University of Tübingen: Facial expression recognition proves that the brain is still superior to the computer

Our brain processes facial expressions regardless of the shape of the face – this is how we even understand the emotions of fantasy characters like Master Yoda
Faces of a human and a monkey avatar, each with a typical expression of emotion
Photo-realistic human and ape avatar, whose facial movements varied between human and ape-typical expressions of anger and fear.
We are currently aware of the corona mask requirement: Facial expressions are one of our most important communication signals. We make surprisingly few mistakes when interpreting facial expressions, even if the person we are talking to is not human. So we immediately recognize that Master Yoda is skeptical – even if we are not die-hard Star Wars fans and see him for the first time. Humans are still far superior to artificial intelligence (AI), which can recognize human faces very well, but fails miserably with fantasy figures if they have not been trained on it beforehand.

Professor Dr. Martin Giese and Professor Dr. Peter Thier from the Hertie Institute for Clinical Brain Research and the Center for Integrative Neuroscience at the University of Tübingen now have a possible explanation for why our visual system is superior here: the shape of the head does not seem to play a role for people in the perception of facial expressions. In contrast, AI systems have problems recognizing facial expressions on face shapes that differ greatly from those previously trained. Current facial recognition programs, such as those used in security systems or in forensics, can therefore not easily read Master Yoda’s facial expressions. The reason our brain is so good at interpreting facial impressions may be because of our evolutionary history,

For their study, the Tübingen scientists created three-dimensional computer-animated faces of people and monkeys. “We used methods that were also used in Hollywood films such as ‘Avatar’ or ‘Lord of the Rings’,” says Nick Taubert, first author of the study. The researchers were able to control the movement of the facial avatars, which corresponded to the facial expressions typical of humans and monkeys when expressing “fear” and “anger”. The highlight: the monkey avatar could also adopt human facial expressions and the human avatar could show animal facial expressions.

During the experiment, human test subjects had to classify the facial expressions they perceived. The result: “The facial expressions were recognized equally well on both face avatars. Our test subjects immediately identified the human facial expressions on the monkey’s face, ”explains Michael Stettler, who carried out the experiments. “They learned the monkey expressions, which are very different from the human ones, after a few repetitions.” The different facial shapes of the human and monkey avatars therefore seem to play no role in recognizing the emotional expressions.

The research team suspects the reason for this result to be the evolutionary development of our brain. “The anatomy of the facial muscles has changed very little in the last 25 million years, so that monkeys and humans can in principle perform very similar facial movements,” explains Giese, the head of the study. “The shape of the human head, on the other hand, differs significantly from that of the monkey; Our brain could have adapted to this difference and therefore process facial expressions regardless of the shape of the head. ”

The research team wants to further investigate which calculations the brain performs when recognizing facial expressions. “As soon as we have explained how facial expressions are processed regardless of the shape of the head, we could teach the AI ​​to understand Master Yoda’s facial expressions – even without extensive training,” says Giese.

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