How do you feel about animatronic hands? What about Big Dog, the four-legged robot developed by Boston Dynamics? What are your thoughts on marionettes?

If you’re like most people, all three of these things cause some uneasiness to bubble up in your stomach. It’s not quite a curdling feeling so much as a strong discomfort. Maybe you’d describe it as a “revulsion.” The feeling is normal, and since 1970 this collection of nearly alive, sort-of-human things has fallen into a gray area known as the “uncanny valley,” and researchers want to understand why it’s so off-putting.

A Brief Stroll Through The Valley

In 1970, Japanese robot designer Masahiro Mori designed a graph that would come to lay the foundation for all uncanny valley research. On the x-axis he tracked human likeness, from zero to 100 percent. On the y-axis he charted familiarity, which may be better understood as comfort, or acceptance. Mori drew two lines, one for moving figures and one for those that stay still.

Near the origin, where things are hardly human and don’t invoke any sort of reaction, are industrial robots — mechanical arms that fold wrappers around bars of chocolate or put caps on tennis ball cans. Moving to the right, the graph slopes upward. The more humanlike something is, the more familiar we are with it. Stuffed animals and humanoid robots occupy roughly the same space around the halfway point.

But then something happens. Three-quarters of the way toward 100-percent human, the graph plummets. It falls down and down, sailing past the x-axis into the negative. On the still graph we’re surrounded by corpses, and a little while later, prosthetic hands. On the moving side of things, which Mori claimed had an amplified effect, we see zombies and robots. (Wave hello to Big Dog.)

Traveling further to the right, both graphs eventually stick their heads above water and resume their upward trajectory as sharply as they plunged in. Finally, and happily, we arrive at 100-percent human — the warm bodies of you and me — where we feel at home.

All We Are Is Animals

That dip below the x-axis is what Mori called the uncanny valley, and it’s what researchers like Karl F. MacDorman, from the University of Indiana, have come to spend entire portions of their careers studying. For MacDorman, the uncanny valley is an untapped well of insights into human biology, psychology, and, as his current research suggests, personality.

“In terms of biological mechanisms, avoiding dead bodies as a potential disease vector is very important,” MacDorman told Medical Daily. “And I think that’s part of the story with the uncanny valley.”

Deep in our lizard brains, where the hardwiring is kept locked up by evolution, we carry the instinct to avoid things that may cause us harm, even if that thing is projected onto a movie screen or plugged into a wall socket. Most of the time we do a good job of keeping our biological distance. If anything, we’ve come to admire zombies in popular culture. They can actually be endearing, in their own undead sort of way.

The more frightening issue, especially in today’s world where the singularity always seems to be right around the corner, is robotics. We’re afraid of being overthrown — of creating a master race of robots that are at once sentient, intelligent, and unstoppable. They are also immortal — assuming you can’t find the off-switch — which MacDorman says is a problem for our laggard brains because it reminds us we have expiration dates.

Psychologists refer to these brief flashes of mortality as “animal reminders.” They’re reality checks, MacDorman says. Severed hands in formaldehyde jars and walking through cemeteries are creepy because they force us to confront death. “We have a life span,” he said. “We’re born, we die — just like any other animals.”

The Trouble With Dropping A Pin

Not everyone responds the same to the uncanny valley; some are hardly fazed by it, in fact. MacDorman’s latest research sought to understand who, exactly, was most susceptible. In a study to be published sometime next year, he and Steven Entezari, a colleague from the University of Indiana, found uncanny valley sensitivity was greatest among those with religious fundamentalist beliefs, neuroticism, high sensitivity to animal reminders, and those with anxiety issues.

The last three seemed to fit the traditional understanding of uncanny valley sensitivity, but the first needed some thought. Ultimately, MacDorman chalked up the finding to an allegiance to creation, as the religious subjects in his study were all self-reported Christians. In line with the Christian belief humans are distinct from robots and other animals, an unclear middle ground wouldn’t be possible. Androids would upset, not intrigue, a religious fundamentalist.

MacDorman even goes so far as to use the theory as an explanation for the controversy of abortion. Personhood, he says, isn’t easily defined by conventional terms. We gained it somewhere in between being a fertilized egg and being the living breathing humans we are today. But trying to drop a pin on the exact point is impossible, and the effort we extend anyway could be causing us grief.

“It’s disturbing because it’s about us,” MacDorman said, referring to the difference between talking about human babies versus, say, a discussion on veal. “It could be the same reason why these android characters are disturbing, because really, one of the end points of the goal is to reproduce us. And if we were reproduced by machines, where does that leave our feeling of being special and human?”

Stopping Anti-Science

Watching a three-minute long video of a robot “dog” negotiate a pile of cinderblocks is pretty unnerving. We aren’t used to seeing dogs without faces or fur or tails perform the same actions as our eager-eyed best friend. And so our brain goes a little haywire, like when it sees an optical illusion. It tries to make sense of something that seems otherworldly, but at the same time familiar.

This MacDorman knows for sure. But as he points out, after having spent long stretches of time studying the uncanny valley in Japan, where Masahiro Mori first developed the theory, one begins to realize the valley is a bit wider — a bit deeper — here in the States. And it isn’t necessarily our belief in the divine, he says. It’s our general attitude toward science.

“In our culture, there certainly is resistance to things like stem cell research,” he said. “And things that aren’t such a big issue in other countries will be a big issue.” That’s not to say you should feel OK petting Big Dog, but at least give the technology another chance. Robotic dogs need love, too.