Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
Speaker 1 (00:02):
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
(00:25):
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
(00:46):
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
(01:09):
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
(01:30):
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
(01:54):
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
(02:14):
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
(02:35):
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
(02:58):
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
(03:18):
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
(03:42):
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
(04:04):
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.