A new Memorial-based study is the first to systematically mark the onset of "childhood amnesia" in children rather than adults. The research shows that by our tenth birthday our early pre-school memories have receded into an inaccessible past.

It's a result, the lead researcher says, that further deepens the mystery around the fate of our earliest autobiographical memories.

"I expected that they would differ, but there's a striking similarity in the age of the earliest memory for adults and ten-year-olds," says Dr. Carole Peterson, a psychologist at Memorial University of Newfoundland. Her study, funded by NSERC, was published in the August issue of the journal Memory.

The results extend what Dr. Peterson calls the paradox of surrounding childhood amnesia – adults’ inability to recall autobiographical events that occurred before the age of four. Four- and three-year-olds can readily recall events from their second year. Yet, by the age of ten these earliest memories have receded behind what's been dubbed the "reminiscence bump."

"We don't have any good models to explain this. The memories were there and had been verbally accessible. So, why aren't they there any more?" says Dr. Peterson, who since the 1970s has explored the dynamics of children's autobiographical memories.

For this study, Dr. Peterson and undergraduate students Valerie Grant and Lesley Boland asked 136 participants ages six to 19 for their earliest memories. It's a sample size that Dr. Peterson says provides statistically significant results.

The researchers found that six- to nine-year-olds recalled earlier events (from when they were about three) than did older children. However, there were no differences in the age of earliest memory among the older groups. Their earliest memories were from about three and a half years of age. Thus, by ten years old, participants’ memories had entered an "adult" state of remembering.

So what are our earliest memories?

While previous researchers have found that a large number of adults' earliest memories are emotion laden, Dr. Peterson's group "found that the majority of the early memories were about relatively mundane experiences." These ranged from the memory of looking at a flower growing out of a crack in the pavement to walking across a narrow bridge over a river. Only teenaged girls 14 to 19 had a preponderance (about 40 per cent) of negative first memories.

"It's not at all clear why some things get into long-term memory and some do not," says Dr. Peterson.

The researchers also found few differences between age groups in how earliest events are remembered. All of the participants recalled events with about the same level of narrative complexity, generally describing a "snapshot of a moment in time."

"Perhaps it’s the level of narrative skill possessed at the age at which the memory was encoded, not the current narrative skill, that determines the structure of a recollection," write the authors.

The research is part of Dr. Peterson's larger, ongoing research on children's autobiographical memories. The present findings have prompted a collaborative study exploring the earliest memories of autistic children to determine the role of self-awareness – one possible factor put forward by some researchers – in determining the onset of childhood amnesia. Autistic children are thought to lack a strong sense of self.

While the bulk of our pre-school memories will surely slip over the memory threshold, Dr. Peterson says that parents can play a role in determining which of their children's memories become lifelong ones. The more parents talk to children about particular experiences, the greater the chance that this verbal reinforcement will extend early memories.

"Talking a lot about your experiences, encoding them in language, has an impact on preserving the memory, there's no doubt about that," says Dr. Peterson. "But this doesn't solve the mystery of why it is that something that you could remember and talk about at one stage, disappears later."

Memorial University of Newfoundland
4 October 2005