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PROFESSOR: So let's talk about
memory today and the fragile
power of memory.
If memory didn't work, we
wouldn't remember anything.
We wouldn't learn anything.
So we know it has to
work reasonably.
But it has a number of fragile
aspects we'll talk about
where, of course, we
forget things.
But on top of that, it turns out
there's ways in which our
memories get less accurate and
distorted, are not actual
records of our experience but
rather interpretations or our
memory of our memory.
And we'll talk about experiments
that reveal that.
So to a large extent, we'll
talk about what do we know
from scientific research about
why we remember some of our
lives and why we forget so
many other things that we
experience.
And a version of the way people
sometimes think about
it is in what sense is memory
like a camera, that every
experience you have is stored
in your mind somewhere?
We all have the experience,
perhaps, that something will
remind you of something you
haven't thought about for
days, weeks, or years.
And you go, oh, well they must
be all stored there.
I just need the right
cue or the right
path to get that memory.
So that's one version
of memory,
everything is in us recorded.
Sometimes we can get to it.
Sometimes we can't.
Another version is the way to
think about your memory.
It's kind of like
a punch bowl.
You put in some milk.
And then you put in
some orange juice
and swirl it around.
And then you put in some
Coca-Cola and swirl it around.
And it's not a desirable drink
that you have in your bowl.
But you can no more get the
specific milk, or the specific
orange juice, or the
specific Coke.
Because they're all
mixed together.
And is memory more like that?
As life goes on, things
get mixed in.
And the raw memory is never
recoverable from the mixture
of subsequent experiences,
thoughts, and feelings.
So we'll bring the same
perspective a little bit.
Bottom-up memory might be really
the video camera if we
had it, an actual recording of
what we hear, what we see,
what we experience out
there in the world.
Top-down processes are the
mental things we have in our
minds that let us interpret
what's out there, concepts,
expectations.
Also, it turns out, you'll see
that subsequent experiences go
back and change memories
from prior times.
And which of these things, the
bottom-up original experience,
or the top-down interpretation
grows over time to constitute
your memory?
So we can have a very simple
model of memory,
a flash for a moment.
I'll give you an example of
how people test this, a
sensory memory, very
tiny moments only.
Short-term memory that you can
rehearse in some cases.
Somebody tells you a number, And
you can repeat it over and
over again.
You have that capacity.
And then long-term memory,
things that
last for a long time.
You can define these things
many different ways.
When we talk about the brain
organization of human memory,
we'll say that short-term
memory is
probably, lasts seconds.
And everything after that
is long-term memory.
Now, of course, if you just
experienced something, you'd
remember it better.
If it's a week, a month, a year,
five years from now,
most likely less better.
So time passes.
But we think almost all of
that is in the context of
long-term memory capacities
of your mind.
So here's a kind
of experiment.
We'll do a couple of exercises
at your seat.
But this I'm just going
to give you a feeling.
Because this would require
millisecond
timing to do correctly.
But the way they approached this
sensory memory, the flash
of memory, just capturing for a
moment what's out there, is
something like this.
So imagine your job is
to report back the
letters that you see.
OK.
Yeah, you're getting
a number of them.
So you just did what's called
a whole report method.
Tell me everything you saw.
They did another approach,
which is present letters.
And then just as it disappeared
did we get a tone,
a high, medium, or low tone.
And that would tell them which
row to report, the top row,
the middle row, or the bottom
row depending on the tone they
heard just after the flash,
immediately after the flash.
Does make sense?
OK.
It's gone.
But the tone is telling you
which one to report.
And the striking finding
in this was this.
If they showed you 12 letters
like you just saw, and said,
tell me everything you see,
people could give you about
four letters back.
Maybe you had that experience,
about four letters accurately.
If they gave you the letters,
they flashed them, then you've
got the tone.
For one row only, you've got
about three letters correct.
Now this is interesting.
The letters are gone.
But it's kind of like as
if the photograph of
your memory is fading.
But if you put your attention
somewhere, you can still pull
it back, but just a
little bit of it.
Because here you get
four out of 12.
Here you get three out of 12.
Almost the same because your
attention can zoom in on that
fading mental image of
what you just saw.
So much is sensed.
But attention only selects a
little bit to be remembered.
So that's this very first
moment of memory.
One of the more impressive lines
of research is the next
moment, short-term memory,
keeping in mind something in
your mind briefly.
