Uncanny Valley: Encyclopedia - Uncanny Valley

Uncanny Valley

The Uncanny Valley is a principle of robotics concerning the emotional response of humans to robots and other non-human entities. It was theorized by Japanese roboticist Masahiro Mori in 1970. The principle states that as a robot is made more humanlike in its appearance and motion, the emotional response from a human being to the robot will become increasingly positive and empathic, until a point is reached at which the response suddenly becomes strongly repulsive; as the appearance and motion are made to be indistinguishable to that of human being, the emotional response becomes positive once more and approaches human-human empathy levels.

This gap of repulsive response aroused by a robot with appearance and motion between a "barely-human" and "fully human" entity is called the Uncanny Valley. The name harkens to the notion that a robot which is "almost human" will seem overly "strange" to a human being and thus will fail to evoke the requisite empathetic response required for productive human-robot interaction.

The phenomenon can be explained by the notion that if an entity is sufficiently non-humanlike, then the humanlike characteristics will tend to stand out and be noticed easily, generating empathy. On the other hand, if the entity is "almost human", then the non-human characteristics will be the ones that stand out, leading to a feeling of "strangeness" in the human viewer.

Another possibility is that infected individuals and corpses exhibit many visual anomalies similar to the ones we see with humanoid robots and so we react with the same alarm and revulsion. The reaction may in fact become worse with robots since there is no overt reason for it to occur; when we see a corpse we understand where our feelings come from. Behavioural anomalies too are indicative of illness, neurological conditions or mental dysfunction, and again evoke acutely negative emotions.

Some roboticists have heavily criticized the theory, arguing that Mori had no basis for the right part of his chart, as human-like robots are only now technically possible (and still only partially). David Hanson, a roboticist who developed a realistic robotic copy of his girlfriend's head, said the idea of the Uncanny Valley was "really pseudoscientific, but people treat it like it is science." Sara Kiesler, a human-robot interaction researcher at Carnegie Mellon University, questioned Uncanny Valley's scientific status, noting that "we have evidence that it’s true, and evidence that it’s not."

Uncanny Valley - Valley of familiarity

There are mathematical functions of the form y = f(x) for which the value of y increases (or decreases) continuously with the value of x. For example, as the effort x increases, income y increases, or as a car's accelerator is pressed, the car moves faster. This kind of relationship is ubiquitous and easily understood. In fact, it covers most phenomena, so we might think that this function can represent all relations. That is why people are usually upset when faced with some phenomenon it cannot represent.

Climbing a mountain is an example of a function that does not increase continuously: a person's altitude y does not always increase as the distance from the summit decreases owing to the intervening hills and valleys. I have noticed that, as robots appear more humanlike, our sense of their familiarity increases until we come to a valley. I call this relation the "uncanny valley."

Recently there are many industrial robots, and as we know the robots do not have a face or legs, and just rotate or extend or contract their arms, and they bear no resemblance to human beings. Certainly the policy for designing these kinds of robots is based on functionality. From this standpoint, the robots must perform functions similar to those of human factory workers, but their appearance is not evaluated. If we plot these industrial robots on a graph of familiarity versus appearance, they lie near the origin (see figure below). So they bear little resemblance to a human being, and in general people do not find them to be familiar. But if the designer of a toy robot puts importance on a robot's appearance rather than its function, the robot will have a somewhat humanlike appearance with a face, two arms, two legs, and a torso. This design lets children enjoy a sense of familiarity with the humanoid toy. So the toy robot is approaching the top of the first peak.

Of course, human beings themselves lie at the final goal of robotics, which is why we make an effort to build humanlike robots. For example, a robot's arms may be composed of a metal cylinder with many bolts, but to achieve a more humanlike appearance, we paint over the metal in skin tones. These cosmetic efforts cause a resultant increase in our sense of the robot's familiarity. Some readers may have felt sympathy for handicapped people they have seen who attach a prosthetic arm or leg to replace a missing limb. But recently prosthetic hands have improved greatly, and we cannot distinguish them from real hands at a glance. Some prosthetic hands attempt to simulate veins, muscles, tendons, finger nails, and finger prints, and their color resembles human pigmentation. So maybe the prosthetic arm has achieved a degree of human verisimilitude on par with false teeth. But this kind of prosthetic hand is too real and when we notice it is prosthetic, we have a sense of strangeness. So if we shake the hand, we are surprised by the lack of soft tissue and cold temperature. In this case, there is no longer a sense of familiarity. It is uncanny. In mathematical terms, strangeness can be represented by negative familiarity, so the prosthetic hand is at the bottom of the valley. So in this case, the appearance is quite human like, but the familiarity is negative. This is the uncanny valley.

