Close your eyes. Picture a beach. You’re probably seeing the sunlight reflecting off gentle blue waves, the coarse sand stretching off into the distance, colorful towels and umbrellas, seagulls fighting each other for scraps. You could do the same with any number of scenes: your bedroom, a sunset, your parents’ faces. Each time, it’s like a photograph in your head. Or so I’ve been told.

I wouldn’t know. Because when I close my eyes and picture a beach, I see nothing.

I have aphantasia, which means I can’t form mental images—I lack a “mind’s eye.” Technically, I don’t have full-blown aphantasia—I can form brief snatches of images, but they’re dim and fleeting and can only encompass a small thing, like a single piece of furniture rather than a whole room. Some things I can’t picture at all: people’s faces, detailed color (like a sunset), movement. Even with the fleeting images, I’m not sure how much is really “seeing.” As Mozilla co-founder Blake Ross described in his essay on his recently-discovered aphantasia, it’s more like I’m seeing the “essence” of things.

You’d think this is something I’ve always known. To non-aphantasiacs, it probably seems like a glaring difference in how my brain works. But I actually didn’t realize until a year and a half ago, when I discovered a BBC article on aphantasia This was also the first time scientists had named and were studying the phenomenon. The article came with a sample “vividness of visual imagery” questionnaire used by researchers. The questionnaire asked respondents to picture things like a loved one’s face, gait, and clothes; a sunrise; an approaching thunderstorm. For each image, you could choose one of five options ranging from “no image at all” to “as vivid as real life.” I chose “vague and dim” or “no image at all” for every question.

Wait, I thought, there’s no way people are answering ‘as vivid as real life’ for any of these. So I asked two of my friends to take the quiz. One of them gave the two highest answers for every question. “How does that even work?!” I asked.

Non-aphantasiacs are astounded when they learn about aphantasia; for me, it was astounding to learn that people can see whole scenes, as vivid as real life, in their heads. Ross describes doing the same thing in his essay: upon learning of aphantasia, he messaged every friend online at that moment and asked them to picture a beach, amazed when they said it was like actually being there.

How had I never figured this out? It’s partly because my aphantasia isn’t 100%. I thought the vague, fleeting images I got were what people meant when they talked about “picturing” something. I took phrases like “mind’s eye” figuratively, not realizing that it was literally like having another eye.

It's also because aphantasia never interfered with my life. I can still, for example, describe all the knickknacks on top of my childhood dresser—I’m just not “seeing” the dresser in the process. (I can’t describe what I’m thinking of instead. This is one of the things that makes studying the brain difficult—no one else can understand what it’s like in your head. Which is another thing that kept me from realizing I was unusual.) And contrary to the way many articles about aphantasia describe it, I do have an imagination. I can think of elaborate future scenarios; I can recall past events in detail. That imagination just isn’t visual.

Some aphantasiacs say they also can’t hear songs in their head or smell familiar scents even when they’re not there. For my part, I can hear music in my head just fine, as well as different people’s voices. But I can’t fathom the idea of being able to conjure up a smell or taste.

After realizing I had aphantasia, and reading all the articles that came out in the wake of that initial BBC article, a number of things about me were explained. Any relaxation exercise that involves picturing a calming scene, like a garden, is a non-starter. I have a terrible memory for faces, since I can’t picture if I’ve seen that face before. Contrary to what is apparently the norm, I’m far better at remembering names. This is true even for short time spans; at the library where I work, I’ve learned to focus on a patron’s hair or clothing, so if they come back to ask for more help a half hour later, I won’t second-guess if they’re the same person from before. (Note that this is not the same as prosopagnosia—face blindness. I do recognize faces; it just takes me a few tries to remember new ones.) I often joke that I would be a terrible eyewitness to a crime. The sketch artist would ask me to describe the suspect’s eye color, nose size, face shape, and I would probably reply, “I don’t know…it was a typical face?”

I may have gotten a 5 on both AP Calculus exams, but I struggle doing math in my head when it involves multiple-digit numbers. I can’t picture the whole equation at once, carrying the units like I’m writing on a blackboard. I can only focus on snippets of it, and between all the carrying or borrowing, by the time I get to the hundreds place, I’ve lost track of what I put in the ones column.

Aphantasia also explains my longtime love of photography. Growing up I was constantly snapping away at family gatherings. Now I know why: if I didn’t capture the moment that way, I’d never be able to see it again.

I’m bored by long descriptive passages in books because the description doesn’t “paint a picture.” When I do get fragments of images, they can only be things I’ve seen before; I cannot picture an entirely new place. I’ve never experienced the common feeling of having a movie adaptation come out and being disappointed when the characters look nothing like you pictured them. In my case, it’s the opposite: one thing I like about movie adaptations is that I can finally see what the characters look like. I have the same pitfall when writing, and it helps explain why I’ve gravitated toward non-fiction in recent years.

What’s fascinating, though, is that I still dream. My dreams are colorful and detailed, and in them, I often go to made-up places. In my waking life, the closest I come to visualizing happens when I’m not trying. The more I make an effort to “focus” on an image, the dimmer it becomes. My brain is, on some level, capable of visualization, but there’s a disconnect on the way to my conscious thoughts.

None of this is shared to inspire pity. I certainly don’t consider aphantasia a disability, or even a disorder. It’s just an interesting way my brain works. And aphantasia does have its advantages. I only recently realized that, when most people see something disturbing and exclaim “I’ll never be able to unsee that,” they don’t just mean they won’t be able to stop thinking about it. They mean literally seeing.

Because it’s easy for me to unsee an image. It disappears as soon as I look away.