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Most adults can summon a first childhood memory, but it usually comes from no earlier than preschool. The blank stretch before that is known as infantile amnesia. It appears in college students and grandparents alike, which suggests that it is not simply the ordinary fading that affects all memories over time. The puzzle is stranger: babies plainly learn about people, objects and language, yet adults cannot consciously revisit events from their own infancy.

Psychologist Nick Turk-Browne describes new evidence that separates the ability to form a memory from the ability to retrieve it years later. Brain scans show that the hippocampus can encode specific experiences by about one year of age. The findings weaken the idea that infancy is entirely “prememory” and shift attention toward a harder question: what happens to those early traces as the mind develops?

Two Explanations for the Missing Years

The hippocampus, a structure deep in the brain, is central to episodic memory, the memory of particular events. Because it develops substantially throughout childhood, one longstanding explanation for infantile amnesia is that babies cannot yet store such memories. On this view, the earliest years resemble the experience of adults with severe hippocampal damage: events occur, but they do not become durable records that can later be recalled.

The competing explanation is that infants do store memories but eventually lose access to them. Animal research supports this possibility. In mice, neurons active during an early experience can preserve a memory that later seems forgotten; stimulating those neurons can make the memory accessible again. That does not prove that human infant memories survive intact into adulthood, but it shows that apparent forgetting need not mean that the brain failed to encode an event.

Testing the question in humans has been unusually difficult. Functional magnetic resonance imaging can measure activity in the hippocampus safely, but awake babies move, lose interest and cannot follow instructions to keep still. Most infant fMRI research therefore takes place while babies sleep, when researchers cannot study the encoding of ordinary waking experiences. Turk-Browne’s laboratory spent more than a decade and over 400 scanning sessions developing ways to keep infants comfortable, engaged and sufficiently still.

Watching a Memory Form

In the resulting experiment, infants viewed photographs of faces, objects and scenes one at a time while undergoing fMRI. Soon afterward, each familiar image appeared beside a new image of the same kind. The researchers treated a longer look at the familiar photograph as evidence that the infant remembered it, then returned to the earlier brain scans to ask what had happened when that image first appeared.

The hippocampus had been more active for pictures the babies later seemed to recognize than for pictures they did not. The relationship was clearest in infants older than 12 months, in babies who showed stronger memory overall, and in the hippocampal subregion most closely associated with specific-event memory in adults. A brief experience, in other words, left a measurable neural signature that predicted behavior minutes later.

This result supports memory formation in infancy, but its limits matter. Looking time is an indirect measure rather than a verbal report. The experiment tested recognition after only a short delay, whereas infantile amnesia unfolds over years. And recognizing a single photograph is simpler than remembering an episode involving people, places, actions and a sense of oneself moving through time. The study shows that an essential memory system is working; it does not show that adults carry complete, recoverable recordings of infancy.

The Mystery Moves from Storage to Access

If the brain can encode experiences around age one, why do autobiographical memories usually begin at age four or five? Early traces may weaken, be reorganized as the hippocampus matures, or become difficult to retrieve once language and the sense of self change. A memory formed before a child can narrate experience may persist in a form that the later mind cannot easily search or interpret. The article leaves these possibilities open.

Answering them could illuminate more than childhood recollection. Early memory supports language learning and education, and disruptions in memory development may offer clues to developmental disorders. Understanding why stored experiences become inaccessible could also inform research on normal aging and diseases such as Alzheimer’s.

The study’s central lesson is therefore modest but consequential. Infantile amnesia is probably not an empty beginning in which nothing was recorded. Babies’ brains are already building memories; what remains mysterious is how those records change, whether any endure, and why the adults those babies become can no longer find them.