On close observation, a bunraku puppet is not very similar to human beings. Its realism in terms of size, skin, and so on, does not approach that of a prosthetic hand. But when we enjoy a puppet show in the theater, we are seated far from the puppets. Their absolute size is ignored, and their total appearance including eye and hand movements is close to that of human beings. So although the puppets' body is not humanlike, we can feel that they are humanlike owing to their movement. And from this evidence I think their familiarity is very high.

Uncanny Valley - Effects of movement

For creatures, including robots, movement is generally a sign of life. As shown in the figure above, adding movement changes the shape of the uncanny valley by exaggerating the peaks and valley. For the industrial robot, the impact of movement is relatively slight because we see it as just a machine. If it stops moving, it just stops working. But if programmed properly to generate humanlike movements, we can enjoy some sense of familiarity. Humanlike movement requires similarity of velocity and acceleration. Conversely, if we add movement to a prosthetic hand, which is at the bottom of the uncanny valley, our sensation of strangeness grows quite large. Some readers may know that recent technology has enabled prosthetic fingers to move automatically. A commercially available prosthetic hand made with the highest technique was developed in Vienna. To explain how it works, the intention to move the forearm, even if missing, produces current in the arm muscles that can be detected by an electromyogram. So the prosthetic hand detects the current by means of electrodes and amplifies the signal to activates a small motor in the prosthetic arm to move the fingers. This hand can move in a way that causes some healthy people to feel uneasy. If you shook a woman's hand with this hand in a dark place, the woman must be shocked!

Since these effects are apparent for just a prosthetic arm, the strangeness will be magnified if we build an entire robot. You can imagine going to a work place where there are many mannequins: if a mannequin started to move, you might be shocked. This is a kind of horror.

In the World Expo held in Osaka this year, the robots displayed a more elaborate design. For example, one robot has 29 artificial muscles in the face to make humanlike facial expressions. According to the designer, laughing is a kind of sequence of face distortions, and the distortion speed is an important factor. If we cut the speed in half, laughing looks unnatural. This illustrates how slight variations in movement can cause a robot, puppet, or prosthetic hand to tumble down into the uncanny valley.

Uncanny Valley - Escape by design

We hope to design robots or prosthetic hands that will not fall into the uncanny valley. So I recommend designers take the first peak as the goal in building robots close to the first peak rather than the second. Although the second peak is higher, there is a far greater risk of falling into the uncanny valley. We predict that it is possible to produce a safe familiarity by a non-humanlike design. So designers please consider this point. A good example of this theory in practice is glasses. Glasses do not resemble the real eyeball, but this design is adequate and can make the eyes more charming. This is not a new theory, either. Artists who make statues of Buddhas created a model of a human hand that is made from wood. The fingers bend at their joints, but the hand has no finger prints and it assumes the natural color of wood. Observers of this art think that it is beautiful and there is no sense of the uncanny.

Uncanny Valley - The significance of the uncanny

In the familiarity graph above, a healthy person is at the top of the second peak. And when we die, we fall into the trough of the uncanny valley. Our body becomes cold, our color changes, and movement ceases. Therefore, our impression of death can be explained by the movement from the second peak to the uncanny valley as shown by the dashed line in the figure. We might be happy this line is into the still valley of a corpse and that of not the living dead! I think this explains the mystery of the uncanny valley: Why do we humans have such a feeling of strangeness? Is this necessary? I have not yet considered it deeply, but it may be important to our self-preservation.

We must complete the map of the uncanny valley to know what is human or to establish the design methodology for creating familiar devices through robotics research.

Uncanny Valley - The Uncanny Valley in film

Although originally resulting from experimental data and applied only to robotics, the principle has been applied to computer animation characters. American film critic Roger Ebert has applied the notion of Uncanny Valley to the use of make-up and costumes of humanoid creatures in movies.

