Speaker 1: Welcome to brain Stuff from How Stuff Works. Hey, brain Stuff,
Speaker 1: I'm Lauren Vogelbam, and I've got another brain Stuff classic
Speaker 1: for you. Our former host, Christian Sagar, explores the puzzling
Speaker 1: question why can't people remember being born? Hey, I'm Christian
Speaker 1: Sagar and welcome to brain Stuff. A lot of things
Speaker 1: are easy to remember. My high school graduation, for instance,
Speaker 1: or my first summer job, or that time I got
Speaker 1: arrested for emptying a bunch of jello packets into Brian
Speaker 1: Kranston's gas tank. It's it's a long story, but it
Speaker 1: doesn't take a scientist to notice that adults don't generally
Speaker 1: remember things that happened before the age of about three
Speaker 1: or four. Why is that, well, why can't we remember
Speaker 1: the earliest events in our lives up to an including birth? Okay,
Speaker 1: here's an experiment. Try to remember what happened the last
Speaker 1: time you ate a burrito? Where were you, who was
Speaker 1: with you? Was the burrito full of spiders? These kind
Speaker 1: of memories, being able to recall details of a particular
Speaker 1: event in the past, are called episodic memories. A person
Speaker 1: at age sixty will usually have some episodic memories from
Speaker 1: age thirty. She might not get all the details right,
Speaker 1: but she will be able to recall some events and
Speaker 1: explain what happened. But if you take that same person
Speaker 1: at age thirty and ask her to describe something that
Speaker 1: happened to her during her first year of life, you'll
Speaker 1: typically get nothing at all. Sigmund Freud referred to this
Speaker 1: whole in our memory as childhood amnesia or infantile amnesia.
Speaker 1: Freud being Freud, explained it by saying we needed to
Speaker 1: repress memories from infancy because of their inappropriate or traumatic
Speaker 1: sexual content. But sometimes a blank is just a blank,
Speaker 1: and contemporary scientists don't tend to throw in with Freud
Speaker 1: on this one. Another hypothesis that used to be popular
Speaker 1: says that babies can't form episodic memories until they develop
Speaker 1: certain cognitive of capacities, like language. But there's a major
Speaker 1: problem with the language based hypothesis. Experiments have shown that
Speaker 1: animals like mice also display both long term memory and
Speaker 1: infantile amnesia. Since childhood amnesia acrosses species lines, it's probably
Speaker 1: something to do with brain biology rather than language. One
Speaker 1: possible answer would be to say that baby brains simply
Speaker 1: can't make memories. It's true that memory encoding isn't as
Speaker 1: efficient in infant brains as it is in the brains
Speaker 1: of older children or adults, possibly because the prefrontal cortex
Speaker 1: of a baby's brain hasn't reached maturity yet. But recent
Speaker 1: studies have shown that very young children can form some memories,
Speaker 1: leading scientists to think it's not that we don't make
Speaker 1: memories early in life, but that after a certain point
Speaker 1: we can't access them. The memories are made, but something
Speaker 1: happens to them, they get erased or put behind some
Speaker 1: kind of memory blockade. Patricia Bauer and Marina Larkina of
Speaker 1: Emory University have led research on this hypothesis. For example,
Speaker 1: in one study, researchers recorded children at age three describing
Speaker 1: a recent event, like a trip to a theme park.
Speaker 1: Years later, the researchers followed up with these same children
Speaker 1: to see how much they remembered, and at ages five, six,
Speaker 1: and seven, the children could recall more than sixty percent
Speaker 1: of the earlier events, but by ages eight and nine,
Speaker 1: their recall was less than More research of this kind
Speaker 1: is needed, but this looks like watching the onset of
Speaker 1: childhood amnesia as it happens. Another recent study has considered
Speaker 1: the role of neurogenesis in the hippocampus. The hippocampus is
Speaker 1: a part of the brain that's crucial for creating and
Speaker 1: storing episodic memories. If you don't have either of your
Speaker 1: hippocamp i, you could end up like that guy in Memento,
Speaker 1: unable to make new episodic memories. Neuroscientists Sina Jocelyn and
Speaker 1: Paul Franklin have proposed a theory that childhood and nisia
Speaker 1: happens because of rapid formation of new cells in the
Speaker 1: hippo campus when children are young. This is known as
Speaker 1: hippocampal neurogenesis. Basically, while your brain is manufacturing lots of
Speaker 1: the cells you will use to make memories for the
Speaker 1: rest of your life, it wipes away or obscures the
Speaker 1: memories you already created as a young child. Today's episode
Speaker 1: was written by Joey McCormick and produced by Tyler Clang.
Speaker 1: If you miss Christian, check out his current pop culture podcast,
Speaker 1: super Context, and check out our online story at public
Speaker 1: dot com slash brain Stuff. Every purchase supports brain Stuff directly,
Speaker 1: and of course for more on this and lots of
Speaker 1: other memorable topics, visit our home planet, how stuff works
Speaker 1: dot com