Spot of bother
A few studies have asserted that the whole thing doesn’t exist. In one study, David Hanson of Hanson Robotics, in Plano, Texas, and his colleagues showed participants images of two different robots that were animated to simulate human-like facial expressions. The survey simply asked the participants what they thought of the experience. The vast majority (73%) liked the human-like robots. In fact, not one person stated that these robots disturbed them.
Hanson and his team then showed the participants a continuum of images, starting with a picture of Princess Jasmine taken from the Disney movie Aladdin. Over the course of six images, Jasmine’s face slowly morphed into that of actress Jennifer Love Hewitt. The idea of these facial progression studies is to try to observe the dip in likeability that Mori predicted between an obviously cartoon image and an obviously human one. The participants were asked to rank the acceptability of each picture in the series. But, again, rather than see a dip in the scores in the middle of the range – as the uncanny valley would predict – none of the images seemed to bother anyone.
Why this happened isn’t clear, and not everyone thinks Hanson’s experiment is robust. Many other studies have shown the opposite. For example, Edward Schneider’s lab at SUNY Potsdam in New York collected 75 existing characters from video games and animation, including Hello Kitty, Mickey Mouse, Snoopy and Lara Croft. They asked participants how human and how attractive (or repulsive) they perceived each character to be. In this case, the researchers did find a dip in likeability in the middle of the series, roughly where the ogres from World of Warcraft sit.
Moreover, a team lead by Karl MacDorman at Indiana University conducted an experiment similar to Hanson’s, using a progression of images in which a robot face slowly morphs into a human one. They, too, found a U-shaped dip in likeability in the middle of their 11-image series.
However, among the labs that have observed the uncanny valley, there is strong debate about its shape. Christoph Bartneck, a robotics researcher at Canterbury University in New Zealand says that, based on his studies, a valley might be the wrong geological metaphor altogether. "As far as we can tell,” he says, "it looks more like a cliff." Essentially, he says, at the point where robots achieve extreme human-likeness, but remain discernibly un-human, their likeability plummets. And people only start to like them again when they become so human-like that they escape detection.
To make things even more complicated, there’s nothing that proves the uncanny valley reflects gradations of the same reaction. It could be a handful of reactions to different aspects of having a varying degree of human-likeness. When MacDorman showed his subjects videos of many different robots, the responses followed no clear pattern. "The results do not indicate a single uncanny valley for a particular range of human-likeness," MacDorman’s wrote in the paper. "Rather, they suggest that human-likeness is only one of perhaps many factors influencing the extent to which a robot is perceived as being strange, familiar, or eerie."
Questions about what reaction (or reactions) cause the uncanny valley (or, indeed, the uncanny cliff) quickly lead to other questions about why we react at all.
There are a few explanations that might account for our strange aversion to humanoid robots. One is that not being able to tell whether something is human or not can be a deeply unsettling feeling in itself. Artists and directors take advantage of this all the time for dramatic effect. The dread that viewers feel while trying to figure out who is a zombie, or Cylon, or alien might be the very same dread they feel when faced with a very realistic robot.