What Happened When I Was Four?

Katy Waldman looks at the distribution of our memories:

Autobiographical memories are not distributed equally across the lifespan. Instead, people tend to experience a period of childhood amnesia between birth and age 5, a reminiscence bump between age 10 and age 30 (with a particular concentration of memories in the early 20s), and at any age, a vivid period of recency from the present waning back to the end of the reminiscence bump.

At first, researchers proposed that the reminiscence bump coincided with a phase of developing mental firepower. Young adults encoded more information about the world because they were using state-of-the-art biological equipment, the theory went—relatively fresh and agile minds. As cognitive function declined with age, the flood of recorded memories would naturally slow to a trickle, though recent experiences would remain accessible.

Going deeper into the mechanisms of recall, scientists also noted that the brain transcribes novel experiences more readily than mundane ones. For instance, a 1988 study found that 93 percent of vivid life memories concern unique or first-time events. Might the reminiscence bump reflect the fact that late adolescence and early adulthood are suffused with “firsts” (first relationship, first time leaving home, first job, first marriage, first child)?

I guess that's why I remember almost every line from Billy Madison, but only two or three things before I am 5.  I've told parents before that it is great that their kids won't remember almost anything from their first five years, but the parents are usually still worried they'll scar their kids for life.  I don't think they will.