Why can't we remember being babies?

To understand why we don't remember being swaddled as infants -- or just about anything else from our baby years -- we must first understand how our earliest experiences are imprinted on the brain.

Infants rely on both semantic and episodic memory. Semantic memory is the processing of ideas not drawn from personal experience (names of colors, or dates of events in history, for instance). Episodic memory is drawn from personal experience (what the first day of school was like or where you were on 9/11). Over time, the episodic memory may become semantic memory, so that you don't remember you learned about dogs from playing with your first dog – you just know what a dog is [source: Zimmermann].

Scientists think the reason we can't recall events from babyhood may be because of the way memories are stored and accessed. While both semantic and episodic memories are stored in various regions of the brain's surface, known as the cortex, it isn't until ages 2 to 4 that the brain's hippocampus networks all these disparate regions into one centralized source of information. These connections allow children -- and adults -- to recall memories for the long term [source: Shouse].

Does this window into early childhood memories really explain why we can't remember being babies? One 2014 study blames the circuits in our brains for betraying our ability to remember babyhood.

Results published in the journal Science shed new light on the amnesia older children and adults have about their baby years. The study centered on the constant formation of new cells in infant brains. The process of growing new neurons, known as neurogenesis, occurs throughout a mammal's life. However, babies produce new neurons at an accelerated rate. And where does all of this production take place? The hippocampus, which is what we rely on to access all the memories we're storing [source: Locke].

Using rodents as test subjects, researchers surmised all these new neurons cropping up in the hippocampus disrupt its formation and access of memories. In fact, when the researchers used drugs to decrease the number of new neurons formed by the rodents, the rodents were able to remember better. Increasing the number of neurons had the opposite effect [source: Locke].

Even with all the research surrounding early childhood, there aren't definitive answers as to when -- exactly -- we lose the memories of being a baby. Even among your circle of friends, there are likely to be those who can remember childhood experiences more vividly, and from an earlier age, than others.

One intriguing hypothesis is that the ability to remember being a baby may be linked to left- and right-handedness. A study published in the journal Neuropsychology suggested people who perform tasks with both the right and left hands may be able to remember childhood memories formed at an earlier age than those who are solely right-handed [source: Winerman] .

In the study, about 100 collegiate participants who were mix-handed (ambidextrous) or right-handed were asked to write down two memories from early childhood. They were instructed that one memory should be an event they personally remembered, while the other should be an event retold to them by their parents or another witness, which would later be verified as true. The exercise, designed to measure semantic and episodic memories, revealed the mix-handers' personally remembered (episodic) memories were recalled from an earlier age than the right-handers memories. In addition, mixed-handers could retell memories retold to them from an earlier age, too. The suspected reason? Mixed-handers may have more communication between the brain's hemispheres [source: Winerman].

The corpus callosum, a nerve bundle that connects the two sides of the brain, becomes functional at age 4 or 5. At about that same time, childhood amnesia begins to disappear as episodic memories become encoded on the left hemisphere of the brain and retrieved from the right. (Semantic memories are both encoded and retrieved in the left hemisphere.) The study hypothesized that the increased communication between the right and left brain could allow mix-handers to encode and retrieve early memories more efficiently than right-handers, and that they may have a thicker corpus callosum to boot [source: Winerman].