Why Do We Always Forget Things

We often forget different things, but many of them are ones we’d rather remember—especially when studying or learning, where newly acquired knowledge seems to slip away quickly. How does the human brain handle memory? And is it possible to avoid forgetting?

German psychologist Hermann Ebbinghaus conducted extensive research on human memory long ago. One of his most famous findings is the “forgetting curve,” which describes how the brain learns and forgets. His experiments showed:

• After 20 minutes, 42% was forgotten, 58% remembered.
• After 1 hour, 56% was forgotten, 44% remembered.
• After 1 day, 74% was forgotten, 26% remembered.
• After 1 week, 77% was forgotten, 23% remembered.
• After 1 month, 79% was forgotten, 21% remembered. When we receive new information, part of it is quickly forgotten. Over time, the rate of forgetting slows, but the amount forgotten continues to increase.

When the brain receives information, it first enters short-term memory. Short-term memory lasts only briefly and is quickly lost, but it is extremely useful in daily life. For example, when looking up a phone number, we remember it just long enough to dial, then forget it soon after. Or when reading a long sentence, we hold the first half in mind to understand the second half, then let it go once the whole sentence is understood. Short-term memory is practical and often used, but its capacity is limited and it fades quickly.

Long-term memory forms when short-term memory is consolidated. Its capacity is virtually unlimited, and it can last for years, decades, or even a lifetime. Examples include one’s native language, deeply significant personal events, or basic arithmetic. Long-term memory can be divided into two types:

• Explicit memory (declarative memory): conscious recollection, such as personal experiences, learned knowledge, or news events.
• Implicit memory (procedural memory): Implicit memory is a type of memory that works without conscious recall, allowing us to perform actions automatically. Skills such as swimming, cycling, or driving, once mastered, can be carried out naturally without step‑by‑step thought. Walking home along a familiar route is similar—we arrive without needing to consciously remember each turn. It also includes habits and conditioned reflexes. Brushing your teeth each morning is an example of a habit, while reacting instantly to a sound shows a reflex. These memories are deeply embedded in the brain’s neural circuits, independent of awareness, and they help us act quickly and efficiently in everyday life

When the brain learns something, it first enters short-term memory. If the information seems unimportant, the brain weakens and deletes it. If it matters, it is strengthened and stored as long-term memory. How does this transformation happen?

Reviewing is a crucial step. Going over material just before it is forgotten is highly effective in fighting memory loss, and each review makes the knowledge stick even more firmly than before. Many recommendations are based on the forgetting curve, suggesting reviews at intervals—after 20 minutes, 1 hour, 1 day, 1 week, and 1 month—to help transfer what you’ve learned into long-term memory. Each time you forget something, it shouldn’t be discouraging. Instead, it’s an opportunity to strengthen that knowledge further. With persistent review, information can be consolidated into long-term memory. Learning takes time, and rushing only meets failure.

In addition, association and application play an important role in forming long-term memory. Linking new knowledge with old, or connecting it to real-life experiences, gives new information personal meaning. For example, when you gain a deep understanding of a historical event, you can use it to learn about what happened before or after, grasping the timeline and causes and effects—greatly strengthening memory. Also, when learning a new word, you might go to a relevant setting and apply the word’s meaning through real actions, creating a connection between the word and your own experience.

Good routines and healthy lifestyle habits also help strengthen long-term memory. Balanced nutrition and regular exercise support brain function and promote blood circulation in the brain. Sleep, however, is often overlooked. During sleep, the brain reorganizes and repairs itself, consolidating the information learned during the day and reinforcing connections between neurons. In other words, the studying and reviewing you do while awake are consolidated and integrated during sleep. With sufficient rest, the formation of long-term memory becomes far more efficient.

Forgetting is a completely normal and natural function of the brain. Preserving important information while discarding the unimportant actually benefits human survival. It lightens the brain’s burden, optimizes existing memories, allows us to relearn after mistakes, and helps us move unpleasant experiences. If the brain remembered everything, it would be disastrous, and what’s frightening is that such people do exist. Those with hyperthymesia syndrome can recall every detail of their daily lives—clothing, weather, meals, and countless specifics. Each day they spend enormous amounts of time reliving the past, including embarrassing or painful events that resurface vividly and relentlessly, causing mental distress. Interestingly, despite their extraordinary memory, their learning ability is not high. With so much information flooding their minds, they struggle to focus. Poor concentration makes it difficult to study or master new knowledge, leaving them overwhelmed by endless trivial details.