"If I tell you to close your eyes and picture a beach, can you do it?" This is probably the most unexpected of all the weird questions my friend Sam has asked me over the last ten years we've been mates. "My brother's just told me that most people can. But we can't," she explains, in response to my bemusement.
At 26, Sam has discovered that she's one of an estimated 2 per cent of the population affected by a condition called aphantasia, meaning that their mind's eye is effectively blind.
"When my brother first asked me if I could actually see the blue sea and picture the yellow sand, it seemed like a ridiculous question," she explains. "He'd been reading a news article about aphantasia, and said that most people can actually form some sort of image in their head. But I couldn't—it was just black."
At first, she adds, "I thought it might just be that people interpret it in different ways, but then I spoke to a few people and what they described was definitely nothing like what I experienced. I felt a bit gutted, like I'd just found out everyone has an amazing super power they've been keeping secret from me."
The term aphantasia has only been around since 2015, when it was coined by Adam Zeman, a professor of cognitive and behavioral neurology at the University of Exeter in the UK. Since then, Professor Zeman has heard from 10,000 people who, like Sam, are unable to visualize mental images.
Weirdly, the researcher first became aware of the condition ten years ago, through a patient who had lost the ability to use his mind's eye in his mid 60s after an operation on his heart. "He was a very articulate, intelligent man, and he'd previously enjoyed imagining the faces of friends and places he'd been; he used to read a lot and enjoyed entering the visual world conjured by the novel," Zeman explains.
"It wasn't absolutely clear what happened during his heart procedure, but we thought he'd probably had a minor stroke. When this happened, he became unable to summon imagery voluntarily."
It was only after this case was covered in Discover magazine that people started contacting Zeman to say, "I'm just like this guy, but I always have been." Many of them, like Sam, had spent their lives assuming that what went on in their own heads was the same as everyone else's.
Thirty-two-year-old Tamarafirst found out she was aphantasic at the age of 23 while shopping for a couch with her mother. "My mother's a strong mental imager and had seen the blueprints for my new room. When I said I liked this one couch, she just glanced at it and said, 'Nope, that won't fit.' When I pulled out the measuring tape, lo and behold it was too big," she explains.
"I asked her how she'd known, and she said she'd taken the couch in her mind and slotted it into the blueprint space. I felt bewildered, and I've never stopped questioning people about it ever since."
After discovering that she lacked her mother's ability to visualize, Tamara asked 463 different people if they could form mental images. "None were aphantasic, and each one saw mental images in a different way, at different strengths, and used them for different things," she says.
So what actually causes this mental quirk? As a neurologist, Professor Zeman says, "It's a very good question—but my hunch is that there is something a bit different about [aphantisic people's] brains, and that there may be a genetic component. For some people, aphantasia's a lifelong congenital condition; for others, you can arrive there if something bad happens to your brain or, I think, for psychological reasons."
When I try to picture images, I might see some flashes of light, but nothing voluntary.
However, Zeman points out, the research still has a long way to go. "Everything I've told you so far is based on subjective report and questionnaire data. We're just beginning to try and measure things like autobiographical memory, and put people in scanners to see if their brains behave differently when they try to visualize," he explains.
PhD student Tamara became so fascinated by her condition that earlier this year she gave a TEDx talk on "Seeing the world without a mind's eye."
"I'm fully aphantasic, including sight, smell, taste and sound, unlike others who have low levels of imagery and do dream in images," she explains. "I found that so interesting, how each one of us has a different capacity for mental imagery, even though each person assumes that everyone else visualizes in the same way as them."
Online resources like Tamara's TEDx video have also helped Sam put her own experience into words. "When I try to picture images, I might see some flashes of light, but nothing voluntary. It's like I'm interpreting the brain signals rather than processing them into an image, skipping out a stage but the end result is the same," she says.
"I know confidently what a loaf of bread looks, feels, tastes and smells like, and that if I were to see a loaf of bread I would be able to identify it as bread, but it's verbal information rather than sensory," she explains. "Or if I think of a friend, I know what they look like, I just can't see an image of them in my head. It feels as if they're standing in front of me in the dark—it's pitch black, I can't see a thing, but I know 100 percent that they're there."
For Zoe, who's 31, it was another online post, shared on Facebook by Firefox founder Blake Ross, that first got her thinking about mental images. "I'd spent 30 years of my life assuming that when people said 'that's a horrible mental image' or 'picture this,' that they were talking in metaphors," she explains.
Unlike Sam and Tamara though, Zoe isn't fully aphantasic. When it comes to the classic beach example, she says: "I have a very limited capacity for forming a mental image, but if I concentrate hard enough, I can call up a picture of a beach. It's blurry with washed-out colours like a bad photograph, and it's very generic."
It seems like magic that people can close their eyes and see image—I'd do it all the time if I could.
And, while both Sam and Tamara have trouble calling any of their senses to mind, Zoe says: "I can feel the sand between my toes and the warmth of the late afternoon sun on my skin. I can hear the gentle, rhythmic rush of the waves lapping the beach. I can smell the salty air and the tang of sun lotion. It's like I've just closed my eyes in a moment. That's far more useful to me than trying to make a picture."
According to Professor Zeman, this is pretty normal. "There's certainly a spectrum, and it varies according to whether it's just vision that's affected or whether all senses are affected," he explains. "If you give a large group of people a vividness questionnaire, you get a sort of bell-shaped curve of vividness reports. People with true aphantasia—like your friend who doesn't see anything—they're off that scale, so they're a bit special."
For Sam though, the discovery of her aphantasia has been a source of real frustration. "It seems like magic that people can close their eyes and see image—I'd do it all the time if I could," she says. "One person I spoke to said he could picture his mum as if she were standing in front of him, with his eyes open. Maybe I'm completely overestimating how other people see things, but compared to what people have described, [aphantasia] sucks."