As I've gotten older, I've noticed how many known things I forget. The names of people's spouses, book titles (and often, their content). It's an unsettling feature of aging, but the more I think about what I've forgotten, the more I'm reminded of an undersung cognitive phenomenon that might explain the reason better than aging does.

The Zeigarnik Effect focuses on what we're prone to remember and why—and it's not what you'd expect—although it makes complete sense.

Let’s begin in Berlin.

It's 1926, and Bluma Zeigarnik is in a restaurant sharing a meal with her mentor Kurt Lewin—one of the founding figures of modern social psychology—and possibly other students (accounts differ). She's a graduate student from Russia, studying psychology. (She will later become a clinical pathopsychologist, a field she helped pioneer and develop.)

The waiter has nothing to write with, and Professor Lewin observes his ability to remember and track their complex orders. He recalls who ordered what, and who hadn't yet paid. Yet, what struck him was how much the waiter forgot once the check was settled and the plates cleared. The waiter seemed unable to recall not just details of their orders, but the patrons themselves.

After sharing these observations, Zeigarnik was intrigued enough to pursue a field of inquiry.

Building upon Lewin's emerging field theory, which emphasized the dynamic nature of human motivation, psychological environment—or "life space"— and the tension systems within the mind, Zeigarnik conducted a series of experiments to test whether interrupted tasks were actually more memorable than completed ones.

She gathered 164 people—children, students, even their teachers—and handed them a series of 18 to 22 small tasks. Some were puzzles, some arithmetic, some hands-on projects like building little cardboard boxes. Half the time she allowed them to finish; half the time she cut them off, just as they were getting somewhere.

Later, when she cleared the table and asked them to recall what they’d been working on, the results were startlingly consistent. Unfinished work stuck. In her first set of experiments, 26 of 32 people remembered the interrupted tasks best; in her replication with another 15 subjects, the pattern repeated almost exactly. Even in larger groups the story held: of 47 adults, 37 recalled the interrupted tasks most vividly, and among 45 schoolchildren, 36 did the same. On average, the uncompleted tasks were remembered nearly twice as well as the finished ones.

What we leave undone, she discovered, has a peculiar hold on the mind.

Her theory was this: Incomplete tasks create a state of mental tension which persists until the task is completed. The motivation caused by this tension makes us better able to remember incomplete tasks.

Complete something? The mental tension dissolves, and the details fade (hence, my forgetting things! Maybe the logic doesn't hold up, but I feel like names I've known—and haven't "used" for a long time—might be "marked" as completed somehow).

At the time, her findings challenged prevailing theories of memory, which suggested that repetition was the key to memorability. Instead, Zeigarnik showed that the state of incompletion itself played a crucial role in how well information was retained.

The Zeigarnik Effect isn't about how strong your memory is—it's about how your brain prioritizes information. Incomplete tasks end up staying active in your awareness, irrespective of how good your memory is. Cognitive tension, which refers to a kind of psychological pressure that builds up when a task is started but left incomplete, is at the center of the Zeigarnik Effect.

Cognitive psychologists later built on this idea by introducing the concept of task-related cognitive load. This is the idea that incomplete goals take up working memory space. As Zeigarnik noted, it's not just memory that's affected. Focus, mood, and sleep are also affected. When left unmanaged, a pile-up of incomplete tasks can feel like an invisible burden.

Think about your own mental state right now. How many browser tabs do you have open? How many projects are sitting half-finished on your desktop, on your desk, in your mind? How many conversations ended mid-thought because someone got distracted by their phone?

We're living in an age of perpetual incompletion, and it's exhausting. Every unfinished email, every half-read article, every project you started but didn't finish, is creating one of those mental tensions Zeigarnik identified.

No wonder we feel mentally scattered and overwhelmed.

But what if we could turn this against itself? What if we could use our brain's obsession with unfinished business to actually get more done?

The next time you're procrastinating on something big, don't commit to finishing it. Commit to starting it for precisely five minutes. Set a timer. When it goes off, stop—even if you're mid-sentence.

Here's what happens: your brain doesn't like that open loop. It will keep chewing on the problem in the background. When you sit down the next day, you won't be starting from zero. You'll be continuing something your subconscious has been working on. (If you've ever read On Writing by Stephen King, you'll know he uses this as a writing strategy.)

This one feels counterintuitive, but it's powerful. When you're working and things are flowing well, stop. Leave yourself a breadcrumb trail—a half-finished thought, a problem you know how to solve but haven't solved yet. Hemingway supposedly did this with his writing, stopping mid-sentence when he knew what came next. The next day, he could start by finishing that sentence and riding the momentum forward. (Some people call this "The Hemingway Bridge.”)

If our brains are drawn to incomplete patterns, we should use this. Instead of orderly, completed to-do lists, create visual reminders of what's undone. Empty checkboxes are cognitively louder than plain text. Progress bars that aren't full create tension. Even something as simple as writing "Call Sarah..." and leaving it hanging will stick in your mind better than "Call Sarah about dinner."

When you're reading or studying something new, resist the urge to immediately look up every answer. Write down questions as they occur to you, but don't resolve them right away. Let your curiosity build. Your brain will be primed to grab those answers when you encounter them. The tension of not knowing makes the eventual knowing much more memorable.

Here's the rub: the Zeigarnik Effect only helps if you eventually finish things. Chronic incompletion doesn't make you productive—it makes you anxious.

End each day by consciously deciding what stays open and what gets closed. Write "DONE" next to finished tasks. Cross out things you're choosing to abandon. Give your brain explicit permission to stop thinking about certain loops.

You'll feel a release in cognitive tension.

Zeigarnik's discovery touches on something more profound about how humans work. We're not filing cabinets, designed to store complete information. We're problem-solving machines, energized by the need to resolve and fill gaps.

The shows that keep us up late by feeding us cliff-hangers work on this principle. They create a curiosity gap that we feel compelled (and often powerless) to close. The problems that obsess us are the ones we almost, but don't quite, understand. The goals that motivate us are the ones we can see but haven't reached yet. (Think about the long arc of an artist’s life—the themes that keep repeating in their work? Unfinished business is an artistic obsession.)

We forget completed things because our brain is making room for active problems (Yes, I am taking ALL my comfort from this). The question then isn't how we remember everything, it's what we should strategically choose to leave unfinished.

The reason I remember the Zeigarnik Effect after all these years is that I held it in my mind as incomplete—I remember hearing about it, and recalled its vague contours, but I hadn't closed the loop on researching it—until now.

Some loops are worth keeping open.

If Bluma Zeigarnik interests you, I've managed to get my hands on a 13-page preview of her memoir, which can be found here.

Until next week, I will remain…

Cover illustration from Raphael Pequeno.