Researchers say a phenomenon known as Uncanny Valley is a real thing and here’s how our brain reacts to it.

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The theory on why humanlike robots make us feel uneasy was first proposed in 1970. Getty Images

Have you ever gotten an eerie, unsettled feeling when you’re watching a movie with computer-generated imagery of a face or when you see a video of a humanlike robot?

You might be experiencing Uncanny Valley, a physical reaction to the sensation of not quite humanness.

As technology has progressed, the idea of Uncanny Valley has progressed from scientific theory to mainstream pop culture knowledge.

However, researchers have not known much about what causes the phenomenon — until now.

The concept of the Uncanny Valley is the idea that as robots and other simulacra approach human-like features they appear more odd and creepy than those that are more obviously unhuman.

It was first proposed by Japanese roboticist Masahiro Mori in 1970.

Mori himself did not elaborate on his hypothesis, but others have taken up the torch since.

Most recently, a team of researchers from the University of Cambridge in the United Kingdom and the RWTH Aachen University in Germany have done so.

That group, publishing in the Journal of Neuroscience, believes they’ve traced the origins of the Uncanny Valley effect.

They say it’s in two different sections of the medial prefrontal cortex, a part of the brain that evaluates stimulus and also assesses risk and fear.

In a series of tests, participants were asked first to rate images of humans, robots, and robot-like humans in terms of likability and humanness.

They were then asked to rate which of these agents they would trust to select a personal gift for them.

Researchers found a clear preference for both the humans and the machinelike robots and the least preference for those almost, but not quite, human images.

In other words, Mori’s hypothesis bears out in the brain.

“We were surprised to see that the ventromedial prefrontal cortex responded to artificial agents precisely in the manner predicted by the Uncanny Valley hypothesis, with stronger responses to more human-like agents but then showing a dip in activity close to the human/non-human boundary — the characteristic ‘valley,’” said Fabian Grabenhorst, PhD, study co-author and a lecturer in the department of physiology, development, and neuroscience at the University of Cambridge.

The Uncanny Valley is named in part because it supposes a literal drop in the curve of likability between non-humanness and not quite humanness, rising back up in likability as we get close to human-looking.

But can we learn to love the robots, no matter how uncanny the might be? It’s hard to say.

One study from Frontiers in Psychology in 2015 showed that when people interacted with both a human-looking “uncanny” robot and a machinelike robot, the same links between likability and degree of uncanniness held true.

More intriguing, however, was the finding that when the machinelike robot behaved negatively, its likability was erased right down to the level of the negatively behaving humanlike robot.

Positive behavior by the humanlike robot, by contrast, did not increase its likability.

In other words, “the effect of a robot’s attitude is not independent of its embodiment,” the researchers wrote.

That could mean that the only possible solution to the valley is better-looking human facsimiles, whether that’s among robots or onscreen CGI.

One 2012 study from researchers at the University of North Carolina and Harvard University suggested that it’s not just appearances, however, but our perception of the experiences of these uncanny machines that makes them most unsettling.

“People may refer to their car as upset or their spouse as robotic, but this research — and many popular movies — suggest that when a car really is upset or a spouse really is a robot, it is unnerving,” they wrote.

Their experiments found that “feelings of uncanniness are tied to perceptions of experience, and also suggest that experience — but not agency — is seen as fundamental to humans, and fundamentally lacking in machines.”

On the other hand, maybe likability isn’t necessary and trust can be built between humans and humanlike machines.

“We know that valuation signals in these brain regions can be changed through social experience,” said researcher Astrid Rosenthal-von der Pütten, PhD, a professor in the department of society, technology, and human factors at RWTH Aachen University and a co-author of this latest Uncanny Valley study. “So, if you experience that an artificial agent makes the right choices for you — such as choosing the best gift— then your ventromedial prefrontal cortex might respond more favorably to this new social partner.”

The study also indicated that reactions to the Uncanny Valley aren’t one size fits all.

“This is the first study to show individual differences in the strength of the Uncanny Valley effect, meaning that some individuals react overly and others less sensitively to human-like artificial agents,” Rosenthal-von der Pütten said in a press release. “This means there is no one robot design that fits — or scares — all users. In my view, smart robot behavior is of great importance because users will abandon robots that do not prove to be smart and useful.”