And one of the most striking
aspects of human short-term
memory is limited in how
much it can hold.
And across a tremendous range of
materials, words, letters,
shapes, tones, and so on, you
can hold approximately 7 plus
or minus 2 chunks of
information, limited
short-term memory.
So now I need somebody who's
willing, at their
chair, to do something.
I'm going to read to you
numbers, and ask you
to repeat them back.
But your eyes will need
to be closed.
And it'll be fairly
challenging.
All right, thank
you very much.
OK.
Close your eyes.
And here we go.
Ready?
Keep your eyes closed
until we're done.
Repeat after me.
6, 1.
AUDIENCE: We're repeating
as you say it or after?
PROFESSOR: When I'm done.
I'm sorry, yeah.
Ready?
6, 1, 9.
4.
Repeat.
AUDIENCE: 6, 1, 9, 4.
PROFESSOR: Right.
Ready?
3, 7, 8, 5, 2, repeat.
AUDIENCE: 3, 7, 8, 5, 2.
PROFESSOR: Great.
Ready?
9, 6, 5, 2, 8, 3, repeat.
AUDIENCE: 9, 6, 5, 2, 8, 3.
PROFESSOR: Great.
Ready?
4, 2, 6, 9, 8, 5, 1.
repeat.
AUDIENCE: 4, 2, 6, 9, 8, 5, 1.
PROFESSOR: Very good.
Ready?
8, 1, 6, 3, 7, 2, 4, 9.
Repeat.
AUDIENCE: 8, 1, 6,
7, 4, 2, 1, 9.
PROFESSOR: OK, perfect.
OK your eyes.
Thank you very much.
You did terrific.
You got four right, five right,
six right, seven right,
eight right, you got
them mostly right.
You just reversed one or two.
Seven plus or minus two, it
doesn't matter how smart you
are, how advanced you are.
There used to be some confusions
about this.
Because they would say kids in
different countries have
different limits.
And they'd say our country is
smarter than your country, or
our educational system
is better than
your educational system.
It turned out that all of that
got equated around the world
if you counted up the
number of syllables
that are in the digits.
The real unit of memory
here are syllables.
So in English, most of the
numbers are one syllable.
1, 2, 3, 4, 5, 6 are
all one syllable.
7 gets two.
8 is one syllable.
9 is one syllable.
In some other languages, the
words that go with the digits
are two syllables.
So countries that have two
syllables, they have lower
spans not because they were
dumber or had a worse
education system.
It's because the real unit
is number of syllables.
Because you're hearing it.
It's language.
So around the world, it's the
fundamental capacity of the
human mind is that
you're limited to
these kinds of stuff.
So how do we get around that?
Why are we not always barely
able to do anything with very
small amounts of information?
So it's just a constraint
of our minds.
It's because background prior
knowledge, things you know
before you have to learn
something, has a
very powerful effect.
It allows you for the
information to
be retained in memory.
But it has a double-edged sword,
which is kind of a
theme a lot today.
As much as it helps you remember
things, it can fool
you into misremembering
things.
And let me give you a
concrete example.
So you can put chess displays
in front of people who are
either beginning chess players,
have played for a
while, or are masters.
And they're not going to play.
They're going to look at it.
The pieces will be swept
to the side.
And then they have to put all
the pieces back out of memory
into the same location where
they just saw it.
They know that's going
to happen.
So it's a memory test.
Here's the pieces.
Take a look.
The examiner sweeps the
pieces to the site.
And you put them back
as well as you can.
You see it.
It gets swept to the side.
And you reproduce it from memory
what you just saw.
And here's the performance of
master players and beginner
players in this case, so people
who have played a lot
of chess and people who have
played very little chess.
It's better to be high, the
number of correct pieces.
And there's two kinds
of displays.
In one kind of displays
is what we
call the normal displays.
Those are ones that
could really have
happened in the game.
They were kind of reasonable
configurations of pieces.
The random displays are pieces
all over the place in a
configuration that you're not
likely to see in a real game
of chess, equal number
of pieces.
And look what happens.
The best performance are master
players who see a real
normal chess configuration.
Here are the players
who are beginners.
And look at the worst
performances, the chess
masters who see a
random set up.
So what do you guess
is happening?
Yeah?
AUDIENCE: People who
play chess a lot
memorize games and positions.
So they're used to seeing
those patterns.
