Man who sees upside down provides clues on how we process faces

Claudio, a 42-year-old whose head has been in an upside-down orientation since birth because of a medical condition, has provided us with new insights into the way the human brain processes faces. Unlike most people, he shows similar levels of accuracy when asked to identify faces in images regardless of whether they are shown upright or inverted. This suggests that the way we recognise faces is due to experiential as well as evolutionary factors.

Humans are typically much worse at processing information in faces that are presented upside down rather than right-side up. This phenomenon is known as the face inversion effect. “This affects almost every aspect of face perception – identity, reading people’s facial expressions, deciding whether somebody’s attractive,” says Brad Duchaine at Dartmouth College in New Hampshire.

Why humans are often better with upright faces than inverted ones is unclear. One theory suggests it is simply because we are exposed to more upright faces in our daily lives. Another is that our visual system has evolved to process faces with the same orientation as ours. To discern which theory is correct, Duchaine and his colleagues worked with Claudio and 22 people who typically hold their heads upright to test facial perception skills.

Claudio was born with a joint condition called arthrogryposis multiplex congenita, which restricts range of motion in multiple joints. As a result, fixed joints in his neck have caused his head to be permanently rotated backwards between his shoulder blades. Thus, most faces he encounters are held in a mismatched orientation to his. However, this has not negatively impacted his ability to read, write and navigate the world; he works as a tax accountant.

The researchers wanted to know if Claudio identifies upright faces better than inverted ones. If so, it would suggest facial perception is based on experience, given that most faces Claudio encounters are upright. If, however, Claudio identifies inverted faces most easily, it would offer evidence that facial perception skills arise from an evolved mechanism that allows us to better process faces in the same orientation as our own.

Their experiments showed that Claudio actually identifies faces with broadly similar levels of accuracy, regardless of their orientation. Study participants were asked to determine whether two images – one a side profile and one showing the full face – showed the same person. Claudio answered correctly 61 per cent of the time when shown upright faces and 68 per cent of the time with inverted ones. The control group’s accuracy was, on average, 83 per cent for upright faces and 64 per cent for inverted ones.

Claudio’s comparable accuracy with upright and inverted faces offers strong support for the idea that both evolutionary and experiential factors drive facial perception, the researchers conclude.

“There are a lot of people who have face processing deficits due to developmental factors,” says Duchaine. Many people with autism, for instance, struggle to process faces. Duchaine says that better understanding the mechanisms behind these skills may lead to new ways of reducing or treating impairments in facial processing.

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