Why can't we remember being babies?

I’m the youngest by far of five children. By the time I was six, my siblings were gone, and we went from a very noisy household to a very quiet one. My family has told me stories about those early years before my siblings left. How my brother ambushed me around corners with a toy crocodile. How my eldest sister carried me like a kangaroo with her joey. But I can offer very few stories of my own from that time.

Hardly any adult can. There is a term for this—infantile ­amnesia, coined by Sigmund Freud to describe the lack of recall adults have of their first three or four years and their paucity of solid memories until around age seven. There has been a century of research about whether memories of these early years are tucked away in some part of our brains and need only a cue to be recovered. But research now suggests that the memories we form in these early years simply disappear.

Psychologist Carole Peterson of Memorial University of Newfoundland has conducted a series of studies to pinpoint the age at which these memories vanish. First, she and her colleagues assembled a group of children between the ages of four and 13 to describe their early recollections. The children’s parents stood by to verify the memories, and even the youngest kids could recall events from when they were around two years old. The children were interviewed two years later. Nearly 90 per cent of the memories initially offered by those ten and older were retained. But the younger children had gone blank. “Even when we prompted them about their earlier memories, they insisted, ‘No, that never happened,’” Peterson said. “We were watching childhood amnesia in action.”

In both children and adults, memory is bizarrely selective about what adheres and what falls away. In one of her papers, Peterson tells a story about her own son. When he was 20 months old, she had taken him to Greece, where he became excited about some donkeys. They discussed the donkeys for at least a year.

But by the time her son went to school, he had completely forgotten about them. He was queried when he was a teenager about his earliest childhood memory. Instead of the Greek donkeys, he recalled a moment not long after the trip when a woman had given him lots of biscuits.

Peterson has no idea why he would remember that—it was an unremarkable moment that the family hadn’t reinforced with chit-chat. To get a handle on why some memories endure over others, she and her colleagues studied the children’s memories again. They concluded that if a memory was very emotional, children were three times more likely to retain it.

Dense memories—in which the kids understood the who, what, when, where, and why—were five times more likely to be retained than disconnected fragments. Still, oddball and inconsequential memories, such as a bounty of biscuits, will hang on, frustrating the person who wants a more penetrating look at his or her early past.

To form long-term memories, an array of biological and psychological stars must align. The raw materials of ­memory—the sights, sounds, tastes—arrive and register across the cerebral cortex, the seat of cognition.

For these to become memory, they must undergo bundling in the hippocampus. But some parts of the hippocampus aren’t fully developed until adolescence, making it hard for a child’s brain to complete this process.

Young children have a tenuous grip on chronology. They don’t have the vocabulary to describe an event, so they can’t create the kind of causal narrative that Peterson found at the root of a solid memory. And they don’t have a great sense of self, which would encourage them to think about their experiences as part of a life narrative.

Plus, in our early years, we create a storm of new neurons in the hippocampus. A recent study in mice suggests that this process, called neurogenesis, can actually create forgetting by disrupting the circuits for existing memories. Our memories can also become distorted by other people’s memories of the same event or by new information.

Of course, some people have more memories from early childhood than others do. A 2009 study conducted by Peterson and professors Qi Wang and Yubo Hou found that children in China have fewer of these memories than children in Canada do. The finding, they suggest, might be explained by culture: Chinese people prize individuality less than North Americans and thus may be less likely to draw attention to the moments of an individual’s life. Our first three to four years are the mysteriously blank opening pages to our story of self. During that time, we transition from what my brother-in-law calls “a loaf of bread with a nervous system” to sentient humans. If we can’t remember much from those years, does it matter what actually happened? If a tree fell in the forest of our early development and we didn’t have the cognitive tools to stash the event in memory, did it still help shape who we are? Bauer says yes. Even if we don’t remember early events, they leave an imprint on the way we understand and feel about ourselves, other people, and the greater world. We aren’t just the sum of our memories, or at least not entirely. We are also the story we construct about ourselves. And that’s a story that we will never forget. 

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