In 2013, I was four months into my job at The Washington Post when we had a going-away party for a woman who was moving to Philadelphia. Everyone gathered around my section’s little newsroom while our boss talked about Sara’s contribution to the paper, how sad we all were to see her leave.

I, personally, was neutral on the subject. I hadn’t gotten to know Sara, just as I hadn’t really connected with anyone in my new office, but I had noticed that she was unusually versatile. A news editor/fashion writer would be hard to replace.

“I think that as you get older, it gets harder to make friends with your co-workers,” I opined to my boyfriend, Steve, that evening.

When I got to work the next day, I was surprised to see Sara there, standing beside a copy machine. She must be here to collect her things, I decided. “Aren’t you supposed to be in Philadelphia?” I joked, proud of myself for remembering the city she was moving to. Sara peered at me through plastic-rimmed glasses. “I’m not Sara,” she said. “I’m Holley.”

“Oh, right!” I said, hoping that Holley assumed I’d merely gotten their names mixed up when, in reality, I had thought — for months — that two of my co-workers were the same person.

“Everyone at work looks the same,” I later complained to Steve. “They’re all white girls with hipster glasses and ModCloth clothes.”

“You just described yourself,” Steve observed. He was right, but missing the point. Everyone at work literally looked the same to me, just as everyone always does.

Last year, I was trailing behind Steve — now my husband — in a grocery store when he grabbed a jar of store-brand peanut butter from a shelf. I plucked it out of our cart and examined the label.

“Since when do you buy generic?” I demanded.

Steve jumped away from me, his eyes wide with fear and surprise. It was an expression unlike anything I’d seen cross my husband’s face before — because, I belatedly realized, this man was not my husband.

I dropped the peanut butter jar and sprinted off — leaving this poor stranger utterly perplexed. When I found Steve in the frozen-food aisle, I told him what had happened.

“It’s because you have the same coat,” I explained. “Good thing you have different cars, or I might have gone home with him.”

“You have no idea what my car looks like,” Steve said.

He would know. Steve has learned that I will stand on the curb squinting into every car that passes by if he doesn’t honk or wave. I’d long assumed that only car fanatics could identify cars on sight, but, by then, I was beginning to understand that my visual world is a lot different from everyone else’s. After all, I had been quicker to notice the wrong label on a jar of peanut butter than the wrong face on my husband. That doesn’t happen to normal people. And instead of smoothing my mistake into a funny story, for the first time I saw it as evidence that something might be wrong with my brain.

This spring, I found out that I have a rare neurological disorder known as prosopagnosia, or face blindness. This discovery sent me on a journey that I thought, at first, would be a lark. After all, I’m a happy, successful adult — who cares if my brain isn’t quite like everyone else’s? What I didn’t realize was that this diagnosis would make me question all the stories I’ve ever told about myself, the very fabric of my identity. It felt like I’d bought a ticket for a Ferris wheel and ended up being launched into space.

I first learned about face blindness in 2010, when I read an article by Oliver Sacks in the New Yorker. Like me, Sacks had long assumed that his difficulties remembering people were the result of general absent-mindedness. It wasn’t until halfway through his life that Sacks — a neurologist! — realized that he had a neurological disorder. I read with astonishment as he described moments from his life that could have been lifted from mine. We’ve both, for instance, accidentally snubbed our respective therapists and were later forced to unpack the incidents at length.

“It’s not just you,” I said to Dr. Jadin during a session. “Sometimes I don’t recognize my own mother.” That wasn’t exactly true, but I did mistake my aunt for my mom last Thanksgiving. I’m told the two don’t look very much alike, but they became identical to me when my aunt dyed her hair blond.

Despite these similarities, I was hesitant to diagnose myself with Sacks’s disorder. For one thing, it seemed presumptuous to think that I had the same condition as this world-famous scientist and science writer. Also, his experience didn’t quite line up with mine. As Sacks writes: “I think that a significant part of what is variously called my ‘shyness,’ my ‘reclusiveness,’ my ‘social ineptitude,’ my ‘eccentricity,’ even my ‘Asperger’s syndrome,’ is a consequence and a misinterpretation of my difficulty recognizing faces.”

This didn’t sound like me at all. I am not the least bit shy — in fact, I talk to strangers every day. Sometimes it feels like all I do is talk to strangers.

