While a baby's experiences and memories are vital to his/her development, most of us can't remember what we did before our third birthday. Why is that?

It may be that as babies we just don't have the necessary mental equipment to store and organize memories properly, a hypothesis strengthened by the famous case of Henry Molaison. Molaison was unable to remember any new events that happened to him after a faulty brain operation. Though he still had temporary short-term memory and could learn new skills, he couldn't retain information for long.

We know that neurons continue to be added to our brains in our early years, and it's possible that when this building process has finished, memories can start to form.

Another hypothesis is that our sense ...