This brain region may be why some robots send chills down your spine

The ‘uncanny valley’ effect is an unsettled sensation caused by bots that are too humanlike


CREEPY FEELING  By gauging people’s reactions to pictures of robots that looked more or less humanlike (examples above in this composite image), researchers uncovered a region of the brain that may be responsible for the “uncanny valley” effect.

A.M. Rosenthal-vonder Pütten et al/J. Neuroscience 2019

A new analysis of brain scans may explain why hyperrealistic androids and animated characters can be creepy.

By measuring people’s neural activity as they viewed pictures of humans and robots, researchers identified a region of the brain that seems to underlie the “uncanny valley” effect — the unsettling sensation sometimes caused by robots or animations that look almost, but not quite, human (SN Online: 11/22/13). Better understanding the neural circuitry that causes this feeling may help designers create less unnerving androids.

In research described online July 1 in the Journal of Neuroscience, neuroscientist Fabian Grabenhorst and colleagues took functional MRI scans of 21 volunteers during two activities. In each activity, participants viewed pictures of humans, humanoid robots of varying realism and — to simulate the appearance of hyperrealistic robots — “artificial humans,” pictures of people whose features were slightly distorted through plastic surgery and photo editing.

In the first activity, participants rated each picture on likability and how humanlike the figures appeared. Next, participants chose between pairs of these pictures, based on which subject they would rather receive a gift from. In line with the uncanny valley effect, participants generally rated more humanlike candidates as more likable, but this trend broke down for artificial humans — the most humanlike of the nonhuman options. A similar uncanny valley trend emerged in participants’ judgments about which figures were more trustworthy gift-givers.

Brain scans revealed that activity in the ventromedial prefrontal cortex, or VMPFC — a region involved in making value judgments — mirrored participants’ uncanny valley reactions. VMPFC activity was typically higher in response to more humanlike pictures, but dipped in response to artificial humans. That drop was most pronounced in people with the strongest dislike for artificial humans. Those findings suggest that this region of the brain underpins the uncanny valley sensation, the researchers say.

But this analysis may not directly map uncanny valley chills to neural activity, says human-computer interaction researcher Karl MacDorman. That’s because a lack of likability and gift-giving reliability don’t necessarily make something eerie.

Disney villains, for example, may not look particularly likable or trustworthy, but they don’t necessarily fall into the uncanny valley, says MacDorman, of Indiana University in Indianapolis. A future study could investigate the relationship between brain activity and how weirded-out people feel when they see different humanoids, rather than how much they like or dislike these figures.

If the VMPFC is responsible for generating the uncanny valley heebie-jeebies, that may be good news for android designers and animators. Social experiences can change how VMPFC reacts to certain situations, says Grabenhorst, of the University of Cambridge. So positive interactions with an initially creepy robot or avatar may make it less bothersome.

Previously the staff writer for physical sciences at Science News, Maria Temming is the assistant managing editor at Science News Explores. She has bachelor's degrees in physics and English, and a master's in science writing.

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