Why can’t we remember our early years? Do babies make memories at all?

Have you ever been convinced that you remember being a baby? A moment in a crib, or the taste of a first birthday cake?

Chances are, those memories aren’t real. Decades of research suggest that most people cannot recall personal experiences from the first few years of life.

However, even though we can’t remember being a baby, a new study has found new evidence that babies do take in the world around them and may also begin forming memories far earlier than once thought.

How did the study work and what did it find?

A study published this month in Science by researchers at Yale and Columbia universities has revealed that babies as young as 12 months old can form memories via the hippocampus – a part of the brain that stores memories in adults, too.

To observe this, the researchers used a specially adapted brain scan for infants during a single session. It allowed them to watch how babies’ brains responded while they were awake and looking at images of faces and objects. Parents remained close to their babies, which helped keep them calm and alert.

In the study, 26 infants aged four to 25 months were shown a series of images. It was found that if a baby’s hippocampus was more active the first time they saw a particular image, they would look at the same image for longer when it reappeared a short time later, next to a new one – suggesting they recognised it.

“Our results suggest that babies’ brains have the capacity for forming memories – but how long-lasting these memories are is still an open question,” said Tristan Yates, a postdoctoral research scientist in the department of psychology at Columbia University and lead author of the study.

This is the first time scientists have directly observed how a memory begins to take shape in an awake baby’s brain. Previous research relied on indirect observations, such as watching whether babies reacted to something familiar. This time, however, researchers observed brain activity linked to specific memories as they form in real time.

Most past brain activity studies have been done while babies were asleep, which limited what researchers could learn about conscious memory-building.

What does this tell us about early life memories?

The findings suggest that episodic memory – the kind of memory that helps us remember specific events and the context in which they took place – begins to develop earlier than scientists previously believed.

Until recently, it was widely believed that this type of memory didn’t begin to form until well after a baby’s first birthday, typically around 18 to 24 months. Although the findings from the Science study were strongest in infants older than 12 months, the results were observed in much younger babies as well.

So, at what age do we start making memories?

It is now understood that babies begin forming limited types of memory when they are as young as two or three months. These include implicit memories (such as motor skills) and statistical learning, which helps infants detect patterns in language, faces and routines.

However, episodic memory, which allows us to recall specific events as well as where and when they occurred, takes longer to develop and requires the maturation of the hippocampus.

According to Cristina Maria Alberini, professor of neural science at New York University, the period in infancy when the hippocampus is developing its ability to form and store memories may be “critical”. This window could be important not only for memory but also has “great implications for mental health and memory or cognitive disorders”, she added.

Memories formed in early childhood do not typically last very long, it is believed, which might explain why we can’t remember them later in life. In an ongoing study at the Max Planck Institute for Human Development in Germany, 20-month-old toddlers were able to remember which toy was in which room for up to six months, while younger children retained the memory for only about one month.

Why can’t we remember anything from infancy?

Humans’ near-universal inability to recall personal experiences from before the age of about three is a phenomenon known as “infantile amnesia”.

For decades, scientists believed this happens simply because babies’ brains were too immature to store episodic memories.

But the Science study has shown that babies do indeed form memories. The mystery is why those memories become inaccessible as we grow older.

One explanation, scientists say, is that babies’ brains undergo rapid neurogenesis – the fast-paced creation of new neurons in the brain. This rapid growth might disrupt or “write over” existing memories. In animal studies, when scientists slowed this process in baby mice, the mice were able to retain memories much longer – similar to adult mice.

There is also a hypothesis that episodic memory requires language to describe them and a “sense of self” to relate to them. Since these skills don’t fully develop until around age three or four, the brain might not yet have the tools to organise and retrieve memories in the way adults do.

Some researchers also think the process of forgetting might serve a developmental purpose. By letting go of specific early experiences, the brain might be better able to focus on building general knowledge – to understand how the world works, for example – without being distracted by detailed memories which no longer serve a purpose.

Can some people remember events from infancy?

Some people claim they can remember being a baby, but there is no evidence that what they describe are genuine episodic memories.

According to the Yale and Columbia study, this belief typically stems from a psychological process called “source misattribution”.

People may remember information, such as that they cried during their first haircut, but not where that information came from. They might unconsciously attribute the memory to personal experience when it actually came from a photo, family stories or a parent’s retelling. Over time, the line between “real” and “reconstructed” has blurred.

Research shows that early family stories, frequent photo viewings or cultural emphasis on early development can all contribute to this phenomenon.

Yale is currently conducting a new study in which parents will film their babies regularly, either with their phones angled from the baby’s point of view or by using head-mounted cameras on toddlers. Later, as the children grow older, the researchers will show the children these old videos to see if they recognise the experiences, primarily by monitoring brain activity, to find out how long early memories can last, Yates told Al Jazeera.

Could early memories be recalled later in life?

There is debate about whether early life memories are completely erased or have simply become inaccessible and could eventually be recovered.

Yates said that while the latest study does not answer this question, preliminary evidence from other research at the Yale lab shows that early life memories can be recalled in early childhood, but not later childhood.

“I think the idea that at least some of our early life memories may exist in some form in our brains as adults is fascinating,” she said.

Studies of adult rodents have shown that early memories can be brought back through approaches such as optogenetics – activating the specific brain cells which are believed to store those memories. This works by identifying the brain cells involved in forming a memory, then later using light to reactivate those same cells, causing the animal to recall the memory.

Techniques such as optogenetics cannot yet be used in humans, but the study of rodents suggests that the process by which we retrieve memories is where the issue lies, rather than whether the memories exist at all, according to Paul Frankland, senior scientist at The Hospital for Sick Children in Toronto.

“Perhaps there are natural conditions where these early life memories become more accessible,” he added.

Psychoanalysts such as Sigmund Freud believed that early childhood memories are not lost but buried deep in the unconscious, and that psychotherapy might help bring them to the surface by changing mental states.

However, Frankland said that this is a “controversial area” as “it is difficult to verify the veracity of recovered memories”.