And when they see a random
configuration, they can't
recreate it as well.
PROFESSOR: Right.
So the people who have played
chess a lot have a lot of
configurations in their mind,
background knowledge.
They use that background
knowledge of what a chess
array means.
Somebody's in trouble,
somebody's winning, something
interesting is happening
in this corner.
That knowledge helps them escape
the boundaries of seven
plus or minus two.
And they do a lot better than
the beginners for whom it
doesn't mean much.
It's just a bunch of stuff out
there hard to remember.
But what happens here when
the pieces are random?
The chess masters are making
mistakes because they're
putting the pieces in the places
they ought to be rather
than the places they perversely
were randomly located.
If you're a chess player, you
don't like that random board.
It doesn't feel right.
But they're trying
to be accurate.
But now they're misplacing their
memory for what they
actually saw with their
mental model of what
ought to be out there.
Now the players who are not so
good, you don't see much of a
difference between
these lines.
They don't understand
when it's random.
They don't understand
when it's organized.
It's just a bunch of pieces.
So the double-edge of background
knowledge.
Background knowledge lets you
escape the bounds of limited
short-term memory but at a cost
of sometimes substituting
in for the actual experience
you have.
So we'll try this.
And people use the word
"chunking" as the way in which
you use your background
knowledge to get big pieces of
information stored that are
better than you think for
short-term memory limits.
So here's a quick one.
I need a volunteer actually.
It's not too bad.
Wow, tough volunteer day.
You're mad at me
about the exam.
OK.
Thank you.
OK, ready?
What were the letters?
AUDIENCE: [INAUDIBLE].
PROFESSOR: OK.
How about these ones?
[LAUGHTER]
PROFESSOR: The same letters,
it's just that
now you see the chunks.
And you can map them onto
long-term memory more easily.
Plus I showed them longer.
Anybody else want to try
something like this?
Thank you.
Here we go.
What letters do you see?
Ready?
AUDIENCE: [INAUDIBLE].
PROFESSOR: OK.
Now I'm going to let your
background knowledge triumph.
Ready?
It's the same letters.
Same letters, all it is, is your
background knowledge is
useless, your knowledge of
words, your knowledge of the
alphabet, useless.
It's the same information in a
sense, same number of letters,
same identity of letters.
But now your background
knowledge is powerful.
I need somebody else,
one more volunteer.
Thank you.
I'm going to show
you a sentence.
This is meant to be hard,
the first one.
Don't worry about it.
OK?
Here we go.
Can you tell me what
they were?
AUDIENCE: Leaf, paper,
steer, car, beach.
PROFESSOR: That's pretty good.
Let me show you another
equal number of words.
Ready?
Go OK, what is it?
AUDIENCE: While I was walking
around-- while I was walking--
PROFESSOR: You would
do better.
OK It's hard to pull
these things off.
So 13 words, people would
do pretty miserably.
Although you did very well,
a lot better at this.
Because, again, you can use your
background knowledge of
what does a sentence mean?
What's the ergative syntax?
All your background knowledge
can be applied.
Again, the power of background
knowledge is immense.
I can tell you that if you go
work somewhere, or if you're
working in a lab now, or if
you're working in any place,
you might be impressed by people
who are older than you,
and what they know, and what
they can learn and pick up.
It's background knowledge,
background knowledge,
background knowledge.
It lets you quickly understand
an idea, because you can
interpret it from prior ideas
that you know, quickly read a
paper, because you can slot it
into prior things you know.
Background knowledge is
incredibly powerful to let you
discover the signal and get
a lot of the specific
information in any kind of
information out there.
Tyler, I left with
you this time.
Sorry.
So we're going to do a
quick memory test.
You will do it at
your own seat.
It's voluntary.
But I will ask you to share a
little bit of information.
This is for everybody now,
not for one person to
be put on the spot.
So what I'm going to do is read
you a list of words, wait
until the end.
And when I say, recall,
write down the
words from your memory.
So I'll wait for a moment
for you to get a
pencil or pen or something.
OK.
I see a few people still
getting stuff.
OK, ready?
Here comes the word.
Just listen, don't write.
That would be too easy.
I'll say recall, and then
write them down.
Here we go.
Mailbox, sardine, shotgun,
peacock, credit, detail,
flicker, airline, spinach,
clarinet.
Recall.
OK.
Here are the answers.
