[News Terms] Uncomfortable, Human? ... The "Uncanny Valley"

The Uncanny Valley Where AI Affection Plummets
Hypothesis First Appears in Japanese Oil Company Promo
Study Shows Monkeys Also Experience the Uncanny Valley

“Loss of appetite makes it effective for dieting” vs “AI will become more familiar, so we look forward to the future!”

Recently, Japanese McDonald's posted a 16-second AI advertisement video on its official X (formerly Twitter) and other platforms, which received mixed reactions from netizens. The video, promoting a discount on French fries, features 11 AI female models. Among them, one model throwing French fries into the air was noticed to have six fingers, leading to comments about the “Uncanny Valley.”

McDonald's Commercial Video Using AI Model
Photo by X (formerly Twitter)

The “Uncanny Valley (不?味の谷·Uncanny Valley)” phenomenon is a hypothesis proposed in 1970 by Masahiro Mori, a Japanese roboticist and professor emeritus at Tokyo Institute of Technology. This phenomenon is explained through a graph where the vertical axis represents affinity and the horizontal axis represents similarity. As one moves away from the origin, both affinity and similarity increase. Humans tend to feel more favorable as robots resemble humans more closely. However, when affinity and similarity reach a certain level, affinity suddenly drops sharply, and humans experience strong repulsion. Mori named this area the “Uncanny Valley.” This explains why some viewers felt discomfort and disgust toward the McDonald's advertisement.

A common misconception in Korea is that the “Uncanny Valley” was first introduced by Professor Mori in an academic paper. In fact, it was first published in a promotional magazine by an oil company. In 1970, the essay titled “Uncanny Valley (不?味の谷)” appeared in “Energy,” Volume 7, Issue 4, a promotional magazine of Esso Standard Oil Company Japan (now ENEOS Corporation).

At the time, there was no suitable academic journal for publication, and the essay initially received no attention. Professor Mori himself said, “It lay dormant without any response for a long time, but starting in 2005, it began to be cited in the West.” Since then, it has attracted attention worldwide in various fields such as philosophy, psychology, design, and Hollywood films.

Professor Emeritus Mori Masahiro, Uncanny Valley Graph
[Photo source=Tokyo Institute of Technology, Robotics Society of Japan]

Few people know the origin of the discovery of the Uncanny Valley phenomenon, which contrasts with the term’s widespread recognition. The discovery is related to the development of prosthetic hands. The year 1970 was the time of the first AI boom. At that time, Professor Mori extended the “creepiness” he felt toward prosthetic hands resembling human hands to the entire human body, including the face. This is how the Uncanny Valley phenomenon was born.

Why does the Uncanny Valley phenomenon occur? Scientists from the UK and Germany claimed to have discovered the brain regions responsible for the feeling of the Uncanny Valley. A joint research team from the Department of Physiology at the University of Cambridge and the Human Technology Center at RWTH Aachen University announced in 2019 that they identified two areas in the medial prefrontal cortex activated when experiencing the Uncanny Valley phenomenon.

The medial prefrontal cortex is the brain region that evaluates all external stimuli. One part of the prefrontal cortex judges whether something is a human face or not. The more an object resembles a human, the more this area is activated. Another part is the brain region associated with feelings of affinity. This area also became more active as objects resembled humans, but when viewing android robots that looked very similar to humans, it was instead suppressed. The research team analyzed that these two areas are involved in the Uncanny Valley.

Research on Monkeys and the Uncanny Valley
[Photo by semanticscholar]

Research has shown that animals also experience the Uncanny Valley. A research team at Princeton University in the United States observed this phenomenon in monkeys. In fact, monkeys showed discomfort when confronted with images resembling themselves more than with unrealistic monkey images or real monkey images. This research was published in 2009 in the Proceedings of the National Academy of Sciences (PNAS) under the title “Monkey visual behavior falls into the uncanny valley.”