Yale Scientists Explain Why We Forget Infancy: Memories Stay, Retrieval Fails
A groundbreaking study from Yale University, published in the journal Science in March 2025, reveals that infants are capable of forming episodic memories much earlier than previously believed. Researchers demonstrated that babies as young as four months show signs of memory encoding in the hippocampus β a brain region responsible for memoryβchallenging the long-standing theory that early childhood amnesia results solely from an underdeveloped memory system. Instead, the study suggests that these early memories are stored but later become inaccessible.
Inside the Study: How Scientists Uncovered Early Memory Formation
Research Team and Publication
According to Science Daily, the research was led by Tristan Yates, then a Yale graduate student and now a postdoctoral researcher at Columbia University, under the supervision of Nick Turk-Browne, Professor of Psychology at Yale and Director of Yale’s Wu Tsai Institute. Their work was published in the prestigious journal Science.
This study stands out due to its use of advanced functional magnetic resonance imaging (fMRI) techniques specially adapted for infants β a notoriously challenging group for neuroimaging studies. The project builds on a decade of efforts by Turk-Browneβs lab to decode infant brain activity while awake and engaged.
Study Design and Methodology
To investigate how and when infants form memories, the Yale research team designed a controlled experiment involving 26 infants aged between 4 months and 2 years. The study combined behavioral observation with advanced brain imaging β a rare approach in infant research due to the challenges of scanning awake babies.
Each infant was placed in a specially adapted functional magnetic resonance imaging (fMRI) scanner designed to accommodate their size and short attention spans. During the scan, researchers showed the babies a series of unfamiliar images, including faces, objects, and natural scenes, while monitoring activity in their hippocampus β the brainβs memory center.
After viewing several images, the infants were tested for memory recognition. Pairs of images were displayed β one the child had seen earlier and one entirely new. Researchers measured how long the infants looked at each image, a well-established method in developmental psychology where longer gaze times indicate recognition.
Crucially, the team focused on the posterior hippocampus, the region associated with episodic memory in adults. They found that the stronger the hippocampal response when the infant first saw an image, the more likely the infant was to focus on it during the recognition test. This provided direct evidence of memory encoding in real-time.
The study also built on a decade of work by Yaleβs lab developing techniques to capture high-quality brain imaging data from awake infants β an advancement that allowed researchers to go beyond behavioral observations and measure neural activity directly.
Researchers note that such a combination of neuroimaging and behavioral testing in infants is rare and sets this study apart from previous work that relied heavily on indirect measures or animal models.
Comparison with Previous Research
Prior studies have struggled to measure memory in pre-verbal infants because traditional methods rely on verbal recall. Most assumed that the hippocampus was too immature in infancy to support episodic memories, leading to the concept of infantile amnesia β the inability to recall memories from early childhood.
Earlier research by Turk-Browne’s team had shown that infants could engage in statistical learning, recognizing patterns in data, which uses a different hippocampal pathway. However, no conclusive evidence existed to show episodic memory formation before this study.
What Makes This Study Innovative?
Unlike prior research that largely focused on observable behaviors or required verbal confirmation, this study provided direct neuroimaging evidence of memory encoding in the infant hippocampus. It is the first to:
- Successfully link hippocampal activity with later memory recall in awake infants.
- Distinguish between two types of memoryβepisodic and statisticalβat the neural level in babies.
- Demonstrate that episodic memory encoding begins earlier than the verbal recollection phase.
This challenges the long-held belief that young children cannot form episodic memories due to biological immaturity, suggesting instead that these memories may be inaccessible rather than absent.
Five Key Conclusions of the Study
1. Babies Can Form Episodic Memories Before They Can Speak
Neuroimaging showed that even four-month-old infants demonstrated hippocampal activation when seeing new images, meaning the brain was already processing and storing the event.
Example: A baby seeing their grandmotherβs face for the first time might encode this experience, even if they cannot express or recall it later.
2. Stronger Hippocampal Activity Predicts Better Memory Recall
The study found a direct correlation: the more active the hippocampus during the first exposure, the more likely the baby was to remember the image.
Example: A baby who paid close attention to a colorful toy may later recognize it instantly when seeing it again.
3. Posterior Hippocampus β Key to Episodic Memory β Is Active in Infants
This mirrors memory processing in adults, confirming that the brainβs episodic memory system is functioning earlier than previously believed.
Example: An infant might form a detailed memory of playing in a park, though retrieving it years later remains unlikely.
4. Statistical and Episodic Memories Develop Along Separate Timelines
While statistical learning appears earlier, this study shows that episodic memory starts developing well within the first year of life.
Example: A baby quickly learns that every bath ends with a towel (statistical learning), but can also remember specific bath-time moments (episodic memory).
5. Early Memories Might Persist but Become Inaccessible
The research suggests that infantile amnesia may stem from retrieval issues, not memory absence. Memories could remain stored but unreachable later.
Example: Adults may have no conscious recollection of their first birthday, but the memory might exist deep in the brain.
How Memory Formation Relates to Cognitive Abilities
The ability to form episodic memories early in life has significant implications for understanding cognitive development. Episodic memory β remembering specific events β is crucial for learning, social bonding, and decision-making. This early memory capacity may support:
- Language Acquisition: By recalling word-object associations.
- Emotional Development: Remembering comforting experiences strengthens bonds with caregivers.
- Problem-Solving: Drawing from past events helps infants predict outcomes.
Recognizing this early function of the hippocampus deepens our understanding of how children process and learn from their environment long before they can articulate experiences.
Wider Impact: Why the Findings Matter for Science, Medicine, and Society
The findings carry significant implications far beyond understanding memory formation in infants. For neuroscience, the study challenges long-standing assumptions about brain development and provides new insights into how the hippocampus functions from the earliest stages of life. It opens the door for further research into how early memories are storedβand why they become inaccessible over time.
In medicine, the ability to measure memory encoding in infants could offer new tools for detecting developmental delays or early signs of neurological disorders. Understanding memory pathways from infancy may help refine diagnostic approaches for conditions like autism or learning disabilities, where memory and information processing play a crucial role.
For educators and child development specialists, the study reinforces the importance of early experiences. If babies encode specific memories much earlier than previously believed, enriching environments and positive interactions in the first years of life may have a lasting impact, even if those memories remain out of conscious reach later.
The research also reshapes how society views infancy. It challenges the common assumption that what happens in the first years of life is simply forgotten, highlighting instead that these early moments may shape cognitive and emotional development in ways science is only beginning to understand.
Conclusions: Rethinking Infantile Amnesia
The Yale study challenges the long-standing belief that we cannot form memories in infancy due to an underdeveloped hippocampus. Instead, it provides compelling evidence that infants encode episodic memories much earlier than previously thought, though these memories become inaccessible over time.
Future research may uncover ways to retrieve these early memories or explain why they fade from conscious recall. For now, the study sends a clear message: early experiences matter, and babies remember more than we realizeβeven if those memories remain beyond our reach as adults.
This growing understanding of memory formation also draws attention to the importance of noticing how babies respond to their environment from the earliest months. Apps like BabyBright give parents simple tools to engage with their child and observe how they react to age-appropriate activities. Such interaction can help parents better follow their babyβs development and understand how they explore and process the world around them.