As you look at this list, put
your hand up if you've got all
10, 9, 8, 7, 6, 5, 4, 3, 2.
Thank you.
All right.
So think about this
for a moment.
We said seven plus
or minus two.
When the words are presented in
a random, unorganized list
like this, you're pretty much
back to short-term memory
limits in many senses, not
completely, but in many ways.
So if you were to tell a person
on the street, I mean,
I have to say two things about
you guys, which is certainly
true and complimentary.
Most of you, if you're somewhere
between 18 and 25,
you're at your peak memory
capacity for the
rest of your life.
You will never do better
for rote learning then
you are right now.
There's a ton of research
that shows that.
You will never do better
for rote learning
than about 18 to 25.
After that it's downhill.
You get other benefits.
Salaries go up a little bit.
You get authority.
That's a nice one.
But rote memory, you're
at the top.
Not only are you at the top,
but you are an incredibly
selected academically
achieving group.
You're MIT undergraduates.
You're incredibly selected to be
the top of the top, in many
senses, for learning between 18
to 25 as far as MIT could
possibly figure this out.
You are our hope
for the future.
If you guys can't fix global
warming, we're in trouble.
So you can't get 10 words?
Come on.
We have big problems to solve.
It's a capacity of the human
mind that we just can't do
about more than this.
It's just amazing how limited
rote memory is
without other things.
But there's a little bit
more than we can tell.
How many of you got mailbox
and sardine?
A fair number of hands.
OK.
How many of you got spinach
and clarinet,
the last two words?
How many of you got
credit and detail?
Way fewer hands.
And that's what happens under a
well-controlled experiment.
So this is correct.
High is correct.
This is what order the word
was in the first word you
heard, say the fifth.
This experiment is 15 words.
You can see that.
Here's their performance.
Two things are noteworthy.
People do best for the first
couple of words.
And sometimes they did best for
the last couple of words.
So here's three delays.
These delays are zero
seconds what we did.
You get the list, you
immediately write them down
and recall them verbally.
That's zero, immediate.
Or I wait 10 seconds and
then say, now recall.
Or I wait 1/2 minute and
say, now recall.
Now memory for the first two
items is what's called a
primacy effect.
It doesn't matter.
In all three conditions, those
are the best two remembered
words, on average, for most
of the experiment.
And people think that's a
signature of long-term memory.
You can get those one
or two words.
And then you start to
get overwhelmed
in long-term memory.
Here, you only get the boost for
the last couple of words
if there's zero second delay.
If there's 10 seconds or 30
seconds delay, no boost.
So people interpret this recency
effect, superior
memory for the last couple of
words, as a signature of
short-term memory that
lasts only seconds.
And so in that simple
experiment, you can see
long-term memory influences,
short-term memory influences.
And short-term is
very short-term.
It's just seconds.
Now Ebbinghaus is one of the
founders of experimental
studies of memory.
And he was heroic.
He would just train himself.
He would use nonsense syllables,
because he wanted
to get rid of a lot of
background stuff, rote memory.
And he would learn thousands of
these and then test himself
and score himself honestly.
He did the bulk of the
work on himself.
And he discovered something
that's pretty simple, but that
has had a huge effect.
So how well do you do since you
learned something all in
long-term memory if you're
tested immediately?
100% if it's small list
and you studied a lot.
20 minutes later, an hour later,
nine hours later, you
can see the steep forgetting
up until about 10 hours.
And then it sort of
hangs in there.
The forgetting curve of
long-term memory, immediately
afterwards, we're pretty good.
Then there's a lot of forgetting
in 20 minutes, and
for a day, and then things
hang in there.
This is a shaped asymptotic
curve of forgetting.
OK now here's another
mission for you.
You need a pencil.
Or just your fingers will
work fine either way.
You're going to see
a list of words.
Some will be in uppercase.
Some will be in lowercase.
Capital letters, uppercase.
All right.
Your job as you see them from
top to bottom is to tap your
left hand for each word that's
in the capital letter and your
right hand for each word that's
a lowercase letter.
Is that OK?
So if the first work is capital,
you tap left. if the
second word is lowercase,
you tap right.
So you just tap, tap, tap until
you get to the bottom.
And then it will go.
You already?
You ready to help me out?
Here we go.
Thank you very much.
Here we go.
Excellent.
All right.
What were words?
