When my daughter saw a bumblebee in our garden around the time of her second birthday, she surprised me by talking about being stung by a wasp the summer before, or half her life earlier.

Although her memory of the intense pain of a sting wasn’t so unexpected, she brought up details I had forgotten, including the fact that we put frozen peas on the welt and that she got a cupcake afterward.

How was it, I wondered, that my daughter at age 2 had the ability to recollect with such precision something that occurred so far back in her short life, while most of us can’t remember much of anything before the age of 4?

Like any first-time parent, I have been amazed by how quickly my daughter has transformed from a defenseless newborn to an opinionated little person in the space of a few years. By the time she was 2½, I could see every day the new ways in which she was building a detailed picture of the world around her, the people and things that were important to her.

For me, her developmental milestones offered an opportunity of a different sort: the chance to gain new understanding about a forgotten event that had nevertheless loomed large in my own life.

I was 2½ when my father died. He was 28 when his car was hit by a drunk driver. He never regained consciousness and died a few days later. When I was growing up, I sometimes told people that I hadn’t known him. Because I couldn’t remember anything about the time before the accident, it seemed like the most straightforward answer.

More than grief, I experienced a sense of disconnection from an experience that seemed central to my life. When I was young and relatives talked to my older brother and me about it, wanting to share who our father was and express their own sense of loss, I often felt confused and distressed.

Now, as my daughter reached the exact age I was when that event occurred, I hoped to answer questions about her, and me. What do young children know about those close to them, and why is it that those early moments and relationships, as significant as they may be, slip away into the haze of forgetting? If I didn’t remember my dad, did that mean I hadn’t really experienced his sudden absence?

I began trying to educate myself about children’s capacity to form and retain memories and why, it seems, at some point a curtain is drawn across our early recollections.

It was around the turn of the 20th century when scientists coined the term childhood or infantile amnesia. The precise age when the veil of infantile amnesia descends is a subject of ongoing debate, in part because only limited studies have been done involving children. But according to Emory University memory scientist Patricia Bauer, the average age for an earliest memory among Western cultures is 3 to 3½. And until about age 7, memories are much spottier than they are in later childhood and adulthood.

Compounding the puzzle, as Bauer writes, is the fact that “within the period eventually obscured by childhood amnesia, children had remarkably rich autobiographies.” So what happens to make us forget?

Research is still being done to better understand the nuances of this seeming contradiction. Although various hypotheses have been put forward — including the notion that language development is a precursor to memory retention, meaning that because young children lack a full vocabulary, they cannot preserve memories — scientists are increasingly focused on the dramatic changes that occur to the brain during early childhood.

One theory is that the rapid development during early childhood of new neurons in the hippocampus region of the brain, which is associated with memory and learning, interferes with memory retention, potentially by replacing synapses that are linked to specific memories.

The instability associated with that rapid neuron growth and replacement, known as “neurogenesis,” means a decreased probability of being able to retrieve any single memory, said Paul Frankland, a senior scientist at the Hospital for Sick Children in Toronto. The chances that an adult can retrieve a particular memory from age 3, for example, are very low, somewhat higher for a memory from age 5, and higher still for memories made as age increases and neurogenesis slows, scientists believe. That pattern of increasingly probable memory retrieval tracks with observations of children.

Frankland and his colleagues have conducted experiments on rodents that support this theory. First, the scientists taught adult mice, which have a lower rate of neurogenesis, similar to an adult human brain, to navigate a maze. They then artificially increased the mice’s rate of hippocampal neurogenesis. The mice became more likely to forget what they had learned about the maze, suggesting what Frankland characterizes as “rewiring” overwriting the recollections. The converse was true with young mice, which, like human children, have higher rates of neurogenesis and would be more prone to forgetting what they learned about the maze. When the scientists artificially slowed the young mice’s neural development, they were more likely to remember their way through the maze.

Interestingly, guinea pigs, which are born with much more developed brains (they can walk and see much earlier) do not naturally exhibit the same kind of infantile amnesia that mice do. But when researchers boosted their neurogenesis in experiments, they did.

So what is a parent to conclude from all this? Researchers seem to agree that as children’s ability to retain memories emerges, their ability to recall particular events is increased when adults talk to them about what they experienced after the fact.

Most often, people’s earliest memories involve highly emotive events, which Frankland said could be linked to the possibility those events are associated with greater strengthening of the neural connections where memories are stored. That means those memorable events could even overcome the effects of neurogenesis.

And while we can’t recall most early events, they do appear to shape us in ways that remain poorly understood.

“The wrong takeaway is that it doesn’t really matter what your kids experience, because they’re going to forget it anyway,” he said.

Carole Peterson, a researcher at Memorial University of Newfoundland, said early experiences can have a lasting impact on behavioral reactions and attitudes. For example, someone may not remember an early negative experience with a dog but might still respond later with fear. The same could be true for children subject to early abuse or deprivation.

For parents, the notion that the impact of painful events can transcend children’s memories is unsettling. But the converse idea is a hopeful one: that the acts of love we show our young children every day, though they will eventually be lost to childhood amnesia, leave an enduring mark.

After my father’s death, our large extended family rallied around my mom, brother and me, pitching in with child care so she could attend graduate school. I don’t remember a lot of it, but that support shaped my view of how people show up for one another.

My mother’s efforts to juggle a career with solo parenting gave me a sense of professional empowerment. Her eventual remarriage taught me about resilience and moving on after loss. Those are the lessons I’m choosing to embrace as I raise my daughter.

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