Till date, scientists knew that few adults can remember events in their lives that happened prior to age three.
Psychologists at Emory University in Georgia, US, have now documented the onset of childhood amnesia.
"Our study is the first empirical demonstration of the onset of childhood amnesia. We recorded the memories of children, and then we followed them into the future to track when they forgot these memories," said psychologist Patricia Bauer at Emory University.
The research involved interviewing children about past events in their lives, starting at age three.
The researchers focused on how episodic, or autobiographical memory, changes through childhood and early adulthood.
Different subsets of the group of children were then tested for recall of these events at ages five, six, seven, eight and nine, said the study published in the journal Memory.
"Knowing how autobiographical memory develops is critically important to understanding ourselves as psychic beings. Remembering yourself in the past is how you know who you are today," said Bauer.
The experiment began by recording 83 children at age three, while their mothers or fathers asked them about six events that the children had experienced in recent months, such as a trip to the zoo or a birthday party.
After recording these base memories, the researchers followed up with the children years later, asking them to recall the events that they recounted at age three.
One surprising finding was that although the five-and-six year-old children remembered a higher percentage of the events, their narratives of these events were less complete.
The older children remembered fewer events, but the ones they remembered had more detail, said Bauer.
"Young children tend to forget events more rapidly than adults do because they lack the strong neural processes required to bring together all the pieces of information that go into a complex autobiographical memory," she explained.
Sigmund Freud, an Austrian known as the founding father of psychoanalysis, had coined the term 'childhood amnesia' to describe this loss of memory from the infant years.