Sci-Fi or Science? Hidden Infant Memories Might Last Into Adulthood

Imagine being able to recall the sights, sounds and sensations from your earliest days – memories long thought lost to the fog of infancy.

A study from Yale University, published in Science, challenges the belief that infantile amnesia results from an inability to form memories. Instead, researchers found that infants as young as one year old can encode episodic memories, suggesting that these early experiences may linger in the brain.

The mystery of infantile amnesia

Whether it’s the first time we took a wobbly step or the sound of a parent’s voice soothing us to sleep, our earliest memories seem to be locked away, unreachable and seemingly erased. This phenomenon, known as infantile amnesia, has intrigued researchers since it was first described by Sigmund Freud more than a century ago.

The traditional explanation has long been that our brains simply aren’t equipped to form lasting memories during infancy. The hippocampus – the brain region responsible for encoding and storing episodic memories – is still maturing well into adolescence, so it was assumed that the ability to form memories only kicks in later. This theory gained support from research showing that the hippocampus continues to develop throughout childhood, forming new neural connections and increasing in volume. Some researchers proposed that the brain’s rapid development in infancy might actively “overwrite” early memories, much like new data being recorded over old files.

However, recent research has begun to challenge this idea, suggesting that the reality might be far more complex. Animal studies have shown that even infant brains can form memory traces. Experiments with rodents revealed that while infant mice could remember tasks they learned, they would “forget” these memories as they matured. However, those memories could be brought back with direct stimulation of the hippocampal neurons that were active during learning. This suggested that the memories were still there – just inaccessible.

This new perspective raises a tantalizing question: Are our early-life memories really gone forever, or are they simply buried somewhere within our brains, locked away behind inaccessible neural pathways? If the latter is true, could future advancements in neuroscience help us retrieve them?

Unfortunately, studying this phenomenon in humans has proved difficult in the past.

“The hallmark of these types of memories, which we call episodic memories, is that you can describe them to others, but that’s off the table when you’re dealing with pre-verbal infants,” said corresponding author Dr. Nick Turk-Browne, a professor of psychology and director of the Wu Tsai Institute at Yale University.

The new study set out to tackle this mystery. Instead of asking how memories are lost, it investigates whether they are ever really gone at all.

Are infant memories still there?

Turk-Browne and the team used functional magnetic resonance imaging  to measure brain activity in awake infants aged four months to two years. The study involved 26 infants, split evenly between those younger and older than 1 year of age.

Instead of relying on the infants’ verbal responses, which would be impossible with pre-verbal participants, the researchers employed a behavioral measure called the subsequent memory paradigm. The infants were first shown images of unfamiliar faces, objects or scenes. After a series of unrelated images, the infants were then presented with a pair of images: one they had previously seen and one they had not. The team measured the infants’ gaze patterns to determine whether they looked longer at the previously seen image, indicating recognition.

“When babies have seen something just once before, we expect them to look at it more when they see it again. So, in this task, if an infant stares at the previously seen image more than the new one next to it, that can be interpreted as the baby recognizing it as familiar,” said Turk-Browne.

Infants older than one year showed increased hippocampal activity during the initial viewing of an image that they later recognized. This hippocampal encoding effect was stronger in infants older than one year of age compared to those younger, suggesting that the ability to form episodic memories emerges around the end of the first year of life.

The team also found a clear subsequent memory effect – greater hippocampal activity during initial exposure was associated with a stronger memory trace, indicated by longer looking times when the image reappeared.

What if we could retrieve our earliest memories?

Turk-Browne and his team speculate that memories from infancy might still reside in the brain, but their retrieval becomes increasingly difficult as neural pathways change.

One reason for this inaccessibility could lie in the different forms of learning and memory that emerge in early life. The Yale team had previously demonstrated that a different form of memory called statistical learning – the ability to detect patterns in the environment – appears earlier than episodic memory.

“Statistical learning is about extracting the structure in the world around us. This is critical for the development of language, vision, concepts and more. So, it’s understandable why statistical learning may come into play earlier than episodic memory,” said Turk-Browne.

His team is already taking steps to explore the possibility of unlocking these hidden memories. One of their ongoing projects involves examining whether toddlers and preschoolers can recall memories from videos taken from their perspective as infants. Early results are promising, suggesting that some memories from infancy may persist until preschool age before fading.

“Tristan’s [the first author of the study] work in humans is remarkably compatible with recent animal evidence that infantile amnesia is a retrieval problem. We’re working to track the durability of hippocampal memories across childhood and even beginning to entertain the radical, almost sci-fi possibility that they may endure in some form into adulthood, despite being inaccessible,” said Turk-Browne.

The question of whether early memories are truly gone or just deeply buried remains unanswered. But as neuroscientists continue to probe the intricacies of memory formation and retrieval, one thing is certain: the boundaries between science and science fiction are becoming increasingly blurred.

Reference: Yates TS, Fel J, Choi D, et al. Hippocampal encoding of memories in human infants. Science. 2025. doi: 10.1126/science.adt7570

This article is a rework of a press release issued by Yale University. Material has been edited for length and content.