Welcome to brain Stuff from How Stuff Works. Hey, I'm Christian Sager, and welcome to brain stuff. A lot of things are easy to remember. My high school graduation, for instance, or my first summer job, or that time I got arrested for emptying a bunch of jello packets into Brian Kranston's gas tank. It's it's a long story, but it doesn't take a scientist to notice that adults don't generally remember things that happened before the age of about three
or four. Why is that, well, why can't we remember the earliest events in our lives up to an including birth. Okay, here's an experiment. Try to remember what happened the last time you ate a burrito? Where were you? Who was with you? Was the burrito full of spiders? These kind of memories, being able to recall details of a particular event in the past, are called episodic memories. A person at age sixty will usually have some episode memories from
age thirty. She might not get all the details right, but she will be able to recall some events and explain what happened. But if you take that same person at age thirty and ask her to describe something that happened to her during her first year of life. You'll typically get nothing at all. Sigmund Freud referred to this whole in our memory as childhood amnesia or infantile amnesia.
Freud being Freud explained it by saying we needed to repress memories from infancy because of their inappropriate or traumatic sexual content. But sometimes a blank is just a blank, and contemporary scientists don't tend to throw in with Freud on this one. Another hypothesis that used to be popular says that babies can't form episodic memories until they develop certain cognitive capacities, like language. But there's a major problem
with the language based hypothesis. Experiments have shown that animals like mice also display both long term memory and infantile amnesia. Since childhood amnesia across his species lines, it is probably something to do with brain biology rather than language. One possible answer would be to say that baby brains simply
can't make memories. It's true that memory and coding isn't as efficient in infant brains as it is in the brains of older children or adults, possibly because the prefrontal cortex of a baby's brain hasn't reached maturity yet, but recent studies have shown that very young children can form some memories, leading scientists to think it's not that we don't make memories early in life, but that after a
certain point we can't access them. The memories are made, but something happens to them they get erased or put behind some kind of memory blockade. Patricia Bauer and Marina Larkina of Emory University have led research on this hypothesis. For example, in one study, researchers recorded children at age three describing a recent event, like a trip to a
theme park. Years later, the researchers followed up with these same children to see how much they remembered, and at ages five, six, and seven, the children could recall more than sixty of the earlier events, but by ages eight and nine, their recall was less than More research of this kind is needed, but this looks like watching the onset of childhood amnesia as it happens. Another recent study
has considered the role of neurogenesis in the hippocampus. The hippocampus is a part of the brain that's crucial for creating and storing episodic memories. If you don't have either of your hippocampy, you could end up like that guy in Memento, unable to make new episodic memories. Neuroscientists Shina Jocelyn and Paul Franklin have proposed a theory that childhood amnesia happens because of rapid formation of new cells in the hippocampus when children are young. This is known as
hippocampal neurogenesis. Basically, while your brain is manufacturing lots of the cells you will use to make memories for the rest of your life, it wipes away or obscures the memories you already created as a young child. Check out the brainstuff channel on YouTube, and for more on this and thousands of other topics, visit how stuff works dot com.