Early Sensory Memory Development Research

Short answer: Infants form real, specific memories long before they can speak. What we call infantile amnesia is a retrieval problem rather than an encoding problem: early memories are stored through sensory and emotional channels, particularly smell and sound, and become hard to reach once the brain reorganises around language. For parents, the practical implication is that the sensory environment of the first years, its smells, sounds, routines and predictability, is doing more memory work than any vocabulary drill.

Do babies form memories before they can talk?

Yes. Contemporary neuroscience and developmental psychology no longer support the classical view that early childhood is defined by an absence of episodic memory formation.

For much of the twentieth century, dominant theories derived from Freud and Piaget argued that the first three to four years of life were marked by "infantile amnesia," a period during which the hippocampus and prefrontal cortex were assumed to be functionally immature. Infants could acquire habits and skills, the argument went, but were biologically incapable of forming event-specific memories, which could only emerge once language enabled narrative encoding.

That deficit model has been overturned. Neuroimaging of awake infants, combined with longitudinal behavioural studies, shows that the limitation in early memory is not encoding capacity but encoding modality and later retrieval. Children under five have a functioning episodic memory system that operates through sensory and affective channels rather than verbal narrative.

What is a "core memory" in a child who cannot speak?

In early childhood, a core memory is a specific, emotionally weighted representation of a past event that influences later behaviour, whether or not it can ever be described in words.

In the adult brain, episodic memory is defined by conscious recall of time, place and narrative context. In infants that definition has to adapt. Early core memories are specific in time and place and emotionally encoded, but not linguistically indexed, so their persistence shows up in behaviour, neural activation and later affective responses rather than in verbal report.

Two learning systems run in parallel in the infant brain:

• Statistical learning, which extracts regularities from repeated exposure, such as category formation and language patterns.

• Episodic memory, which encodes a single, distinct event tied to a particular context.

Statistical learning engages the anterior hippocampus from as early as three months of age, and the posterior hippocampus, which supports episodic encoding in adults, becomes functionally active by the end of the first year. The neural substrate for core memory formation is therefore operational well before fluent speech.

What does the brain scan evidence actually show?

A 2025 study using fMRI in awake infants between four months and two years of age found a direct relationship between hippocampal activation during encoding and later recognition behaviour. Its key findings:

• Anterior hippocampal activation in infants younger than twelve months during pattern-based learning.

• Posterior hippocampal activation in infants older than twelve months during encoding of specific stimuli.

• A significant correlation between encoding-related hippocampal activity and later recognition, strongest in the posterior hippocampus.

By roughly twelve months, the infant brain shows the same functional hippocampal signature associated with episodic memory in adults, which means preferential looking reflects retrieval of a stored trace rather than reflexive attention.

Why can't adults remember being a baby?

Early childhood amnesia reflects a failure of access, not a failure of encoding. During early development, high rates of hippocampal neurogenesis and cortical reorganisation alter retrieval pathways, so memories encoded through sensory and affective keys become inaccessible once the brain shifts toward language-based indexing.

The behavioural evidence fits. Young children can recall specific events from infancy when tested during early childhood, and access diminishes as linguistic and narrative systems come to dominate retrieval.

Why are emotional moments remembered more strongly?

Because early on, amygdala connectivity with the medial prefrontal cortex is positive rather than inhibitory, so emotional input amplifies hippocampal encoding instead of being dampened by it. Emotionally salient events are encoded with high fidelity, sensory features become tightly bound to affective states, and the memories are experienced as visceral rather than contextual.

Why does smell trigger the oldest memories?

Olfactory signals bypass the thalamus and project directly to the amygdala and entorhinal cortex, and the olfactory system is functional at birth while visual and semantic systems mature gradually. Neuroimaging of neonates shows differential cortical responses to pleasant and aversive odours within the first month, so odour-based encoding is available almost immediately.

Research comparing sensory triggers finds that odour-evoked memories peak in the first decade of life, while visual and verbal memory peaks arrive later, in adolescence or early adulthood, and that emotional intensity and the sense of being transported back are highest for olfactory cues. Studies of neonatal odour exposure show retention extending nearly two years, with infants exposed to specific odours during feeding recognising and preferring them as toddlers.