I tossed that New Yorker into my recycling bin, but the topic of face blindness lingered. On occasion, I even connected it to myself, saying, “Sorry, I’m a little face blind,” when I couldn’t remember someone, but I meant it as a joke, a comic exaggeration.

One day I was thinking about the grocery store incident and I started Googling prosopagnosia. Then I began searching medical databases and emailing scientists, asking them to send me the full text of their studies if I couldn’t find them free online. Printouts piled up on my desk until I had more than I could possibly hope to read. Why was there so much research on such a rare disorder?

The 11th floor of the Boston VA hospital is not very hospital-like. It smells of sawdust instead of disinfectant, and the bulletin boards are covered with research posters. It’s also library quiet, except for the sotto voce conversations of serious-looking 20- and 30-somethings — grad students, I guessed.

I’m looking for either Anna Stumps or Alice Lee — two research assistants who have spent the past day and a half shepherding me through facial-recognition tests to determine whether I will get into a training program for face-blind people. One is blond, the other brunette, but I don’t quite remember what either of them looks like. I sit on the floor — there are no chairs — and beam a warm smile at every young, long-haired woman who passes by. One of them eyeballs me warily. I wonder how many other people I’ve creeped out.

After 10 minutes, I email Anna, who tells me that I am on the wrong floor. When I find her on the 12th floor, we walk down the hall to my appointment with Joseph DeGutis, the lead researcher of the face-blindness study I have come to Boston to participate in. He is a neuroscientist with a joint appointment at Harvard Medical School and the Boston VA.

DeGutis, a young, athletic man, stands up from his chair and thanks me for coming. I know I’m going to have to find him later, when we meet up for my fMRI brain scan, so I try to memorize his face — handsome, if a little wolfish.

“So am I face blind?” I ask.

“We think you have mild to moderate prosopagnosia,” he says. DeGutis doesn’t want to elaborate because knowing too much about the experiment could taint my data. “We’ll tell you everything you could ever want to know when you’re done.”

Prosopagnosiacs can be tough to recruit for studies, he adds. They are so good at working around their disability that they trick everyone into thinking that they are normal, including themselves. And when they do recognize that something is amiss, it’s hard to convince anyone else of the fact. It’s so difficult to describe how you see the world because you don’t have anything to compare it to. Plus, early tests of facial recognition were defeated by prosopagnosiacs who used hair and ears and facial expressions to remember who was who.

Aha! This is why I’d spent the past day and a half looking at pictures of blank-faced young men Photoshopped into what looked like nun coifs. I was so tired of looking at faces, I’d taken an Uber to the hospital to avoid looking at people on the train.

“It’s been hard to pin down the deficit, so we kind of overwhelm you with impossible tests,” DeGutis says.

The tests I’d taken that morning truly were impossible. I particularly struggled with one that began with a grid of six faces. Somehow, I was supposed to memorize them and then pick out the ones I’d seen before from lineups of nearly identical mugs. “There’s no way anyone can do that,” I assert.

Actually, the Cambridge Face Memory Test is pretty easy for most people because normal folks have a near photographic memory for faces, DeGutis says. The brain doesn’t bother to do that for any other kind of object. Give people a grid of six rocks, and there’s no way they can pick them out of a lineup. But faces tend to make an indelible imprint in our minds.

For me, face blindness means being a little people blind. I will see a person who seems to know me, and I will greet them warmly and hope that, at some point, they say something that clues me in to who they are.

This is possible because of an olive-size lump of brain located just above and behind each of your ears — the fusiform face area. The FFA seems to come programmed with information about facial configuration — two eyes above a nose above a mouth. Researchers shining lights onto the bellies of pregnant women have found that third-trimester fetuses orient to this pattern, as do babies who are just a few hours old, DeGutis explains.

“Even before you’re born, you have this kind of proclivity toward faces,” he says. This is also why people see faces in electrical outlets, on the front of cars, on burned toast — basically everywhere two dots appear over a line.

Although we are born with basic facial-recognition software, we have to tune it by scrutinizing the faces around us, DeGutis adds. This is why people who are mostly exposed to faces from their own racial group sometimes think (but hopefully don’t say) that so many of the people from another group look alike. It’s also why people who are born blind but gain the ability to see as adults often end up face blind.

