LOS ANGELES - An increasing number of robots are being created and designed to work side by side with humans, in a human environment. That means robots have to be structured like a person, because some of them have to walk and sit like a person. Some robots are even being designed to look human.

But seeing an android, a robot that looks human, can make some people uneasy. That growing unsettling feeling or phenomenon as robots begin to look more like human beings is called the "uncanny valley."

Even researchers who work on robots are not immune to it.

“I know how they work. I know they’re just machines, but something about something that looks like a person but doesn’t quite move like a person is disturbing,” said Jonathan Gratch, director for virtual human research at the University of Southern California’s (USC) Institute for Creative Technologies.

Gratch, who is a research professor of computer science and psychology, studies human-computer interaction.

He said there are many thoughts behind why the uncanny valley exists. One explanation is that it’s biological. People are hardwired to recognize when something seems wrong.

“In my research, I study emotion and how we use emotional cues to read each other’s minds, and I think a lot of the issue for me is if you try to make something very realistic, then you start trying to read all this information into what it’s portraying, and it is not the right information. So, it just communicates something is off. Something is wrong with this interaction,” Gratch said.

Another theory is that a robot that looks too human threatens what it means to be human.

In this Sept. 28, 2017, photo, a robot head is cov In this Sept. 28, 2017, photo, a robot head is covered by Hanson Robotics' skin, in Hong Kong. In this Sept. 28, 2017, photo, a robot head is covered by Hanson Robotics' skin, in Hong Kong.

“Initially, humans were seen as the only intelligent entity. And now, we know more and more that animals can do many of the things that we do, build tools. We know machines are starting to become intelligent. We hold on to the fact that we’re emotional, but now these machines are starting to be emotional as well, which is perhaps a threat. So, where does that lead people?” Gratch explained.

A person’s religious beliefs and culture may also play into how an android is perceived, he suggested.

“In the Western tradition, coming from Christianity, humans are unique, perhaps uniquely possessing a soul. Whereas in Japanese Shinto culture, souls live everywhere, in rocks and machines,” Gratch said.

John Rebula is a postdoctoral fellow at USC and is working on making a humanoid robot walk like a person by being more coordinated and balanced. Applications include the ability to walk up a flight of stairs and sit in a chair made for a person. He said the robot’s face is not necessary and is clearly cosmetic.

“We really do think of these as research machines that we’re ripping apart and putting back together, ripping apart and putting back together. And so, it’s very easy for us to leave off the cosmetic bits," Rebula said.

His robot does have cartoon-like eyes, ears and a nose. It could be considered cute. However, if it looked more human, Rebula said he would not necessarily want to be in the lab with it all the time.

“We have lots of late nights in labs. You start yelling at the robot a little bit as it is — 'Oh, why aren’t you working?' I don’t necessarily, myself, need that extra layer of weird,” Rebula said.

People who design machines to work with humans do keep the uncanny valley in mind as they think about the look of a robot, and how widely it will be accepted by humans.