Infants also retrieve learned behaviours only when the original odour context is present, and retrieval fails when the cue is removed, which tells us early episodic memories are compound representations where event and sensory context are inseparable.

Does sound work the same way?

Auditory memory forms before birth and provides temporal continuity across early development. Fetuses in the third trimester encode auditory patterns that persist for weeks after birth, measurable in newborns through cardiac and attentional responses.

By six to seven months, infants retain musical structures over multi-week intervals, and they store them abstractly rather than as raw acoustic imprints, recognising melodies across changes in pitch and key. Neuroimaging of sleeping toddlers shows hippocampal reactivation of learned auditory material during sleep, with the strength of that reactivation predicting later recall, so sleep consolidates early auditory memories. This is one reason the 2-6 window rewards daily rhythm and music far beyond any musical outcome.

What behavioural proof exists that infants remember?

Deferred imitation. Infants as young as nine months reproduce novel actions after delays of twenty-four hours, by fourteen months retention extends to weeks and months, and by twenty months children retain complex action sequences for up to a year. Success rates in experimental groups far exceed baseline imitation, confirming stored representations rather than chance.

Around twelve to fourteen months, infants begin retrieving memories across changes in context, marking the emergence of flexible episodic memory that can generalise beyond the original sensory environment.

How does the sensory environment shape memory?

Multisensory binding increases memory persistence. Olfactory cues enhance visual processing in early infancy, guiding attention toward socially relevant stimuli such as caregivers, and reliance on olfactory scaffolding decreases as visual systems mature, a developmental handoff between sensory systems.

Predictability of sensory input also shapes hippocampal development, and environments characterised by chaotic or unpredictable sensory signals are associated with poorer memory outcomes years later. Routine, in other words, is not just a scheduling convenience.

A two-stage model of early memory

Stage 1: sensory-affective encoding, 0 to 18 months. Dominant systems are the amygdala, olfactory bulb and anterior hippocampus. Memory is rigid, context-bound and affective, and retrieval depends on sensory keys.

Stage 2: episodic-narrative encoding, 18 months to 5 years. Dominant systems are the posterior hippocampus and prefrontal cortex. Memory becomes flexible, declarative and increasingly decontextualised as language reorganises access.

Early memories are not erased. They are rendered inaccessible when the retrieval system changes.

What this means for parents

The under-five brain is not a blank slate but a high-fidelity recorder of sensory experience. Infants encode specific, emotionally meaningful events from the first year of life, scaffolded by smell and sound, consolidated through sleep, and shaped by emotional intensity.

Practically, that argues for consistent routines and predictable sensory environments, for real materials with real textures and smells rather than flat screens, for daily music and rhythm, and for protecting sleep, since consolidation happens there. For early childhood, the memory is not the story. It is the scent, the sound, and the emotional climate in which development unfolds.

Frequently asked questions

Can babies form memories? Yes. Neuroimaging shows the hippocampus encoding specific events well before language, with the adult-like posterior hippocampal signature present by around twelve months.

Why do we not remember our first years? The memories are encoded but become hard to access. Hippocampal neurogenesis and cortical reorganisation change retrieval pathways as language-based indexing takes over.

Why does smell bring back childhood memories so vividly? Olfactory signals reach the amygdala and entorhinal cortex directly, bypassing the thalamus, and odour-evoked memories peak in the first decade of life while visual and verbal memories peak later.

Do babies remember sounds from before birth? Third-trimester fetuses encode auditory patterns that persist for weeks after birth, detectable through newborn cardiac and attentional responses.

What can parents do with this? Keep routines predictable, favour real materials with texture and scent over screens, build daily music and rhythm into play, and protect sleep, which is when early memories consolidate.

Works cited

1. Yates et al., hippocampal encoding of memories in human infants, Science (2025), summarised at Columbia News.

2. Sensory experience in the newborn infant and its long-term retention: an experimental analysis of odour learning in human newborns, ResearchGate.