The Uncanny Valley was considered by some to be the reason behind the difficulty in creating computer-animated characters. Critics of computer animated films sometimes invoke the Uncanny Valley when explaining their dislike for a particular film. The principle leads to the conclusion that to generate a positive emotional response in human beings, it is often better to include fewer human characteristics in the entity, lest it fall into the Uncanny Valley. Critics argue, however, that there has been no evidence in animation or filmmaking for the existence of the Uncanny Valley, even though movie effects have gradually developed to the point when humans are digitally rendered realistically and without evoking negative emotions from the viewers. Proponents of this view argue that nowhere between 1970s and 2000s have moviemakers actually faced the challenge of the Valley. One counterpoint to the denial of the existence of the Valley in films is the early Pixar production Tin Toy. There, the baby shown is fully computer generated yet looks less than human and can prove frightening or unpleasant to children. The effect is lessened by the two dimensional nature of the character, but the overly defined wrinkles and (comparatively) primitive rendering of the spittle makes the character appear evil or otherwordly. A similar effect is seen in the doll's head character in the film Toy Story. The character can be again frightening to children because it is in essence a mobile deformed human head. Even if it is not frightening, most children prefer the cute appeal of the aliens or indeed Woody because there is less human resemblence.

In 2001, Square Pictures' photorealistic movie, Final Fantasy: The Spirits Within failed at the box-office and is often cited as a possible victim of the Uncanny Valley. The movie was the first major wide-released CGI film to feature photorealistic characters, and in turn brought about quite a bit of attention from movie critics and filmmakers alike. The Uncanny Valley theory is thought to be most prominent in Final Fantasy's character movements. The characters also lack any visible perspiration, as well as eye and lip movements that seem "off" - probably two of the most difficult techniques to accomplish in computer animation.

It has been said the best way to accomplish convincing human movements and to "jump" the Uncanny Valley in computer animation is to combine both motion capture and keyframing techniques. Though the former has become a popular technique, keyframing is still widely used throughout the animation industry. The film adaptation of J.R.R. Tolkien's The Lord of the Rings, which features the character Gollum, uses this combined technique with stunning results. Note, however, that Gollum's eyes and face were animated using only keyframing. Note also that the Gollum animation also featured advances in modelling (including skin texture, and effects such as saliva around lips) which allow the character's external appearance to reach the other side of the Valley. One obvious caveat with Gollum, however, is that the character is evidently non-human (and indeed intentionally uncanny to start with) and so may not trigger the same response as a human figure would when modelled using the same techniques.

Despite advances in computer animation, some feel the Uncanny Valley affected two CGI films of 2004, The Incredibles and The Polar Express. The close dates of release led to many critics' comparison of the two movies, with some preferring the deliberately stylized appearance of the characters in The Incredibles over the more human-like characters in The Polar Express (which were described by many critics as being "disturbing"). Pixar stated that the reason for stylizing the characters in the "Incredibles" was not due to an inability to make the characters more realisitic, but an attempt to avoid the Uncanny Valley.

The CG animation Final Flight of the Osiris in the Animatrix also suffers from this - although, as this was also made with the same techniques as in Final Fantasy: The Spirits Within, it was in some ways expected to. Erotic sequences with Uncanny Valley characters, as featured in Final Flight, are particularly disturbing, since they provide conflicting messages of "this is arousing" and "this is non-human".

The Uncanny Valley is also a plot point in some movies about robotics. "A.I.: Artificial Intelligence" centers on a future where many people are disturbed at how realistic the new line of androids is. For example, a rowdy crowd that rejoices in watching robot destruction derbies called "Flesh Fairs" falls silent when the next subject about to be ripped apart appears to be an adorable human boy. In "I, Robot (film)," the newest wave of U.S. Robotics robots is far more humanoid in facial expressions and appearance. This disturbs main character Det. Del Spooner, who was already bothered by the boxy metal robots that preceded them. "Why do you give them faces?" he asks one of the robots' programmers as he stares into a sea of identical new robots. He then discharges his firearm into the "face" of a robot at point-blank range, effectively making his point to the movie audience who will gasp at the sight of him "executing" a "person."

Uncanny Valley - Uncanny Valley as an analogy outside AI

In ESPN's "Page 2" feature[1], columnist Patrick Hruby explained Uncanny Valley in the traditional sense, noting that in Madden NFL 06 the players exhibit the unnervingly almost-human features that plague many CGI films. The column extended the Uncanny Valley term to the well-documented analogous debate over what sort of sports fan suffers more, one who roots for a perennial loser or one who roots for a perennial second-best. Hruby suggests that the perennial second-best fans, like the Red Sox Nation, suffer more because of the "Uncanny Valley" between the team's clear potential for perfection and their history of falling just short of the championship.

Adapted from the Wikipedia article "Uncanny Valley", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki