Heather Sellers has prosopagnosia, more commonly known as face blindness. “I can’t remember any image of the human face. It’s simply not special to me,” she says. “I don’t process them like I do a car or a dog. It’s not a visual problem, it’s a perception problem.”
Heather knew from a young age that something was different about the way she navigated her world, but her condition wasn’t diagnosed until she was in her 30s. “I always knew something was wrong – it was impossible for me to trust my perceptions of the world. I was diagnosed as anxious. My parents thought I was crazy.”
The condition is estimated to affect around 2.5 per cent of the population, and it’s common for those who have it not to realise that anything is wrong. “In many ways it’s a subtle disorder,” says Heather. “It’s easy for your brain to compensate because there are so many other things you can use to identify a person: hair colour, gait or certain clothes. But meet that person out of context and it’s socially devastating.”
As a child, she was once separated from her mum at a grocery store. Store staff reunited the pair, but it was confusing for Heather, since she didn’t initially recognise her mother. “But I didn’t know that I wasn’t recognising her.”
Heather was 36 when she stumbled across the phrase face blindness in a psychology textbook. “When I saw those two words I knew instantly that was exactly what I had – that explained all the chaos.”
She found her way to Harvard neuroscientist Brad Duchaine who diagnosed her as having one of the three worst cases of the disorder that he had ever seen.
So what’s it like to not recognise anyone you know? Heather says the biggest difficulty with the disorder is recognising people who she is close to – the people that are most important to recognise. In the school where she teaches English she is fine, because she recognises people by their clothes or hair and asks her students to wear name badges.
But it can be harder in social settings. Once she went up to the wrong person at a party and put her arm around him thinking he was her partner. And at college men would phone her angry that she had walked straight past them after they had had a date. “At the time I was thinking ‘I didn’t see you, why is everyone making my life so difficult?'”
It’s not just other people Heather doesn’t recognise – she can’t identify her own face either. “A few times I have been in a crowded elevator with mirrors all around and a woman will move, and I will go to get out the way and then realise ‘oh that woman is me’.” She also finds it unsettling to see photos and not recognise herself in them.
To try and understand the condition, Duchaine and his colleagues recorded brain activity while 12 people with prosopagnosia looked at famous and non-famous faces. The team found that part of the brain responsible for stored visual memory was activated in six people when they saw the famous faces.
But another component of brain activity thought to represent a later stage of face processing wasn’t triggered. “Some part of their brain was recognising the face,” says Duchaine, but the brain was failing to pass this information into higher-level consciousness (Brain, doi.org/fzmqgz).
“There may be training where we give people feedback and say ‘look you recognise that face even though you’re not aware of it’,” says Duchaine.
Now Zaira Cattaneo at the University of Milano-Bicocca in Italy and colleagues have identified the specific brain areas that allow us to recognise our friends. The team used transcranial magnetic stimulation to block two vital aspects of face processing in people without prosopagnosia. Targeting the left prefrontal cortex blocked the ability to distinguish individual features like the nose and eyes, and blocking the right prefrontal cortex impaired the ability to distinguish the location of those features from one another (NeuroImage, doi.org/mff).
“We made performance worse,” says Cattaneo. “We want to make it better.” Now the team are trying to activate these areas of the brain. “The aim is to enhance face recognition abilities by directly modulating excitability in the prefrontal cortices,” says Cattaneo.
Would Heather want a cure, should one be found? “I can’t imagine what you see when you see a face, and it’s scary,” she says. “I go back and forth on what I’d do. I’ve done so much work in figuring out how to chart my world, I’d need to do a whole new rewrite. But it would be fascinating.”