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Neuroscientists discover the part of the brain behind the uncanny valley effect

The reason we’re sometimes freaked out by CGI humans in movies is because of something called the “uncanny valley” effect. First identified in the 1970s by robotics professor Masahiro Mori, the uncanny valley refers to the way our reaction to humanoid robots or other artificial people can tip over into revulsion.

In a new piece of research, neuroscientists and psychologists in the U.K. and Germany have identified the exact part of the brain in which this phenomenon takes place. In an experiment, the researchers studied the brain patterns in 21 healthy individuals using fMRI (functional magnetic resonance imaging) technology to measure how active different regions of the brain are when people are experiencing the effect.

They started out by showing participants pictures of humans, artificial humans, android robots, humanoid robots and mechanoid robots, and asked them to rate them according to likability and resemblance to humans. The scientists then asked the participants which of the agents they would trust to select a gift humans would like. While this was going on, the participants’ brain activity was measured. It highlighted that two parts of the brain’s medial prefrontal cortex are important for the uncanny valley effect.

“Our study shows that human reactions to artificial social partners involve specific activity patterns in the brain’s reward system,” Fabian Grabenhorst, a professor in the Department of Physiology, Development and Neuroscience at the University of Cambridge, told Digital Trends. “Different parts of the human brain closely track how much an artificial agent resembles a human being, how much we like this artificial entity, and whether we would accept a personal gift from them.”

Astrid Rosenthal-von der Pütten, a professor at RWTH Aachen University said that the uncanny valley effect taps into an important evolutionary trait in humans. “We have brain areas that, from birth on, are able to encode faces,” she said. “With three months of age, children start to categorize faces and respond to more familiar faces more positively. When interacting with our environment, we [pay] special attention to other humans. Put simply, humans are much more important to us than objects — because their behavior tells us whether everything is okay or whether we are in a threatening situation. We are highly trained to interpret other humans behavior and that presumably makes us more sensitive to subtle oddities in their behavior.”

There’s still plenty that we don’t know about the uncanny valley effect — such as whether the neural response will alter as people experience increased social interactions with artificial agents. However, there’s also no denying that the uncanny valley effect is real.

If you thought you were the only one freaked out at the CGI characters in Robert Zemeckis’ 2004 movie The Polar Express, you can breathe a sigh of relief.

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