Have you ever thought of something, whether it was a funny meme or a major life event in the past, and thought to yourself, “Why do I remember this? Why do memories exist?”

In this article, I’ll be explaining how the brain forms memories, why we need them, and why we forget some. I’ll also give a few fun facts about memories.

How the Brain Forms Memories:

Memory is the reactivation of a specific combination of neurons in the brain. When a person experiences something, these neurons form and activate. When they (e.g., see, hear, think) of that experience again, that group of neurons reactivates and becomes a memory.

There are two main types of memory: long-term memory and short-term memory. Long-term memory is when the neurons are reactivated over a period of days to a lifetime. Short-term memory is when the neurons are reactivated for about fifteen to thirty seconds. They are then forgotten after those few seconds.

Why We Need Memories:

Without memories, we could never survive in this world. We need memories to remember dangers in the world, how to survive, and how to make good decisions. If everyone’s memories disappeared, we would only be living in the exact present moment and not know how to eat, drink, walk, etc. We’d all die in a short amount of time.

Memories are also essential for learning and building personal identities. Without memories, we could never learn skills, and would never remember our experiences. Memories are important in shaping different peoples’ personalities, identities, perspectives, etc.

Why We Forget:

When neurons rarely or never get used after an experience, the neurons belonging to that memory fade over time. While forgetting something is often viewed as something negative, it’s actually very important. If you never forgot anything, it would be harder to think fast when needed because, when trying to think, your brain would flood with everything that has ever happened to you. It would be harder to make quick decisions, which is especially important for life-threatening situations.

Hyperthymesia is a condition that makes it so you can remember almost everything. Many people with hyperthymesia often have trouble with certain types of creative thinking. This is because creative thinking often requires people to invent new scenarios in their minds. But since lots of people with hyperthymesia almost always think about their past due to having so many memories, they usually have a harder time inventing new ideas and tackling many creative problems.

Fun Facts:

• The average human brain can store 2.5 million gigabytes (2.5 petabytes or 19,531 smartphones) of memories.
• A computer would need a zettabyte of storage to capture all of the brain’s activity. To put that into perspective, that is one trillion gigabytes, or over 7.8 billion smartphones of information. As of 2026, the world has only 221 zettabytes of information.
• When you recall something, the brain rebuilds that memory from fragments of information from different areas of the brain. Since the brain has to rebuild that memory every time you think of it, it could easily change due to emotions, new information, etc.
• Without repeated practice, you forget 50% of what you learn within an hour of learning about it.
• Alzheimer’s disease is a condition caused by the buildup of different proteins between and inside brain cells. This causes memory loss and can make someone forget where they are, ask the same questions repeatedly, forget how to eat, etc. Alzheimer’s is one of the most common reasons for someone developing dementia.
• The average person thinks of about 6,000 thoughts per day.