A few people become face blind when they have an FFA-damaging stroke, but most face-blind people simply seem to be born with faulty FFAs.

“There’s a genetic component,” DeGutis says. “Is anyone in your family face blind?”

“Not as far as I know,” I say. “But I am stereo blind.”

My eyes are so badly misaligned that my brain can’t combine the two images into one mental picture. Because I’m always seeing out of one eye or the other, my world is a little flat. 3-D movies are lost on me, and I’ve never once caught a flyball.

“That could definitely be related,” DeGutis says. It’s not the whole story, though — 6 percent to 12 percent of people are stereo blind, but only about 2 percent are face blind, and the two don’t always go together.

An interesting thing about people who are born face blind — the so-called developmental prosopagnosiacs — is that they are otherwise normal. In DeGutis’s experience, prosopagnosiacs tend to be smarter than average, perhaps because they often have lonely childhoods with lots of time for reading, thinking and other solitary pursuits.

“It’s just this very specific problem in a specific brain area,” he says. “From a scientific level, it’s one of the most specific things going on in the brain that we know about.”

This is why there’s so much prosopagnosia research: It provides a conveniently small target for scientists’ hypotheses and brain-imaging equipment, and it could eventually shed light on more complicated and debilitating disorders.

“I think this could really unlock a lot of understanding about how the brain develops,” DeGutis says.

“So curing face blindness isn’t exactly the top priority?” I ask.

“Some people have tried giving prosopagnosiacs oxytocin — which is kind of a trust hormone, but it has a dark side,” he says. “People got better at recognizing their own race, and worse at recognizing others.”

DeGutis and his colleagues have also tried stimulating the FFA by applying a weak electrical current through the scalp. “It didn’t work at all,” he says.

However, there is one treatment that has shown some promise: a training program that DeGutis created as a graduate student at Berkeley that teaches face-blind folks to make quick judgments about the spacing of facial features. DeGutis tested the computer-based program on a face-blind friend of a friend and was stunned when it worked. “I was like, ‘Oh my God!’ ” DeGutis recalls. “ ‘Science is amazing. This is the best feeling ever. We might have actually helped someone.’ ”

Being face blind means living in a world full of strangers. The fact that some of these people are acquaintances and even friends is no solace. It’s actually a source of constant anxiety. One face-blind man I read about walked around with his eyes downcast to avoid chance encounters with people he knew but couldn’t recognize. This earned him a reputation for being aloof, which made it even harder for him to make friends.

There’s only one failproof way for face-blind people to avoid social embarrassment, and that is to stay home. Wracked with social anxiety, many face-blind people — Oliver Sacks included — avoid parties and networking events, and their friendships, love lives and careers can suffer as a result. The most tragic cases dig themselves into a trench of loneliness that’s difficult, if not impossible, to escape.

This was the path I was going down until my dad gave me some crucial advice. I was 19, home from my first semester in college, and we’d just finished grocery shopping.

“Well, that was rude,” he said when we got into his car.

“What?” I asked.

“Your buddy Susan Zartman,” he said. “You just walked right past her.”

“Oh, that was Susan?” I asked. A girl with short brown hair had waved to me in the store. “I said, ‘Hi.’ ”

“You said, ‘Hey-ay,’ ” my dad said, mimicking my limp, singsong greeting. “You do that a lot.”

“She’s not my buddy,” I argued. “I haven’t seen her since middle school.”

I later found out that Susan had continued with me to high school, and that she’d been a little hurt when I started treating her like a stranger. Something had happened — perhaps she’d gotten a haircut or glasses — that made me unable to connect high-school Susan with my middle-school friend. And when I stopped seeing her regularly, she simply faded from my mind. In fact, I had kind of forgotten Susan existed.

There’s some evidence that faces act as the brain’s file folder for all the other information you gather about people — when and where and how you met; their favorite bands; the name of their last boyfriend; and why they broke up. Because my brain is unable to make a good file folder, these details often get lost at the bottom of the drawer. Some face-blind people can hitch biographical details to people’s voices, but for me, face blindness means being a little people blind, too.

