Most of us don’t have any memories from the first three to four years of our lives – in fact, we tend to remember very little of life before the age of seven. And when we do try to think back to our earliest memories, it is often unclear whether they are the real thing or just recollections based on photos or stories told to us by others.
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. For example, the hippocampus, 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 favourite being “mine”.