We’re all getting used to face masks, either wearing them or figuring out who we’re looking at. They can even trip up those of us who are experts in faces.
“Actually, I just had an experience today,” said Marlene Behrmann, a cognitive neuroscientist at Carnegie Mellon University who has spent decades studying the science of facial recognition.
She went to meet a colleague outside the hospital where they collaborate, and didn’t realize the person was sitting right in front of her, wearing a mask. In fairness, “She’s cut her hair very short,” Dr. Behrmann said.
Scientists have some ideas about why masks make recognizing others’ faces difficult, based on studying the brains of average people, as well as people who struggle to recognize anyone at all. But even when everyone around us is incognito, we still have ways to find each other.
“We use face recognition in every aspect of our social interaction,” said Erez Freud, a psychologist with the Centre for Vision Research at York University in Toronto. In the faces of others, we find clues about their personality, gender and emotions. “This is something very fundamental to our perception. And suddenly, faces do not look the same,” Dr. Freud said.
That’s why Dr. Freud and co-authors decided to study how masks impair people’s facial recognition skills. They recruited nearly 500 adults to complete a common face memory task online. Participants viewed unfamiliar faces and then tried to recognize them under increasingly difficult conditions. Half the participants saw faces with surgical-style masks covering their mouths and noses.
People scored substantially worse on the test when faces were masked. The authors posted their findings, which have not yet completed peer review, online last month.
Authors at the University of Stirling in Scotland posted a similar study in June that also has not yet been through peer review. In that study, 138 adults completed online face-matching tests. When the scientists superimposed masks onto the faces, people performed worse — even when the faces belonged to familiar celebrities.
In Dr. Freud’s study, 13 percent of participants struggled so much to recognize masked faces that they may as well have suffered from prosopagnosia, or face blindness. Without masks, only 3.5 percent scored that low.
In the general population, prosopagnosia may affect about one in 50 people. Some have face blindness their whole lives; others develop it suddenly after trauma to the brain.
Just because you’re tripped up by face masks doesn’t mean you have true face blindness. Still, “People have got a little sense of what it means to be affected,” Dr. Behrmann said.
She added that for most adults, face recognition is an extremely sophisticated process that happens almost instantaneously. That’s especially true when we see people we know well. “Because it’s so good, it’s sometimes hard to get a window in to understand how it works,” she said. So scientists have gained much of their understanding of face recognition by studying people with prosopagnosia.
Other studies have tested people without face blindness. Researchers have challenged subjects’ powers of recognition by presenting faces upside-down, or faces entirely obscured except for one feature, or half-and-half creations of celebrities, such as George Clooney’s mouth and nose fused with Robin Williams’s eyes.
One of the main takeaways has been that facial recognition happens holistically, or all at once. We don’t scrutinize people’s features piecemeal. Rather, we take in the entire face in a glance. When half the face is hidden by a mask, the process suffers.
But all is not lost. Research has shown that out of all facial features, we rely most on the eyes to recognize people. Even if we struggle to know who we’re looking at when only their eyes are visible, we may still pick up information about a person’s identity and emotions. “A lot of information is conveyed by the eye region,” said Richard Cook, a psychologist at Birkbeck, University of London. “We’ve still got access to that information.”
“We also use other cues, and we can fall back on some of those other cues if they are helpful,” Dr. Behrmann said. For example, we might recognize people by the way they walk or talk, or by their facial hair or hairstyle (except for Dr. Behrmann’s recently trimmed colleague). Prosopagnosics may rely on these external cues already.
The observer’s culture may matter, too. In what researchers call the “head scarf effect,” study participants from Egypt and the United Arab Emirates, where women often cover their hair, outperformed British and American participants at identifying faces when only the eyes, nose and mouth were showing.
In some Asian countries, wearing masks in public to protect against viruses was commonplace before Covid-19. Might people in those parts of the world be more comfortable recognizing each other with their faces covered?
“It is indeed an interesting point,” said Katsumi Watanabe, a cognitive scientist at Waseda University in Tokyo.
There is a paucity of research directly addressing the question, but earlier studies have hinted at cultural differences in how people read emotions. “Western Caucasian people tend to decode facial expressions based on the mouth region, while Eastern Asian tend to use the information from the eye region,” Dr. Watanabe said.
That might make it easier for people in a country such as Japan to get used to interacting while masked, Dr. Watanabe speculated.
People who are very young today might experience negative long-term effects, though. Babies and toddlers who are surrounded by masks may not get the chance to fine-tune their holistic understanding of faces, Dr. Cook said. “If there is some sort of lasting effect, I think it’ll be seen in young kids that are growing up now.” He wonders whether their powers of facial recognition, like a second language learned later in life, might always carry a bit of an accent.
For now, Dr. Cook said, adults are having a hard time. In his work with other researchers who study prosopagnosics, “We’re hearing that people who do perform normally are struggling, and people who usually struggle are struggling even more.”
That also means a lot of people are newly appreciating their power of facial recognition, Dr. Cook said. “They’re realizing what it’s like to not be able to take it for granted.”