little bit human, since in this case its human qualities will be noticeable. But for those entities that look almost like humans, their non-human qualities will come into notice, creating in our minds the picture of a human other (other species), creeping within us the feeling of strangeness. If we look at it this way, we can say, that here the perspective of looking at a robot trying to act like a human is changed to a human who is failing to act like a human! Wouldn't you be freaked out for a minute to see this mannequin standing outside a store motionless? Mortality salience It states that, an uncanny robot, stimulates the fear of death and its inevitability. Partially disassembled robots insinuate our subconscious fears of reduction, replacement, and annihilation. 1. The mask of a human and the insides of a machine, this scares us to contemplate that we in fact might be just soulless beings like them. 2. The dis-assembly, mutilation, and decapitation of robots reminds us of the after-war/conflict effects, making us realize we are mortal. 3. Mostly humanoids are made as a replication of some existing people, which creates a fear of being replaced by their doppelgangers in their real lives. 4. The movements of a robot are not smooth and show jerkiness, stimulating a fear of losing our body control. Pathogen avoidance There is a cognitive process that evolved to avoid the potential sources of pathogen (anything that can produce disease) by evoking a strong emotion of disgust. This cognitive process gets activated when we encounter an uncanny stimulus. "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." - (Rhodes, G. & Zebrowitz, L. A. (eds) (2002). Facial Attractiveness: Evolutionary, Cognitive, and Social Perspectives, Ablex Publishing.) This tells us that the visual appearance of a robot and a human animation gives the effects of a corpse or a diseased person eliciting the feeling of disgust. Sorites paradoxes This theory states that whenever we see the attributes of a human or a non-human, our senses are sabotaged by comparing the qualitative differences in categories with quantitative metric and degree of human likeness. Religious definition of human identity Few religions, mainly those of the Abrahamic religions (Christianity, Judaism, and Islam), have a belief that imitation of humans is a threat to human distinctiveness. This is a belief caused due to a concept known as existential anxiety originating from death. A psychiatrist Irvin Yalom states that humans develop this kind of psychological defenses in order to avoid existential anxiety. Conflicting perceptual cues The negative feeling associated with the uncanny valley is due to the conflict in the perception cues in our cognitive process. When we see a humanoid moving like a robot, we undergo a perceptual tension causing psychological discomfort, i.e. eeriness. Theories have proved that a person observing a human-looking robot is way much disturbed than a person observing a machine-looking robot.

In this diagram we see, that human likeness and familiarity is 100% for a healthy person, but goes negative when it comes to prosthetic limbs, zombie and corpse which form the uncanny valley. Stuffed toys, humanoids and industrial robots are something we are to an extent familiar with.

The concept of uncanny valley remained sidelined for almost 30 years, until technology took charge on making realistic robots and animations. Mori's hypothesis came into consideration for all the movie animators, in an attempt to making life like animation. The advice to them was to make graphics keeping in mind the human emotions and its impact on them, which shouldn't fall in the negative valley of the graph. Some animation examples The realization of taking the uncanny valley hypothesis seriously dawned upon the film industry after the negative effect the 1988 short film "Tin Toy" by Pixar had on the public. Next in line was the 2004 animated film "the polar express". This was another perfect example of animation falling into the uncanny valley. It was unpleasant to watch and the children in the film gave a feeling of eeriness throughout. People reviewed it as a train of zombies, being creepy and uncanny, with dead eyes and weird eyebrows which could've changed the whole look of the children making it bearable to watch. A 2007 animated film Beowulf, was criticized for failing the uncanny valley test, wherein the hero looked scarier than the villain in the whole movie. In a 2010 film The Last Airbender, there is a flying bison called Appa, whose physical appearances have been changed even though slightly but creepily making it "uncanny". A normal bison has its eyes on the side of its head, which had been moved to the front without changing the rest of its facial structure making it fall deep into the uncanny valley. The 2011 film 'Mars Needs Moms' had a different style of animation making it widely reviewed as creepy and unnatural. Contradicting all the above movies the 2011 animated movie 'The Adventures of Tintin', cleared the test of the uncanny valley being highly praised by the public and the critics. Kevin Kelly, the editor of the Wired Magazine wrote in appreciation of the film, "we have passed beyond the uncanny valley into the plains of hyperreality."

Some design principles have been proposed to avoid animation falling into the uncanny valley. Design elements should match in human realism There shouldn't be a robot with a human voice and there shouldn't be a human with a synthetic voice. Both these concepts are very creepy. Similarly, a robot having smooth movements like a human can definitely creep you out, and so can a normal human walking mechanically. Human neuroimaging studies propose that matching appearance and motion kinematics are important. Reducing conflict and uncertainty by matching appearance, behavior, and ability When you encounter a robot, there will be only certain things you would expect it to do. If it starts doing more than that, you might start having a problem in your cognitive process. Same is the case with a human, from whom you would expect everything a normal human can. If robots are probably made to look and act like robots they will have a less discomforting level with humans, because it will certainly reduce the conflict and uncertainty of its being! Human facial proportions and photorealistic texture should only be used together Generally in animation, cute effect is given by making the eyes look really big, but these effects shouldn't be given with photorealistic texture. This if you can imagine right now, looks exceptionally creepy in your head, doesn't it? So if an animation has a photorealistic texture, it needs to have proper human facial proportions. These human-like dolls that look like real babies can be unnerving to look at. With eyes so real, and rest of the part looking like real skin, yet synthetic when you touch it, is just so spooky. I wonder why do they even manufacture such toys! These two animated images are simply weird and creepy. Reason is that a dog is given the face of a man, with eyes, lips and beard, and the creature on the right has the face of a man, whereas hands and legs of an alien, with no body! Hence, the above design rules need to be followed, in order to avoid the creepiness in creating animation and even toys!

Good planning may raise human-looking objects out of the valley David Hanson, a robotics designer accursed Mori's theory that the existence of objects that look like humans must always be considered uncanny inevitably. He sighted that the uncanny valley that Karl MacDorman and Hiroshi Ishiguro created - by taking experiences of participants that rated those pictures negative that morphed from humanoid androids to humans - might be flattened out by appending Neoteny|neotenous, cartoonish features to the objects that had previously fallen into the valley. The uncanny appears at any degree of human likeness David Hanson also proposed an idea that the uncanny effect is mainly based on how the brain responds to a situation depending on the categorical perception that is cognitively processed with the available information. For example, people suffering from Capgras syndrome, which is a rare condition in which they believe, that a real human has been replaced by a robot, since even though it looks completely like that human, there are changes in its emotional responses. The uncanny valley is a heterogeneous group of phenomena The phenomenon that is considered to be in the uncanny valley is diverse, and highly depends on the cultural background of a person, to accept the existence of a robot that looks like a human. The uncanny valley may be generational This phenomenon may decrease with every coming generation as children of this age are more familiar with computer graphics, robots and humanoids. For them, there might not exist an uncanny valley, because their cognitive process is so familiarized with the concept of robotics, that it does not occur to them as weird or strange.