[LAUGHTER]
PROFESSOR: You might be
impressed that even though
they were right in front of you,
and even though you were
looking whether they were upper
and lowercase case so
you really saw them, if you
don't bring the relevant
background knowledge to
remembering it, which is the
meaning of words most
the time, our
memory is pretty hideous.
All right.
try another one.
Now the trick is gone
a little bit.
This is a little bit
of a set up.
But I can tell you it's
scientifically true.
So now it's the same idea.
You can see words.
You can read the word, if it's a
living thing like a dog, tap
the left hand.
If it's a nonliving thing like
a chair, the right hand.
Ready?
You did awesome.
Thanks.
Here we go.
OK.
Does it feel like you would
remember the words better?
Does it feel like you would?
OK.
So here's what we did.
The first list, is you
thought about the
appearance of the word.
In memory, that's called shallow
encoding, just if it's
upper and lowercase.
And typically, that leads
to pretty poor memory.
If you think about the meaning
of the word, we think that
optimizes memory.
People would call it
deep encoding.
And it leads to better memory.
And in a well-controlled
experiment, now here we had a
certain order.
And you knew there
was a trick.
But if you had a well-controlled
experiment,
here's what you'd find.
If you just think about the
appearance of the word, here's
how well you do, pretty
low if you see the
word once or twice.
And if we look over here at the
meaning of the word you,
can see one thought about the
meaning of the word is better
than two presentations thinking
about the appearance.
And two thoughts about the
meaning of the word, and your
memory's really excellent.
Yeah, question?
AUDIENCE: So if you're forced
to think about--
get confused by the uppercase
and the lowercase and the
living versus the non-living--
PROFESSOR: Were they confusing
to do one then the other?
It was a little bit, right?
AUDIENCE: Is that supposed to
make you remember it better?
You have to think that
hard about it?
PROFESSOR: No.
The question is, is the
confusion of doing two
different tests help you out?
So, roughly speaking, the answer
is to the extent it
draws your attention more
to the word, yes.
To the extent you're
sitting there
going, OK, was it uppercase?
Or was it living?
This is weirding me out.
It's going to hurt you, because
your mind is filled
with those thoughts
not looking at
what's in front of you.
In these demonstrations, they're
a little cloogy.
Here's a fun one, the
effective context.
So this is how they did
the experiment.
You can do it different ways.
But this is a fun one.
They actually went
in the United
Kingdom to the shoreline.
And they had people put on
these old style diving
helmets, the old big helmets.
And you go under the water with
the big hose in front of
you to your air source.
And they had them learn word
lists, like you were looking
at word lists, on the
land or underwater.
And then they were tested
for this on the
land or in the water.
And the core message was, you
do better remembering
information if you're tested in
the same situation in which
you learned it.
So what we see here is here's
the words learned underwater.
You're better if you're tested
underwater instead of
going on the land.
If you learned the word on the
land, you're better off if you
test on the land than if
you go underwater.
The context in which you learned
something helps you.
Studying underwater and tested
under water, you do better
than studying underwater and
going on land or vice versa.
Being in the same room, same
time of day, all those things
help you a little bit to
bring a memory back.
Because those are parts of the
memory in the context in which
you experience it.
Another approach that people
have taken, this is about
organization.
They'll present a set of words
like this and ask people to
try and remember them.
It's a pretty big list.
But if you take the same words
and do that, same words people
remember a lot better,
because there's an
organization that helps you.
Your background knowledge of
what is a career, what is
housework, what is a food all
contribute to helping your
memory for these items
be better.
So let's think about
forgetting.
We know something
from last year.
We forgot it.
There's a least two ideas that
people have said, what's the
core reason we forget things?
One of them is like passive.
Well, I haven't used
it in a while.
It's just not available
anymore.
Because time has passed.
It's not been used.
It's not available.
That's passive forgetting.
The other way to think about why
we forget is not that it's
a passive loss of knowledge.
But that experiences you have
after that moment when you
learned something, will go
back and write over, and
muddy, and confuse your memory
for the original event.
It's active interference of
subsequent experience.
It's not passive withering.
Other stuff is getting in your
head that's writing over and
modifying the original memory.
And the original memory
is never there again.
And people have talked about it
in two different directions
that you can think about this.
One of them is what you call
proactive interference where
things from before mess up your
learning on something.
Or retroactive interference, you
already have the memory.
And now new things mess you up
and write over the memory.
