A century ago, psychologists identified "the
uncanny" as an experience that seems familiar yet foreign at the same
time, causing some sort of brain confusion and, ultimately, a feeling of fear
or repulsion. Originally no more than a scientific curiosity, this
psychological effect has gradually emerged as a profound problem in the fields
of robotics and computer animation.
The most familiar things in the world to us — the voices,
appearances and behavior of humans — are being replicated with increasing
veracity by animators and robotics engineers. Today's ultra-lifelike androids
and computer-rendered humans would seem to bridge the valley between the land
of the living and the distant cartoon world occupied by Disney princesses and
animé characters. But these characters aren't so much bridging the valley as
falling into it. When we look at them, they seem at once familiar and eerily
alien, triggering an uneasy feeling.
The spooky region occupied by these characters — so close to
us and yet so far — is known as "the uncanny valley." The term comes
from a graph created by Japanese roboticist Masahiro Mori that plots human
empathy against the anthropomorphism of robots. On the graph, as robots become
more realistic and we feel more and more empathy for them, the line trends
upward. But as the robots' humanism approaches that of actual humans, our
empathy for them — and the line on the graph — suddenly plummets. The
resemblance between human and robot goes from remarkable to repulsive, and this
precipitous drop became known as the "uncanny valley."
Karl MacDorman, a professor in the Computer-Human
Interaction Program at Indiana University, leads a research team that is
investigating why, psychologically, the uncanny valley exists. He hopes his
research will help animators and other roboticists bridge the valley by
creating human replicas that come across as lifelike and natural rather than
creepy. Doing so won't just improve animated movies and video games; androids
are becoming more widely used in everything from the service industry to iPhone
apps to scientific research. They're here to stay, so scientists are doing what
they can to make their presence more pleasant.
Mapping out the valley
Since 1970, when Mori first described the uncanny valley
effect in the context of robot/human interactions, scientists have been trying
to determine what it is about humanlike non-humans that creeps us out, exactly.
According to MacDorman, occupants of the uncanny valley have
one defining quality: "an eerie feeling elicited by a human character that
is highly realistic in some aspects but not others," he told Life's Little
Mysteries. For example, as MacDorman discovered in a recent study, "this
feeling can be elicited by a mechanical-looking robot that sounds human or a
human looking robot that sounds mechanical — or moves in a mechanical
way."
In other experiments, MacDorman's team showed that people
feel particularly disconcerted when characters have extremely realistic-looking
skin mixed with other traits that are not realistic, such as cartoon eyes.
Furthermore, in a 2009 study in which participants were asked to choose the
eeriest-looking human face from among a selection, the researchers found that
computer-rendered human faces with normal proportions but little detail were
rated eeriest. When the faces were extremely detailed, study participants were
repulsed by those that were highly disproportionate, with displaced eyes and
ears. In short, viewers seemed to want cartoonish facial proportions to match
cartoon-level detail, and realistic proportions to match realistic detail.
Mismatches are what seemed eerie.
Based on his research, MacDorman thinks the uncanny valley
effect happens when certain realistic traits lead us to expect all other traits
to be realistic as well; we feel disturbed and repulsed when our expectations
are then violated. Strangely, though, only human characters can trigger the
effect. In the highly successful computer-animated film "Avatar," for
example, "the uncanny valley was avoided by reserving computer rendering
primarily for the Na'vi characters and not the human characters,"
MacDorman said. The alien Na'vi in the 2010 film were humanoid and extremely
lifelike, but they were blue-skinned with other clearly non-human features, so
they didn't trigger the uncanny valley effect.
Creepy feeling
So why do we feel unnerved or repulsed by quasi-humans, but
not quasi-dogs or computer-rendered Na'vi? What's the evolutionary root of this
psychological phenomenon? There are several hypotheses, but as yet, no
scientific consensus. One is that the actions of androids and computer-rendered
humans might deviate subtly from how we expect humans to socialize and
interact, and as acutely social beings, we find the violations of our social
norms disturbing.
Alternatively, psychologist Christopher Ramey of the
University of Kansas suggests we struggle with the conceptual strangeness
presented by androids. "Humanlike robots may force one to confront one's
own being by creating intermediate conceptualizations that are neither human
nor robot," Ramey wrote in a 2005 article.
A third hypothesis is that "uncanny valley"
characters differ subtly from what we perceive as healthy and beautiful, and
that we reject them just as we reject mating with those we perceive to be
reproductively unfit. Along similar lines, other theorists have argued that we
feel disgusted by uncanny valley characters for the same evolutionary reason
that we feel disgusted by people with diseases. We sense that they are somehow
diseased, and steer clear in order to avoid contagion.
No one knows which of these guesses is correct. "I am
working on testing the various theories," MacDorman said.
Billion-dollar issue
Whatever the psychological root of the problem, there's a
lot to be gained from figuring out how to get around it. Many computer
animation studios, including industry leader Pixar, shy away from characters
that might get lost in the uncanny valley, preferring cartoon stylization
instead. They've watched braver studios fail. For example, ImageMovers Digital,
a computer animation firm headed by producer Robert Zemeckis, produced a series
of critical and commercial flops because of negative audience reactions to
their eerie characters.
MacDorman says it's easy to see why many of Zemeckis' CGI
(computer-generated imagery) films flopped — starting with "The Polar
Express" in 2004 and including "Beowulf," "A Christmas
Carol" and "Mars Needs Moms." "A common feature of
Zemeckis' films is a mismatch between the characters' physical appearance and
movement owing to the misuse of motion capture technology," MacDorman
said. (With motion capture, human actors are filmed and their motions are used
to animate digital characters.) "For example, in 'A Christmas Carol,' we
see an old man thrust into the heavens, and yet his movements are that of a
young acrobat. This mismatch between appearance and behavior breaks the
illusion of being transported into another world. Audiences lose their
identification with and empathy for the characters."
Ward Jenkins, an animator and blogger, has pointed out that
characters' eyes are often overly bright compared to the shadowy lighting of
scenes in Zemeckis' films, and that their eye/skin mismatch lands them in the
uncanny valley.
As Zemeckis has no doubt become acutely aware, you can't
make much money on a film whose uncanny protagonist doesn't garner empathy from
the audience. ImageMovers Digital closed in March after the failure of
"Mars Need Moms," though it announced in August that it would reopen
and continue trying to perfect the use of motion capture.
MacDorman says success will require matching the level of
realism of all aspects of the characters.
After all, according to MacDorman, there is much to be
gained from bridging the gap between the cartoon and the real world.
"Clearly, many topics demand a high degree of realism, of
authenticity," he said. "However, sometimes they also demand the
impossible of actors, such as extreme age progression and regression in 'The
Curious Case of Benjamin Button' or aerial acrobatics in 'The Matrix.'"
Those two films used computer animation in a way that did
not produce disturbing results, MacDorman said. This was partly because CGI was
used only when necessary, to animate actions that human actors could not
perform, and within this limited scope, great care was taken to give all
aspects of the characters the same level of realism. "Many viewers did not
realize that in 'The Matrix,' digital doubles of Keanu Reeves and Hugo Weaving were
used in some of the scenes," he said. "'The Curious Case of Benjamin
Button' was particularly adept at modeling and animating an elderly digital
double of Brad Pitt and compositing into actual film footage. This is a case
where we can say that the uncanny valley was bridged."
Follow Natalie Wolchover on Twitter @nattyover. Follow
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