The phenomenon, known as "childhood amnesia
," has been puzzling psychologists for more than a century -- and we still don't fully understand it.
At first glance, it may seem that the reason we don't remember being babies is because infants and toddlers don't have a fully developed memory. But babies as young as six months can form both short-term memories that last for minutes and long-term memories that last weeks, if not months.
In one study, six-month-olds who learned how to press a lever to operate a toy train remembered how to perform this action
for two to three weeks after they had last seen the toy. Preschoolers, on the other hand, can remember events that go years back. It's debatable whether long-term memories at this early age are truly autobiographical, though -- that is, personally relevant events that occurred in a specific time and place.
Of course, memory capabilities at these ages are not adult-like -- they continue to mature until adolescence. In fact, developmental changes in basic memory processes have been put forward as an explanation for childhood amnesia, and it's one of the best theories we've got so far. These basic processes involve several brain regions and include forming, maintaining and then later retrieving the memory.
, thought to be responsible for forming memories, continues developing until at least the age of seven. We know that the typical boundary for the offset of childhood amnesia -- three and a half years -- shifts with age
. Children and teenagers have earlier memories than adults do. This suggests that the problem may be less with forming memories than with maintaining them.
But this does not seem to be the whole story. Another factor that we know plays a role is language. From the ages of one to six, children progress from the one-word stage of speaking to becoming fluent in their native language(s), so there are major changes in their verbal ability that overlap with the childhood amnesia period. This includes using the past tense, memory-related words such as "remember" and "forget" and personal pronouns, a favorite being "mine."
It is true to some extent that a child's ability to verbalize about an event at the time that it happened predicts how well they remember it months or years later. One lab group conducted this work
by interviewing toddlers brought to accident and emergency departments for common childhood injuries. Toddlers over 26 months, who could verbalize about the event at the time, recalled it up to five years later, whereas those under 26 months, who could not talk about it, recalled little or nothing. This suggests that preverbal memories are lost if they are not translated into language.
Social and cultural effects
However, most research on the role of language focuses on a particular form of expression called narrative
, and its social function. When parents reminisce with very young children about past events, they implicitly teach them narrative skills -- what kinds of events are important to remember and how to structure talking about them in a way that others can understand.
Unlike simply recounting information for factual purposes, reminiscing revolves around the social function of sharing experiences with others. In this way, family stories maintain the memory's accessibility over time, and also increase the coherence of the narrative, including the chronology of events, their theme, and their degree of emotion. More coherent stories are remembered better. Maori adults have the earliest childhood memories
(age 2.5) of any society studied so far, thanks to Maori parents' highly elaborative style of telling family stories.
Reminiscing has different social functions in different cultures, which contribute to cultural variations in the quantity, quality and timing of early autobiographical memories. Adults in cultures that value a