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The Great Forgetting

The mechanics of memory remain mysterious – but new infant studies could hold the key.

The Great Forgetting
Reader's Digest

I’m the youngest by far of five children. By the time I started first grade, my siblings were gone, and we went from being 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 oldest 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 earliest 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 again 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 said, ‘No, that never happened to me,’” 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 very 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 donkeys, he recalled a moment not long after the trip when a woman had given him lots of cookies.

Peterson has no idea why he would remember that – it was an unremarkable moment that the family hadn’t reinforced with chitchat. 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 cookies, 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, smells, tastes and tactile sensations of experience – arrive and register across the cerebral cortex, the seat of cognition. For these to become memory, they must undergo bundling in the hippocampus, a brain structure located under the cerebral cortex. But some parts of the hippocampus aren’t fully developed until adolescence, making it hard for a child’s brain to complete this process.

“So much has to happen biologically to store a memory,” psychologist Patricia Bauer of Emory University told me. There’s “a race to get it stabilised and consolidated before you forget it. It’s like making Jell-O: you mix the stuff up, you put it in a mould, and you put it in the refrigerator to set. But your mould has a tiny hole in it. You just hope your Jell-O – your memory – gets set before it leaks out through that tiny hole.”

In addition, 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, Professor Qi Wang from Cornell University and Yubo Hou, an associate professor from Peking University, 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 prize individuality less than North Americans and thus may be less likely to draw attention to the moments of an individual’s life. Westerners, by contrast, reinforce recollection and keep the synapses that underlie early personal memories vibrant.

When an adult engages a child in a lively conversation about events, inviting him or her to add to the story, “that kind of interaction contributes to the richness of memory over a long period of time,” Bauer said. “The child learns how to have memories and how to tell the story.”

Our first three to four years are the maddeningly, 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 – whether abuse or exuberant cherishing – 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. “You can’t remember going ice-skating with Uncle Henry, but you understand that skating and visiting relatives are fun,” Bauer explained. “You have a feeling for how nice people are, how reliable they are. You might never be able to pinpoint how you learned that, but it’s just something you know.”

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.

AEON (July 30, 2014), © 2014 by AEON Media Group LTD., aeon.co.



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