Researchers are dipping further into the uncanny valley. Here’s what they think they found.

The uncanny valley is a persistent problem looming ever larger on game developers minds as games become more eerily life-like and titles like Heavy Rain, LA Noire, and Uncharted reach for bold cinematic visuals. A new research them led by Ayse Saygin, a cognitive scientist at the University of California, San Diego, is now trying to pinpoint what exactly makes us so nervous about these types of images, Mashable reports:

Saygin and fellow researchers don’t think the phenomenon follows the valley metaphor exactly. Instead, they suggest the uncanny valley sensation arises when an artificial figure looks or behaves real enough to trigger a mental switchover — the viewer’s brain suddenly begins to consider the figure as a possible human. The artificial figure almost inevitably fails such close inspection.

“Pixar took a lesson from Tin Toy,” said Thalia Wheatley, a psychologist at Dartmouth College. “We have to nail the human form or not even go there.”

Wheatley’s lab has found that everyone from Dartmouth college students to a remote tribe in Cambodia shows a strong sensitivity to what does or does not appear human. But such findings held up only when the researchers showed people human faces that were familiar to their ethnic group.

When shown a series of doll-like and human faces made with “morphing” software, people said a face was more human than doll only if it had at least a 65 percent mix of a human face. People could even judge an artificial figure’s human appearance based on seeing a single eye.

“Evolutionary history has tuned us to detect minor distortions that indicate disease, mental or physical problems,” Wheatley explained. “To go after a human-looking robot or avatar is to go up against millions of years of evolutionary history.”

So the fear doesn’t exactly come from the almost-human appearance failing, but rather stems from our internal process to immediately register that failure. But why exactly do we need to learn how to overcome the uncanny valley? With these kind of advances, argues robotics researcher at Indiana University Karl MacDorman, the ability to engage with players emotionally and have them empathize with the characters on-screen is severely limited: “We predict that uncanniness will interfere with participants’ normal empathetic response within this scenario. This will help us understand how the uncanny valley influences emotional empathy during an interaction.”

[via Mashable]