Why are robots and corpses so creepy? Welcome to the Uncanny Valley

Why do certain masks, mannequins, and robots have an unnerving appearance? Why do some clowns, corpses, and computer-generated cartoon characters give us the willies? It’s like they’re almost real—nearly human—but they’re just not right.

There’s something unsettling in their human-like but lifeless, soulless eyes. Or it could be their voices, which may be clear and even pleasing, but are somehow unnatural. Or maybe it’s something in their purposeful, articulated movement that’s just a little…off.

It’s called the Uncanny Valley effect, a theory presented in 1970 by Japanese roboticist Masahiro Mori. He postulated that the more closely a robot approximates human features, the more endearing it becomes…until it reaches a point when the subtle imperfections of appearance or behavior create an opposite effect—a sensation of eeriness and revulsion.

In the area between what is human-like and what is inhuman-like, there lies the Uncanny Valley.

Theories of the Uncanny Valley

Both the scientific community and mass media have grasped onto the Uncanny Valley effect and now take it as a given, but the reasons for the effect are still unknown. Here are just a few of the numerous hypotheses that aim to explain it:

• Cognitive dissonance: When we see a humanoid robot or a computer-generated video-game character that appears life-like but not altogether real, it causes a cognitive conflict—a feeling of both familiarity and discomfort. That is, the robot or computer-generated character may have many human characteristics, but it also has other characteristics that are distinctly non-human. Our brains experience tension because this entity fits into two conflicting mental classifications simultaneously.
  
  
• Pathogen/danger avoidance: This hypothesis suggests that humans have an innate, self-protecting feeling of revulsion to things that may be diseased or dangerous. A zombie, robot, or other animated being that moves similarly—but not similarly enough—to a human suggests a defect. The cognitive mechanism interprets this defect as disease or death, and provokes us to turn away from it in disgust.
  
  
• Mortality salience: According to this hypothesis, the Uncanny Valley is a reminder of one’s own death. “A dead person’s face may indeed be uncanny: it loses color and animation with no blinking,” Masahiro Mori wrote, adding that a “troubled” dead person’s face is even more uncanny. While dead things are creepy, dead things that can move are even creepier. Thus, this theory not only covers zombies (obviously), but also extends to robots and androids (and, undoubtedly, marionettes) by suggesting that we, like they, are animated only for the time being and will one day break down and be destroyed. (Mori also noted that dead people with a “quiet expression” are not so uncanny and uncomfortable but may appear “calm and peaceful.”)

Various researchers have suggested that these hypotheses are not exclusive of one another but may work together to produce the Uncanny Valley effect.

The eyes have it

The eyes are the window to the soul. But without a soul, the eyes are lifeless—even spooky. That’s the gist of a paper that showed how the eyes play a big part in the Uncanny Valley effect.

“Horror movies have discovered an easy recipe for making people creepy: alter their eyes,” wrote the authors in an article in Interaction Studies. “Instead of normal eyes, zombies’ eyes are vacantly white, vampires’ eyes glow with the color of blood, and those possessed by demons are cavernously black.”

To test this, these researchers performed an experiment in which participants looked at three different photos of the same man: the man’s nose was digitally erased in one photo, his eyes were erased in another photo, and the third photo was unaltered. Participants overwhelmingly chose the photo lacking eyes as the most uncanny.

So, if you really want to scare the trick-or-treaters in your neighborhood this Halloween, take a trip to the Uncanny Valley to select a costume that covers or otherwise affects your eyes.