A recent study shows that to persist, memories need to be encoded into language. The result: kids aren't able to remember things that predate their ability to put it into language.
[update: at 11:43PM one night, two months after his daughter is born, Matt Haughey puts it in terms of our brain's programming language:
"Imagine we have no media and everything's in RAM, as it happens.
10 PRINT "CRY LOUDLY"
20 GOTO 10
A few months into life and we move on to encoding everything in MS-DOS..."]