Of course, I didn’t know any of this at age 19. All I knew was that people I didn’t know often greeted me, and I never stopped to chat for fear that they’d figure out my ignorance and be offended. How, I asked my dad, do you have a conversation with someone you don’t recognize?

“Everyone just wants to talk about themselves,” he said. “Just ask a lot of questions, and they’ll think you’re the most fascinating person in the world.”

I took this tip back to college, and it transformed my life. In one semester, I went from being lonely all the time to having too many friends to fit into my dorm room. All it took was faking that I knew the people who appeared to know me. When I was walking to class, if someone seemed to be looking my way, I smiled. If they smiled, I stopped to chat. Before long, the whole campus was brimming with close, personal friends of mine. That I had no idea who most of them were seemed like a minor quibble.

A few people did stand out from the crowd. My best friend, Melissa, had long blue hair; Thalia and Annette were freakishly tall and usually wet from swim practice. As for everyone else, I was often at a loss, but that didn’t hamper my blossoming social life. When a vaguely familiar-looking woman flopped onto my bed and started talking about her boyfriend woes, I just rolled with it. The trick was not to say anything that would give away the fact that, as far as I knew, this was the first time I was hearing about this jerk of a boyfriend.

My popularity reached its peak when, in my junior year, I was elected house president. (At Smith College, we lived in little self-governing dorms called houses.) I took pictures of all 80 women I lived with and put their faces and names on a bulletin board, claiming it was for everyone’s benefit. I also kept a set of photos and wrote the names and hometowns of my classmates on the back. Despite nightly drilling with my flashcards, I never really learned many of their names. I did, however, link everyone’s names to their hometowns.

“… And then Melissa used my hairbrush again …” the strange woman on my bed complained. “Melissa from New Hampshire?” I asked. There was no reason for me to bring that up, but I was so pleased with myself for remembering something, anything, that I couldn’t help but blurt it out.

Today, as in college, I have many acquaintances but just a handful of close friends — all of whom are distinctive-looking. My friend Miriam is a pixie with long purple hair; Sieren is shockingly tall and thin; Steve is a 350-pound giant of a man.

More typical-looking friends appear in my consciousness like slow-developing photos. My friend Dani tells me that I walked home from yoga with her many times before I was able to pick up our conversation where we had left off. She’s unusually perceptive. A lot of my friends don’t believe me when I tell them I’m face blind. “But you can recognize me, can’t you?” they say. The answer is: sometimes. If you’re in the right context, in good lighting and wearing your usual glasses, my brain will probably put the clues together and come up with a name. If you’ve popped up somewhere unexpected or gotten a haircut, there’s a good chance I won’t. What I will see, instead, is a person who seems to know me, and I will greet you warmly and hope that, at some point, you say something that clues me in to who you are.

I have spent my whole life pretending that I know what’s going on and trusting that I will eventually figure it out. This comfort with uncertainty is perhaps prosopagnosia’s greatest gift — and most vexing characteristic.

A few weeks after returning to D.C., I receive an email from DeGutis’s assistant, Alice Lee, who thanks me for coming to Boston and invites me to take part in a 30-session computer-based training program designed to help face-blind people improve their facial-recognition skills. I didn’t know it at the time, but the researchers had limited this part of the study to those with the very worst prosopagnosia, and I qualified.

Each training session begins with a grid of 10 faces — actually, variations on the same face, with some of the features shifted by tiny increments. A zigzag line separates these nearly identical mugs into two groups: In group 1, the faces have eyes and mouths that are spaced farther apart; in group 2, the faces have more compact features.

I study the faces for a few minutes and then press a button to begin. The grid disappears, and is replaced by a slide show of individual faces that I must identify as belonging to group 1 or 2 by pressing “1” or “2” on my keyboard. It’s a weird activity, but I know from reading DeGutis’s earlier work that it’s supposed to teach me to focus on information-rich areas of the face and make fine distinctions on the fly.

The first round is a disaster. All the faces look the same, and I categorize them about as accurately as a blind person would. For the second round, I try using the white crescents of my fingernails to measure the distances between features. This analytical approach doesn’t work at all — time often runs out and the screen flashes red. By the third round, the faces are starting to look a little distinctive, but the computer is varying their size — presenting some pictures at postage-stamp dimensions, and others at index-card size. Apparently, I’m supposed to memorize the relative distance between features — something that normal people do without even trying, but for me, it feels all but impossible. At the end of the hour, I am nearly crying in frustration.

