because infants don't remember early experiences for long. But exactly why can't we remember wearing ice-cream-cake makeup at birthday party numero uno?
It turns out that the pace of brain development explains this "infantile amnesia" for events in the first year or so of life. (Infancy, obviously, is a time of intense learning: most of us learned to walk, talk, and maybe chew gum --but we did not retain long-term memories of those events).
In recent years, neuroscientists have begun to attribute infantile amnesia to the pace of growth in the frontal cortex, a site crucial for event-memory storage, which develops rapidly at about 12 months.
That notion gets support from a recent experiment by Conor Liston, then a senior, and Jerome Kagan, a professor of psychology at Harvard University. The pair tried to teach babies aged 9, 17 or 24 months to make toys, and found that, four months later, only the older two groups of children remembered how to make the toys.