system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why we don't start making long term memories until around the age of 5.

Most people's earliest memories seem to be from the age of 4-5, why is this?
gpt
Most recently researchers have attributed it to a child's lack of self-perception, language, or other mental equipment required to keep memories.

More in depth: rapid neuron growth during early childhood disrupts the brain circuitry that stores old memories, making them inaccessible. Young children also have an underdeveloped prefrontal cortex, another region of the brain that encodes memories, so infantile amnesia may be a combination of these two factors.

EDIT: Because someone requested a literal five year old explanation: you haven't learned how to remember things yet.