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The Forgetting Curve

Why We Forget and How to Remember Better​

Why do we forget so much of what we learn? And why do some things stick with us for years while others vanish in days? Over 100 years ago, Hermann Ebbinghaus—a German psychologist and pioneer of memory research—set out to answer this. His discovery of the Forgetting Curve still shapes how we understand learning and recall today, and it underpins the memory systems used in The Hundred.

Who Was Hermann Ebbinghaus?​

In the 1880s, Ebbinghaus conducted a series of groundbreaking experiments on himself to understand how memory works. He created lists of nonsense syllables (like “DAX” or “ZUB”)—deliberately meaningless so that existing associations wouldn’t interfere—and then tracked how long it took him to memorize and later recall them. His results led to two major discoveries:

  1. The Forgetting Curve
  2. The Spacing Effect

Let’s look at each.

The Forgetting Curve​

Ebbinghaus found that we forget most information rapidly after learning it, unless we take action to reinforce it. He plotted this pattern as the Forgetting Curve, which shows how memory decays over time:

  • Within an hour, you may forget over half of what you just learned.
  • After a day, you may remember only a fraction.
  • The decline slows over time, but without review, most content disappears.

Key idea: Forgetting is predictable. And because it’s predictable, we can design systems to counteract it.

The Spacing Effect​

Ebbinghaus also discovered that reviewing information at spaced intervals—instead of cramming—greatly improves long-term retention. This became known as the Spacing Effect, and it’s the foundation of what we now call spaced repetition. Here’s how it works:

  • You review a fact just before you're likely to forget it.
  • Each review strengthens the memory. The time until you forget again gets a bit longer.
  • This effect is very strong when you review at the right moment - but weak when you review too early or too late.
  • Eventually, the information moves into long-term memory with minimal effort (if you get your timings right).

Think of it as reinforcing a trail through the forest. If you walk it regularly, it becomes clearer. Wait too long, and it overgrows.

In the World of The Hundred​

At the heart of The Hundred’s learning system is a spaced repetition algorithm inspired by Ebbinghaus’s findings. As you complete quests and answer quizzes, The Hundred:

  • Tracks what you’ve seen and how well you’ve remembered it.
  • Calculates the optimal time to revisit that knowledge.
  • Presents it again—just before you're likely to forget—through new challenges, quizzes or witlets.

This ensures that new knowledge sticks, without the player feeling overwhelmed or needing to “grind.” And best of all, the AI adapts to your very personal forgetting curves. If you have a great memory you move fast, if you need a bit more time the AI slows down.

The goal? To make remembering part of the game world—not just the result of it. Forget less. Learn more. Keep playing.

Why It Matters​

Ebbinghaus’s work shows that memory isn’t just about what we learn—it’s about when and how often we revisit it. Whether you're trying to:

  • Learn a language,
  • Master historical knowledge,
  • Remember a complex game world,
  • Or just keep your mind sharp

Using spacing and retrieval makes all the difference. It turns temporary recall into lasting understanding.