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Speaker 1: Welcome to brain Stuff from How Stuff Works. Hey, brain Stuff,

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Speaker 1: I'm Lauren Vogelbam, and I've got another brain Stuff classic

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Speaker 1: for you. Our former host, Christian Sagar, explores the puzzling

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Speaker 1: question why can't people remember being born? Hey, I'm Christian

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Speaker 1: Sagar and welcome to brain Stuff. A lot of things

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Speaker 1: are easy to remember. My high school graduation, for instance,

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Speaker 1: or my first summer job, or that time I got

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Speaker 1: arrested for emptying a bunch of jello packets into Brian

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Speaker 1: Kranston's gas tank. It's it's a long story, but it

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Speaker 1: doesn't take a scientist to notice that adults don't generally

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Speaker 1: remember things that happened before the age of about three

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Speaker 1: or four. Why is that, well, why can't we remember

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Speaker 1: the earliest events in our lives up to an including birth? Okay,

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Speaker 1: here's an experiment. Try to remember what happened the last

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Speaker 1: time you ate a burrito? Where were you, who was

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Speaker 1: with you? Was the burrito full of spiders? These kind

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Speaker 1: of memories, being able to recall details of a particular

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Speaker 1: event in the past, are called episodic memories. A person

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Speaker 1: at age sixty will usually have some episodic memories from

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Speaker 1: age thirty. She might not get all the details right,

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Speaker 1: but she will be able to recall some events and

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Speaker 1: explain what happened. But if you take that same person

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Speaker 1: at age thirty and ask her to describe something that

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Speaker 1: happened to her during her first year of life, you'll

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Speaker 1: typically get nothing at all. Sigmund Freud referred to this

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Speaker 1: whole in our memory as childhood amnesia or infantile amnesia.

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Speaker 1: Freud being Freud, explained it by saying we needed to

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Speaker 1: repress memories from infancy because of their inappropriate or traumatic

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Speaker 1: sexual content. But sometimes a blank is just a blank,

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Speaker 1: and contemporary scientists don't tend to throw in with Freud

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Speaker 1: on this one. Another hypothesis that used to be popular

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Speaker 1: says that babies can't form episodic memories until they develop

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Speaker 1: certain cognitive of capacities, like language. But there's a major

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Speaker 1: problem with the language based hypothesis. Experiments have shown that

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Speaker 1: animals like mice also display both long term memory and

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Speaker 1: infantile amnesia. Since childhood amnesia acrosses species lines, it's probably

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Speaker 1: something to do with brain biology rather than language. One

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Speaker 1: possible answer would be to say that baby brains simply

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Speaker 1: can't make memories. It's true that memory encoding isn't as

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Speaker 1: efficient in infant brains as it is in the brains

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Speaker 1: of older children or adults, possibly because the prefrontal cortex

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Speaker 1: of a baby's brain hasn't reached maturity yet. But recent

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Speaker 1: studies have shown that very young children can form some memories,

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Speaker 1: leading scientists to think it's not that we don't make

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Speaker 1: memories early in life, but that after a certain point

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Speaker 1: we can't access them. The memories are made, but something

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Speaker 1: happens to them, they get erased or put behind some

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Speaker 1: kind of memory blockade. Patricia Bauer and Marina Larkina of

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Speaker 1: Emory University have led research on this hypothesis. For example,

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Speaker 1: in one study, researchers recorded children at age three describing

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Speaker 1: a recent event, like a trip to a theme park.

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Speaker 1: Years later, the researchers followed up with these same children

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Speaker 1: to see how much they remembered, and at ages five, six,

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Speaker 1: and seven, the children could recall more than sixty percent

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Speaker 1: of the earlier events, but by ages eight and nine,

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Speaker 1: their recall was less than More research of this kind

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Speaker 1: is needed, but this looks like watching the onset of

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Speaker 1: childhood amnesia as it happens. Another recent study has considered

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Speaker 1: the role of neurogenesis in the hippocampus. The hippocampus is

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Speaker 1: a part of the brain that's crucial for creating and

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Speaker 1: storing episodic memories. If you don't have either of your

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Speaker 1: hippocamp i, you could end up like that guy in Memento,

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Speaker 1: unable to make new episodic memories. Neuroscientists Sina Jocelyn and

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Speaker 1: Paul Franklin have proposed a theory that childhood and nisia

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Speaker 1: happens because of rapid formation of new cells in the

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Speaker 1: hippo campus when children are young. This is known as

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Speaker 1: hippocampal neurogenesis. Basically, while your brain is manufacturing lots of

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Speaker 1: the cells you will use to make memories for the

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Speaker 1: rest of your life, it wipes away or obscures the

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Speaker 1: memories you already created as a young child. Today's episode

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Speaker 1: was written by Joey McCormick and produced by Tyler Clang.

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Speaker 1: If you miss Christian, check out his current pop culture podcast,

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Speaker 1: super Context, and check out our online story at public

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Speaker 1: dot com slash brain Stuff. Every purchase supports brain Stuff directly,

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Speaker 1: and of course for more on this and lots of

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Speaker 1: other memorable topics, visit our home planet, how stuff works

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Speaker 1: dot com