It’s 3am. You’re on your third lap of the hallway, and you wonder: will they remember any of this? The answer is stranger than yes or no. Your baby is recording this year, all of it. A few years from now, they won’t be able to play it back.

How you test a baby’s memory

The ribbon and the mobile. Researchers tie a ribbon from a baby’s foot to a crib mobile. Within minutes, a two-month-old figures out that kicking makes the mobile move, and starts kicking with enthusiasm. Remove the ribbon, bring the baby back later, and see whether they start kicking again right away:

• 2-month-olds remember for about a day and forget within a week. (For a two-month-old, a week is about an eighth of their life.)
• 3-month-olds still remember after a week.
• 6-month-olds remember for about two weeks.

The reminder. Take a baby who has forgotten. The day before the test, let them simply watch the mobile move for a minute, without the ribbon. The next day, they kick as if they’d never forgotten. The memory was still there. They just couldn’t reach it until something reminded them.

Copying an action. For older babies, a researcher does something odd with a new toy, like touching a box with their forehead to make it light up. Later, the baby gets the toy. If they press it with their forehead, they remembered. 6-month-olds remember for about a day, 9-month-olds for about a month, and 20-month-olds for up to a year.

Even newborns recognize their mother’s voice within days and prefer a story that was read aloud to them in the womb. Babies remember. That part is settled.

So why can’t you remember being a baby?

Almost nobody remembers anything from before age three. This is called infantile amnesia. For a long time, scientists assumed the baby brain simply wasn’t saving anything yet. That idea is now in trouble:

• In a 2025 brain-scan study, the brain’s memory region lit up as infants looked at pictures. The babies later stared longer at exactly those pictures, a sign they remembered them. That region was working.
• In rats, which also forget their infancy, a later reminder can bring an infant memory back, just like the mobile.

The leading idea now is that the memories are saved but can’t be found later. Think of a library whose books go on the shelves before anyone builds a catalog. There are three likely reasons, and all three may play a part:

1. The filing system is still being built. The part of the brain that records when and where something happened keeps changing for years, and each change scrambles the old filing.
2. There’s no “me” yet. A memory needs a sense of “this happened to me,” and that doesn’t really form until around age two.
3. There are no words yet. Adult memories are partly stories. A baby’s memories are sights, sounds and smells, which are hard to look up later.

How much of this is true, and whether those early memories can ever be reached again, is still debated.

What your baby keeps

• Skills. They’ll never remember learning to sit up, and they’ll never forget how.
• Faces and voices. Yours are stored so deeply they don’t need a catalog.
• How the world feels. Whether someone answered when they cried, and whether being picked up was reliable. This isn’t stored as a scene. It becomes their sense of what the world is like.

What this means for you

• Repetition builds memory. The same song, the same silly face, the same laps of the hallway. Repeating things isn’t boring. It’s how babies remember.
• Reminders help. Memories come back with cues, so the photo, the song and the favorite park all help.
• The hard nights won’t be remembered as scenes. What stays is the pattern: someone came.

They won’t remember this year. They’ll be made of it.

Sources

• Rovee-Collier, “The development of infant memory” (1999), Current Directions in Psychological Science
• Barr, Dowden & Hayne, “Developmental changes in deferred imitation by 6- to 24-month-old infants” (1996), Infant Behavior and Development
• Carver & Bauer, “When the event is more than the sum of its parts: 9-month-olds’ long-term ordered recall” (1999), Memory
• DeCasper & Fifer, “Of human bonding: newborns prefer their mothers’ voices” (1980), Science
• DeCasper & Spence, “Prenatal maternal speech influences newborns’ perception of speech sounds” (1986), Infant Behavior and Development
• Yates, Turk-Browne et al., “Hippocampal encoding of memories in human infants” (2025), Science
• Travaglia et al., “Infantile amnesia reflects a developmental critical period for hippocampal learning” (2016), Nature Neuroscience
• Akers et al., “Hippocampal neurogenesis regulates forgetting during adulthood and infancy” (2014), Science
• Howe & Courage, “On resolving the enigma of infantile amnesia” (1993), Psychological Bulletin

This is educational content, not medical advice. For anything about your own baby, talk to your pediatrician.