Why don't we remember being babies?

Your mother's smile as you say your first word or the smell of the candles on your second birthday cake are memories many people would love to hold on to. But almost nobody can recall memories from very early childhood — a phenomenon known as infantile amnesia or childhood amnesia.

So why do we tend to forget these very early memories?

To answer this question, it is important to distinguish between two major types of memory: semantic and episodic. Semantic memory is our ability to recall facts and information about the world around us, while episodic memory allows us to remember details about life events, such as the people we were with and where we were at the time.

Young children do remember facts in the moment, such as who their parents are, or that they must say "please" before mom will give them candy. These are examples of semantic memory.

Related: How accurate are our first childhood memories?

However, when it comes to episodic memory, the lines become a bit blurred.

A prevailing scientific theory is that we tend to forget episodic memories that are formed between age 2 and 4 because the region of the brain that forms and retrieves them — the hippocampus — is not fully matured by this point.

Kids may fail to record specific episodes until age 2 to 4 because that's when the hippocampus starts tying fragments of information together, Nora Newcombe, a professor of psychology at Temple University in Philadelphia, told Live Science.

Newcombe said that, for children younger than that age range, episodic memory may be unnecessarily complex at a time when a child is just learning how the world works.

"I think the primary goal of the first two years is to acquire semantic knowledge, and from that point of view, episodic memory might actually be a distraction," Newcombe said.

However, recent research is beginning to turn this theory on its head. For instance, a study published in March 2025 in the journal Science revealed that in the first couple of years of life, the hippocampus can encode information that is required for episodic memory.

In the study, researchers showed 26 children age 4 months to 2 years a selection of images for two seconds each; the images were of faces, scenes and objects that form the bedrock of episodic memories. At the same time, the team analyzed activity in the children's hippocampi, using functional magnetic resonance imaging (fMRI).

Following a brief pause, the children were shown an image they'd previously seen, next to a new image, for four seconds. During this time, the researchers also monitored how long the kids looked at each image — another gauge of whether they recognized the old image after looking at the new one.

Overall, the researchers discovered that the greater the activity in the hippocampi, the longer the children spent looking at an image when it reappeared. The area within the hippocampus where brain activity was the strongest was also the region that is most associated with episodic memory in adults, the researchers found.

The findings of the Science study suggest that we experience infantile amnesia not because we don't retain information as young children but because we're unable to retrieve these memories as adults.

Along that vein, a 2023 study published in the journal Science Advances found that "forgotten" childhood memories could be reinstated in adult mice by using light to stimulate neural pathways that are relevant to specific memories.

The authors of the study first set out to explore developmental factors that could influence infantile amnesia. They found that mice with characteristics of autism were able to recall memories from their pup days.

Autism has many causes, but it has been previously linked to the overactivation of the mother's immune system during pregnancy. So, to make mice with an autism-like condition, the researchers stimulated the immune system of female mice during pregnancy.

This immune activation helped prevent the loss of early memories in these offspring by influencing the size and plasticity of specialist memory cells in their brains. When these cells were optically stimulated in adult mice without autism, their forgotten memories could be restored.

"These new findings suggest that immune activation during pregnancy results in an altered brain state that alters our innate, yet reversible 'forgetting switches' that determine whether the forgetting of infant memories will occur," study co-author Tomás Ryan, an associate professor of biochemistry at Trinity College Dublin, said in a statement.

Although the research was in mice and has yet to be studied in humans, it "holds significant implications for enhancing our comprehension of memory and forgetting across child development, as well as overall cognitive flexibility in the context of autism," Ryan said.

Editor's note: This story was originally published on Feb. 7, 2011, and was updated on Nov. 27, 2023 and March 26, 2025, to include the Science Advances study and the Science study, respectively.