On my second day, I name the two groups the Steves and the Bobs, and attempt to attach feelings to them. The Steves, with their compact features, seem smart to me. I like them more than the dumb Bobs, with their raised eyebrows and low, silly-looking mouths. This strategy makes the task more interesting, but my score suffers.

One week in, I email Alice, begging for help. “Do I need to make and study flashcards before doing the computer tests?” I ask.

“Nope, please do not create any flashcards or do any other face studying … because it could become a confounding variable and bias your results,” she replies. She also tells me to go faster — each session is supposed to take 30 minutes, and I’m spending an hour on them. This advice does not strike me as particularly helpful.

This whole investigation has reopened a mystery from my past: Why didn’t I have any friends when I was a kid? My old verdict — that I was weird and kids are mean — was suddenly in question.

For weeks I flail and fail and nearly quit. Then, around week 10, I discover a winning strategy. Instead of trying to assess each face as a whole, I divide it into halves, top and bottom. Then I decide which of three positions (high, middle or low) describes the eyebrows, and which of four positions (highest, middle-high, middle-low or lowest) describes the mouth. I also memorize which pairs of characteristics belong to which group.

I’m lying in bed stabbing at my keyboard one night when my husband, Steve, gets fed up. He’s next to me working on his own self-improvement project: watching every episode of “Brooklyn Nine-Nine.”

“How long do you have to do this?” Steve asks.

“Forever, probably,” I reply. Even if I’m among the 50 percent of face-blind people who improve through training, the effect will fade if I don’t continue to do occasional booster sessions, I explain.

“I mean, how long do you have to do this tonight,” Steve clarifies. I’m muttering to myself and it’s annoying.

My scores were soaring, but my real-world facial-recognition skills remained dismal. Toward the end of the training program, I apparently sat right next to my friend Dani at a coffee shop and didn’t recognize her. She informs me of this a few days afterward. “You looked right at me, too,” she says.

Later that week, something unexpected happens: A neighbor of mine walks into the coffee shop where I’ve parked myself for the morning, writing a story and not wanting to be disturbed. I look up, realize I know him, and then quickly avert my eyes. For perhaps the first time in my life, I have snubbed someone on purpose.

After finishing the training, I return to Boston for another round of tests and scans.

“How did it go?” Alice asks, firing up a chunky gray laptop.

“I didn’t notice a big difference,” I say, “but when I did recognize someone, I felt more certain about it.”

Alice nods inscrutably, and then leaves me alone to complete new versions of the same tests I’d taken on my first trip to Boston. Before I start, I try to recall her face. Is it oval or square? Are her eyebrows high or low? I have no idea. As far as my memory is concerned, she’s just a young woman with long dark hair. Soon nothing is left of her besides the sound of her footsteps as she walks away from me down the long hospital hall.

Three weeks later, DeGutis calls me with my results while I’m at work.

“So am I legit face blind?” I ask.

“Yes. Your ability to learn new faces is among the worst of our prosopagnosiacs,” he replies. “You were one of the lowest scores that we’ve registered so far.”

This comes as a relief. I had been worried that the tests would show that I am actually good at facial recognition — and mean that I can’t remember people because I’m just self-centered.

“What did my brain scan say?” I ask. That, to me, seems like the big question. I could have done poorly on the tests because I subconsciously wanted a cool diagnosis. But no one can fool an MRI machine.

“So this is really interesting,” DeGutis says. “We found that your fusiform face area is actually … thicker than average. Thick sounds good, but … thinner is better for your face area.”

Children start out with dense FFAs, but as the brain determines which neurons are useful and which ones are just getting in the way, it thins them out. This so-called neural pruning seems to have stopped short in my brain, in this one area.

“You have the fusiform face area of a 12-year-old,” he says.

“And the facial recognition ability of, what, a 3-year-old?” I ask.

“So I would say maybe like a mediocre or below-average macaque,” he replies.

I guffaw, but I’m in shock.

If that’s the bad news, here’s the good: After 30 hours of training, my facial-recognition skills have improved significantly.

