What makes realistic robots so creepy?

We tend to anthropomorphize objects and animals. That is, we project human characteristics like intelligence and emotion onto nonhuman things, especially if they exhibit some human traits. So, you'd think this would mean we would take to a humanlike android more readily than a metal mechanoid. We do apparently feel comfortable with robots that have increasingly human physical attributes up to a point, but once this point is passed, we are repulsed. This effect is called the uncanny valley.

The uncanny valley is a term coined by Masahiro Mori in 1970. To illustrate this idea, Mori created a graph with familiarity on the y-axis and human likeness on the x-axis and plotted our feeling of familiarity, or ability to identify, with various robotic forms or human representations. Industrial robots are near the origin, neither humanlike nor evoking a feeling of familiarity. Humanoid robots approach a peak, being both more familiar and humanlike. But after this peak, there is a sudden drop off into a valley (where things like corpses, zombies and prosthetic hands lie), and it rises again to a second peak as it approaches a living human. In his view, our comfort level increases as robots gain more human physical traits up to an as-yet-undefined point, at which the human traits suddenly render the robot unfamiliar and creepy. Both physical appearance and motion play a role, as unhumanlike motion can also throw something instantly into the valley.

Studies have borne out this idea -- and modified it a bit. Researchers Karl MacDorman, Robert Green, Chin-Chang Ho and Clinton Koch at the Indiana University School of Informatics used still images with the facial features and skin textures altered in various ways to garner participant responses. They found that eeriness levels were rated higher with faces that deviated from normal human proportions when the skin texture was realistic, but that backing off of the skin realism caused eeriness to decrease. These results seem to indicate that a mismatch between proportion and realistic detail might be a culprit.

A study by Ayse Pinar Saygin, Thierry Chaminade, Hiroshi Ishiguro, Jon Driver and Chris Frith used a moving robot (Repliee Q2, actually) to show that the uncanny valley effect might be caused by a disconnect between our expectations and reality in regard to the appearance and movement of an android. The researchers took functional magnetic resonance imaging (fMRIs) of participants as they viewed a series of videos of Repliee Q2, a mechanical-looking robot (the same android, but "skinned" to reveal its underlying parts), and a live human (in fact, the android's model), all performing the same actions. Participants' brains responded to the human and more mechanical looking robot very similarly. But when viewing the more humanlike android, different areas of the brain showed activity than in the other cases, and these areas had to do with connecting the visual cortex with parts of the brain that have to do with affecting and interpreting movement. It provides evidence that maybe the uncanny valley effect is triggered when something that looks mostly human moves in a non-human way (i.e., where appearance and movement do not match the way our brains think they should). Robots moving like we expect robots to move and humans moving like we expect humans to move, of course, do not creep us out.

One possible evolutionary reason for our revulsion to variances in the appearance and movement of an android is that any irregularity in a human form might indicate illness, and we may be hardwired to recoil to prevent the spread of disease. A certain otherness in another person might also trigger our aversion to people who we wouldn't deem as acceptable mating partners. But whatever the underlying biological reason, roboticists are looking for ways to keep their creations out of the valley.

Although it's the goal of some roboticists to make androids that are so humanlike in appearance and motion that they get past the uncanny valley, many are sidestepping the issue by making non-humanlike but very expressive robots. Leonardo is a cute and furry robot made in collaboration between MIT and Stan Winston Studios. He can exhibit various facial expressions, can recognize faces and is being tutored by humans to learn various skills. And researchers such as Heather Knight believe that the social capabilities of the robot may also be key to avoiding the uncanny valley.

There is a school of thought that robots could be made to appear, as well as communicate and interact socially, just enough like people to make us comfortable with them, but not so much that they truly appear human. The idea is to give robots enough features that will make us anthropomorphize them, such as the ability to give and respond to communication cues, to recognize people's emotional states and respond accordingly, and to exhibit personality and emotion (however artificial), among other things. The robots would have their own form, one designed for whatever work they were meant to do, and the disconnect between our expectations and their appearance wouldn't occur. Mori himself even stated in his 1970 article that designers should strive for the first peak in his graph, not the second, to avoid falling into the creepy area. Perhaps this approach would help robots to fit seamlessly into our lives without giving us the heebie-jeebies.

But others continue to strive for total human realism, like Ishiguro, who is among those who believe that androids can bridge the uncanny valley by increasing humanlike appearance and motion. Aside from their realistic hair and skin texture, his Repliee Q2 and Geminoid HI-1 were both also designed to perform common involuntary human micro-movements, like constant body shifting and blinking, as well as breathing, to appear more natural. And they utilize air actuators, with the help of an air compressor, to affect motion without emitting mechanical noises.

Culture may also play a part. In Japan, artificial forms are already more prevalent and accepted than they are in places like the U.S. There have even been a couple of synthetic pop stars (one animated, and one a computer-generated mashup of the features of her real band members). Perhaps the uncanny valley can be traversed in other parts of the world via the increasing prevalence of androids. Maybe we'll all just get used to them.

But this is not a phenomenon that only occurs with robots. It happens with other largely realistic renderings of the human form, such as animations. There were many reports of people finding the animated human characters in the movies "Final Fantasy: The Spirits Within" and "The Polar Express" as creepy or off-putting. Both films were touted for their breakthroughs in computer graphics (CG) photorealism. But the characters weren't real enough to transcend the valley.

We can try everything from decreased realism to full-on human mimicry to further experiment with what forms and functions we are most likely to accept from our robot and computer-generated brethren. We need to either traverse or flat out avoid the uncanny valley, because robots and computer graphics are with us for the long haul.