Some of the latest advancements in robotics are pretty impressive.

Just look at Atlas, a humanoid robot, built for the US defense department.

Atlas is remarkable because it's built to look and act like a person.

But sometimes, engineers get a little carried away.

They end up with a creation that drifts into a no-man's-land

Between something that's lifelike, and something that's actually alive.

This void is commonly referred to as "The Uncanny Valley"

Journeying into the valley often elicits an emotional response

somewhere between uncomfortable and creeped out.

Japanese robotics professor, Masahiro Mori coined the phrase way back in 1970.

He noted a positive reaction toward a human-like robot

can quickly turn to disgust.

Mori thought this response was triggered by subtle imperfections

in the robots appearance.

Another hypothesis has to do with our expectations

of how people and robots are supposed to look and act.

Atlas for example, clearly looks like a robot.

You'd have no problem leaving him in your garage overnight.

Animation also provides us with some examples of the Uncanny Valley effect.

Movies like The Polar Express and Beowolf

were widely panned, because their characters ventured into Uncanny territory.

It's especially difficult for roboticists

and animators to render lifelike hair eyes and skin-tone.

It's even harder when you introduce motion.

New technologies promise to bridge the gap between the lifelike and the living.

But they're trying to hit a moving target.

The Uncanny Valley begins and ends in different places for different people.

And besides, we like to think that humans can't be replicated.

For Scientific American's Instant Egghead I'm Larry Greenemeier.