“You were really on the low end of prosopagnosiacs,” DeGutis says. “You were really struggling, and the amount that you went up on these tests after training was kind of remarkable. If you’d been this good when you came in, you wouldn’t have gotten into the study.”

They weren’t really sure how I had managed this feat. The follow-up tests showed that my face perception was still terrible. I wasn’t able to match a face with the exact same face at a slightly different angle, even when the first face was still in front of me. But whatever sketchy information I could glean, I was now holding onto ferociously, through some unknown strategy or sheer force of will.

“Maybe you’re doing more of this associative encoding and paying attention to kind of compensate a little bit more,” he says. “But I don’t think we fixed your perceptual deficit.”

After thanking DeGutis and saying goodbye, I put on sunglasses and flee the office. I cried the entire time we were on the phone, and my face is a wreck.

“What’s wrong?” Steve asks over dinner that night. His compassion releases a new torrent of tears.

“I have the fusiform face area of a 12-year-old and the facial-recognition ability of a capuchin monkey,” I wail, misremembering my specific type of primate.

It’s not the monkey brain news that’s getting me down, I add. The bigger issue is that I’ve always thought I was in charge of my life — that I was a writer and a reporter because I had decided on that particular career path. But maybe I’d been pushed in this direction by my faulty brain, which had resulted in the lonely childhood that I got through by reading a lot. Then, as a young adult, my prosopagnosia made me an expert at talking to strangers.

“Of course I ended up being a reporter,” I say. “What else was I going to do with that kind of training?”

I blow my nose, a great honking sound.

“I think there’s a way to see this as just a really exciting exploration of why you are who you are,” Steve ventures.

“You’re probably right,” I say.

For weeks afterward, I am a mess. Absolutely anything can bring me to tears. I cry in a museum. I cry at my friend’s kid’s birthday party. I cry when a school bus passes me on my bike. Eventually, the trigger becomes clear: middle-schoolers.

This whole investigation has reopened a mystery from my past, one that I thought I’d long ago closed: Why didn’t I have any friends when I was a kid? My old verdict — that I was weird and kids are mean — was suddenly in question.

In the spirit of exploration — why stop now, right? — I do something a little impulsive. I write a note, via Facebook, to my former classmates, telling them that I have just been diagnosed as face blind, and asking if that had anything to do with my unpopularity.

“Do any of you who were there remember anything relevant?” I ask. “I’m really just curious at this point. I’m a happy, successful adult now and have a thicker skin. So if you recall that I was an off-putting weirdo, or that no one was friends with me because I smelled, I promise I won’t be offended.”

Replies roll in quickly. “You had friends! I was your friend!” one classmate writes. I would argue with her, but she follows up with a memory of making saucepan fudge at my house. That tracked. When I was 10 or so, I got around a household ban on sweets by making my own candy.

Other people recall that I wasn’t particularly unpopular, but that I was standoffish. “You always seemed to just be content doing your own thing,” one gal writes. “You always beat to your own drum,” another says. A third woman claims that she’d tried to be friends with me, but that I never seemed to warm up to her. “We hung out a little and I thought you just didn’t really like me,” she says.

The implication is stunning. How many friendships had I missed out on because of my face blindness? How many do I still miss out on, despite my high-caliber friendliness? I will never know. Lucky for me, not knowing is sort of my specialty.

In July, I celebrated my 40th birthday with 60 or so of my closest friends, many of whom I wasn’t able to recognize on sight. I was fine with that, and, presumably, they were, too. Most of them have no idea that I am face blind; they probably just think that I am absent-minded. Or maybe I’ve been so good at faking it that it has never occurred to them that they all look pretty much the same to me.

My hard-won gains in facial recognition are, most likely, already fading. I could do periodic booster sessions to keep my skills sharp, but I’m not planning on it. I’d rather spend that time doing something I enjoy, like playing violin or looking at birds. I love sitting in the park by my apartment, watching these beautiful creatures go about their day. I get such a thrill identifying them.

Sadie Dingfelder is a staff writer for The Washington Post Express.

Postdoctoral fellow Maruti Mishra attaches electrodes to Sadie Dingfelder’s head to measure the activity in her fusiform face area. (Photo by Anna Stumps)

Clarification: A photo caption in this story originally described Maruti Mishra as a research assistant; she is a postdoctoral fellow.