I should have been surprised that I couldn’t remember the birthday of the man to whom I’ve been married for almost thirty years, a man I love with all my heart. For years, his birthday has also been the code I’ve used to unlock my cell phone. But I’m not easily surprised nowadays. There are lots of things I can’t remember. Numbers, in particular, escape me, and dates are difficult too.
Since I’m going in for radiation tomorrow, Kasia and I decided to celebrate Mirek’s birthday a day early. And now, as I sit here in the restaurant, I keep staring straight ahead. The waitresses are curious as to what I’m doing, I can tell. With kind smiles, they ask if I need anything more, if they can help. I thank them but shake my head. The sushi chef across the counter from me, a tall, handsome man, works on a sushi roll, cutting and chopping colorful ingredients, rolling sticky rice wrapped in seaweed with his bare hands, squeezing fancy sauces on top. As he dips his fingers in this and that container, he glances at me with a shy smile.
It’s been twenty minutes since they delivered our takeout order to me, a big brown bag with a tray of creamy sushi rolls filled with eel, salmon, and whitefish decorated with avocado, wasabi, seaweed, sesame seeds, and other spices. I’m still trapped here at the counter, staring at the bill and trying to figure out the tip.
I’ve made no progress whatsoever. I see lots of numbers scrawled on a small sheet of paper but they mean nothing to me. I read the numbers but don’t understand what to do with them. I do remember that a tip should be 20 percent—that concept springs to mind—but I don’t understand the notion of percentages. I remember only a bare fact: 20 percent. Without more context, it is meaningless. What does 20 percent signify? How does one calculate it?
I scrutinize the bill. What was the cost of our sushi? I think that’s it, that number there, seventy. But if that’s how much the food cost, how much is the tip?
I turn these questions over in my mind, desperate to find an answer that doesn’t come. I change my strategy and start playing with random numbers in my head, then try them on my tongue. “Thirty dollars?” I whisper. “Or twenty dollars? No, that doesn’t sound right.”
I throw looks in the direction of the restaurant’s front door, through which Kasia disappeared nearly half an hour ago. She went to get the car, I remember, so we wouldn’t have to carry the tray too far.
Why doesn’t she come back?
I feel helpless. I open my wallet and find a ten-dollar bill.
Okay, maybe ten dollars.
I resign myself to the amount that’s available, a random bill that I place on the counter. I quickly leave so I won’t be stopped and questioned if it’s wrong. I feel like a crook.
Kasia has been sitting in the car near the entrance to the restaurant all this time.
“What happened, Mom? What were you doing in there for so long?” she asks.
I don’t know how to reply. “Oh, nothing,” I say, trying to sound nonchalant. “Do you think ten dollars is okay for the tip?”
“You left a tip on a takeout order?” She sounds surprised.
“Why not? But I had trouble calculating the right amount.”
She gives me a bewildered look. “How much was the sushi?” she asks.
I hesitate. “Seventy dollars,” I say. I feel relieved that I can recall.
“You couldn’t calculate twenty percent of seventy dollars?”
“No.” Suddenly, I feel inadequate.
As we drive home, she starts quizzing me. “What’s a hundred and twenty divided by three?”
I ponder it. “I don’t know,” I say.
“What about twelve divided by three?”
“I—I have no idea.”
“Can you add five and ten?” she tries.
“Fifteen!” I shout, overjoyed.
“Eighteen minus five?”
“I don’t know. Twelve, maybe?”
We experiment with simple arithmetic problems all the way home. We discover that I can add, as long as the numbers are simple. But any kind of subtracting, multiplying, or dividing is impossible, no matter how basic the question. These calculations are simply over my head.
Celebrating Mirek’s birthday dinner with his favorite food, sushi. I’d just discovered I couldn’t calculate the tip for the sushi or do other kinds of simple math.
When we walk into the house, Kasia and I don’t talk about it anymore, and we don’t mention it to Mirek as we celebrate his birthday with our sushi meal. Kasia doesn’t tell me until much later, but it deeply pained her to see me so deteriorated, so altered, from the strong-minded and accomplished person I used to be: her sharp-witted mother, the one who taught her math and logic as well as the importance of honesty and how to enjoy her life. She doesn’t want our roles to change. She doesn’t want to be a physician examining my symptoms and observing my strange new behaviors in an attempt to understand what’s wrong. She wants her loving, fun, competent mama. Not this confused, angry, self-absorbed impostor.
As Dr. Aizer will explain to me much later, my compromised math ability—which is called dyscalculia or acalculia—is most likely related to the lesion and inflammation in my parietal lobe, the area located just behind the frontal lobe on top of the brain. Together, the frontal and parietal lobes make up about two-thirds of our species’ highly evolved neocortex, which comprises the four lobes of the brain. Lesions or defects in the frontal and parietal lobes have been linked with dyscalculia in patients with early stages of dementia.
Scientists have been able to trace different aspects of numerical processing, such as multiplication and subtraction, to different subregions of the parietal lobe. Thus, people with lesions in a particular area of the parietal lobe may show deficits in the ability to perform one type of calculation but not others. In my case, I seem to be able to add simple numbers. But I cannot handle
