Try to picture your first birthday party. Maybe you’ve seen photos—cake on your face, pointy hats, people smiling all around you. But can you actually remember being there? Probably not. And you’re not alone. Most people can’t recall anything from their very first years. Scientists call this strange brain blank spot “infantile amnesia.”

But why does it happen?

One part of your brain that helps prepare memories—the hippocampus—wasn’t fully developed yet. Your brain didn’t have the tools to process your experiences clearly and get them ready for long-term storage. You can think of it like a new library, where the librarian isn’t trained yet, and the system for cataloging hasn’t been set up. The library might have some books, but without a system in place to sort and send them to the right shelves, they’re easy to misplace.

Language plays a big role, too. Words give your brain the labels it needs to make sense of experiences and decide where to store them in another part of the brain called the cortex. Without words like “puppy” or “slide,” it’s harder for your brain to tag your memories of your childhood dog or a day at the park and figure out where they go. It’s like you’ve filed a book away in the library without knowing the title—it might be on a shelf, but difficult to find later. 

Most people’s first solid memories don’t stick until around age 3 or 4, when the librarian is trained, the shelves are ready, and new books are correctly labeled. As you age out of babyhood, a big reorganization called “synaptic pruning” makes the “library” work faster and more efficiently, though some early unlabeled books may get lost along the way.

So if you flip through baby pictures and wonder, “Why don’t I remember this?”—just know: You didn’t forget. Your brain was still figuring out how to organize its growing catalog.

Special thanks to Peter Strick, a PhD and the Dr. Thomas Detre Professor and Chair of Neurobiology, for his help with this trip down lack-of-memory lane. 

Read more from the fall 2025 issue.