Psychologists Harlene Hayne and Gabrielle Simcock, who are researching the cause of childhood amnesia (the ability to remember events before ages two or three), have found children could only describe events from early childhood using the limited language they knew at the time.
"Our findings suggest it may be difficult, if not impossible, for adults to provide accurate verbal testimony about events that only occurred during this phase of their life," Hayne said.
The research was recently published in the American medical journal Psychological Science.
"If you take our data to their logical conclusion, then one implication would be that we need to express scepticism about very early verbal memories that are recovered during the course of therapy," she said.
But Hayne said because the research involved positive rather than negative memories and there was no trauma involved in the recollection, she was reluctant to apply the findings to instances of recovered memory for traumatic things like abuse.
Using a device call The Magic Shrinking Machine, Hayne and Simcock visited 80 children aged 27 to 39 months in their own homes during 2000 and 2001, and taught them to play a game with the device.
It was specially constructed for the project so none of the children had prior or subsequent experience with the machine.
Their language skills were also measured.
When questioned six months to one year later about the game all recalled the event, but none were able to use words to describe it that had not been part of their vocabulary at the time.
"In short, children's verbal memory for the event was frozen in time - it reflected their language skill at the time of the original experience rather than at the time of the test," Hayne said.
She said no one really knew why we had little recollection of experiences prior to ages two or three, and only sketchy memories for some time after that. "The results of this research suggest language acquisition plays a vital role in the development of long-term memory."
The children would be interviewed again at age eight.
"We are particularly interested in whether they will have any memory at all for an event that occurred during their early childhood."
Hayne said childhood amnesia had puzzled psychologists for more than a century.
"Our findings move the field one step closer to understanding why adults experience extreme difficulty when they try to recall experiences from infancy and early childhood."