More than 20,000 people have contacted Brad Duchaine through his website, faceblind.org, with complaints of having trouble recognizing familiar faces. Duchaine, a professor and chair of the Department of Psychological and Brain Sciences, has helped to establish that as many as one in 50 people have some form of prosopagnosia, or face blindness.
Nell was the first to reach out with the opposite problem: everyone, even complete strangers, seemed familiar. Her case is the subject of a new study in the journal Cortex by Duchaine and researchers at the University of York exploring hyperfamiliarity for faces, a rare condition in which the brain generates an overwhelming—and false—sense of familiarity.
The 49-year-old British woman emailed Duchaine during the pandemic after returning from a trip to an unfamiliar seaside town where everyone she encountered in passing seemed familiar. “She remembers distinctly thinking it's nice that so many people from her hometown are here. And then she realized—no, that’s not possible,” says co-first author Mary Kieseler, who conducted the research as a Guarini PhD student in Duchaine’s Social Perception Lab and is now a postdoc at Switzerland’s University of Fribourg.
Nell—a pseudonym given by the researchers to protect her privacy—had experienced an unusual migraine a few weeks earlier, and just after, had mistakenly confused a stranger on a bicycle for her ex-boyfriend. She searched the internet for her symptoms, but when nothing came up, she began investigating face-processing abnormalities. That’s how she found Duchaine. The timing was fortuitous: his collaborators at York, not far from Nell’s home, were about to begin a brain imaging study comparing the neural patterns of Game of Thrones fans with those, like Nell, who had never seen the show, and knew nothing about its characters.
Earlier neural data had shown that Nell’s core face-processing regions were working normally, and prior experiments had confirmed that she could recognize celebrity faces and tell faces apart when images were presented side by side. “But if you show her just one face and ask her, is that person familiar? Have you seen them before? That’s when it became difficult,” says Kieseler.
In one experiment, Kieseler showed Nell photos of her friends and family—provided by Nell’s husband—interspersed with 100 unfamiliar AI-generated faces. “She had just shown me she could recognize faces fine,” says Kieseler. “But when asked to make a familiarity judgment, it was so hard that she literally classified a third of the AI-generated faces as personally familiar. That just wouldn't happen to anyone with intact face familiarity processing.”
During the brain imaging study, Nell and the other participants watched video clips inside an fMRI scanner as researchers tracked their brain activity. The brain scans revealed that Nell’s neural patterns more closely resembled those of viewers familiar with the characters from Game of Thrones. “We didn’t know what we would see, and it was just really surprising that the fMRI captured it,” says Kieseler.
The scan results helped explain why Nell’s sense of familiarity felt so indiscriminate. Her basic face and visual-processing regions responded similarly to the control participants, suggesting normal functioning. But they also showed heightened connectivity to the hippocampus and surrounding medial temporal lobe—just like the Game of Thrones fans.
“This suggests that the feeling of familiarity doesn’t come from visual regions alone, but from coordinated interaction between face-processing areas and medial temporal memory systems,” says Joe DeGutis, a cognitive neuroscientist at Harvard Medical School and the VA Boston Healthcare System who was not involved in the study. “In hyperfamiliarity, that interaction appears dysregulated, generating a false sense of familiarity.”
Intriguingly, this raises the question of whether some cases of face blindness, which can be seen as the opposite of hyperfamiliarity for faces, result from the medial temporal lobe receiving a weak familiarity signal.
“The neural abnormalities we found in Nell suggest that the opposite pattern of dysfunction within this pathway may contribute to conditions such as prosopagnosia, in which individuals fail to recognize when a face is familiar,” says Duchaine. “It’s a good example that even within a limited system like the face network, disruptions can result in a wide range of disorders.”
Nell’s hyperfamiliarity extends well beyond the people she passes on the street. License plate numbers and names she encounters in print feel familiar, too—an annoyance that led her to give up reading the newspaper.
While there is currently no treatment, the researchers were able to validate Nell’s experience with scientific evidence, “confirming that she's not making it up,” says Kieseler.
Duchaine says he suspects there may be more people out there, like Nell, who experience hyperfamiliarity with faces. “Individuals experiencing symptoms like Nell’s or who are having difficulty with processing faces are welcome to contact me and my team as we hope to do more research in this area,” he says.
As for the unnerving experience of mistaking strangers for people she knows, Nell has found ways to cope. “It can be hard to bear sometimes,” says Kieseler. “But she has decided to look on the bright side. ‘Everywhere I go I feel welcome,’ she says, ‘because I feel like I know everybody.’”