I'll have to look for the reference later, but my recollection of the research is that it is more common for PG kids to have extremely early memories (some back into infancy, or even, rarely, of the birth experience) than it is for NTs, but by no means uniformly so. Some individuals at every cognitive level have very good autobiographical memory, while others do not. Similarly for acquired knowledge and skills. Rate of learning is one thing, while long-term retention is another.
A general factor regarding autobiographical memory is that most NT children go through a process of memory coalescence between about age 7 and 10 (probably corresponding to a stage of brain development that involves a fair amount of pruning of neuronal connections), during which a reasonably stable, cohesive narrative of early childhood appears to be formed. Up until that point, free recall of early memories seems to be fairly even-handed. After that time, most people pare down their memories of early childhood to a set of stories that are told and re-told.