So memory is threatened by
what came before they
experience or what happens after
the experience In the
way that it interferes with
accuracy of memory.
So here's a fun experiment.
It's just two subjects.
But there's a lot of other
studies that looked at this.
This is the original
demonstration where people had
to remember syllables.
And they taught them the
syllables just before they
went to sleep or as
they woke up.
And in each case, they were
tested, for example, some
number of hours later.
Let's say eight hours later.
And their idea in the study--
and there's one wrinkle I'll
mention now that we
know things--
their idea was when you go to
sleep, there's no retroactive
interference.
Because you're not learning
anything else.
You're not experiencing.
You're not talking.
You're not reading.
So when you wake up in the
morning, nothing has messed up
your memory from when you
just went to sleep.
Does that make sense?
If you study in the morning,
now you go and
you have your day.
You go to classes you
talk to people.
You read things.
All those new experiences can go
back and mess up the memory
you acquired to start with.
So in both cases, you get the
memory to start with.
But in one case, you're sleeping
for eight hours.
It's not messed up.
In the other case, you were
out in the world.
Lots of new things are
happening that are
retroactively messing
up the memory.
And you can see the people who
slept after who slept after
they learned, when they woke up,
did a lot better than the
people who walked around
during the day.
And that thought can be one of a
huge line of research saying
that one of the reasons that
memories become available to
us is not simply passive
withering, but active other
mental experiences that block
right over and change the
original memory.
Question, yeah.
AUDIENCE: Studying at night, and
they going to sleep, does
just having those memories
hanging around in your brain
strengthen them?
Because you're going to
wake up and do stuff--
PROFESSOR: Yeah.
So now there's a second thing.
The question is, is there
something good about going to
sleep after studying?
And the answer is, there's
a lot of evidence now in
animals, and increasingly in
humans, that sleep is a period
that fixes memories from
the prior day.
And if you don't get the right
kind of sleep or something
like that, those memories from
the prior day don't seem to
get as well fixed into
long-term memory.
So this is mixing those
two issues.
These people have two advantages
now we think.
One advantage they have is
they're not having new
experiences during the night
that are messing up
the memory they got.
And they're having this
consolidation
period during sleep.
People have long studied
what's the use of sleep
besides making you not sleepy?
And one of the most fascinating
things-- and
there's just more and more
evidence for this--
it's a period where because our
brain is kind of quiet in
many ways, it seems to work a
lot on fixing memories from
that day into a better
long-term unit.
So those people have two
advantages by our current
understanding.
So that's retroactive
interference.
Let me give you an example of
proactive interference.
And here's how they study it.
We won't to try it.
But let me give you
an example.
They would have you hear
three words like
banana, peach, and apple.
They're all related.
Then they'd have you count aloud
from 138 backward by
sevens for a few moments.
They say, what were the words?
And you give what you can.
Then they give you a plum,
apricot, and lime, count
backwards by sevens.
Melon, lemon, we can see
all of these are
from the same category.
And then they switch
the category.
So we said, typically,
background knowledge helps.
But here's the way it can
get weirdly not helpful.
So here's the performance
of healthy young
people doing this.
So this is percent correct.
Good is high.
The first list, they're
really good.
Occasionally they forget
one of the three words.
But looks what's happening as
they go along for the second
list and the third list.
They're getting worse
and worse.
That's proactive interference.
The experience in the first
list is messing you up to
learn the new information
in the second list.
And most of the errors people
make are substitutions.
They go plum, apricot, apple.
By the third list, they're
going melon, lime, apple.
Do you see what's happening?
Because they're related, because
they're related, now
you're getting confused.
If I heard the word grape
recently, was that in the
first group?
I'm not reporting that
one right now.
Was it in the one before that
or the one I'm supposed to
report right now?
The relations among them mess
you up because it's hard to
tell when you heard them.
And they're all related.
And just to convince you that
it's true, because you might
say well, maybe you're just
getting tired like list, and
list, and counting.
Then they give you a new list.
And look what happens.
If it's fruits, still fruits,
you're still stuck.
But if it's another list like
vegetables, flowers, and
meats, or professions,
very different.
Your memory zooms
right back up.
Because all the interference you
had here about fruits is
no longer relevant for learning
a set of professions.
And it's kind of
graded, right?
We think the flowers as more
related to fruits kind of.
And professions is very
unrelated, doctor, lawyer,
programmer.
The more unrelated it is, the
more your memory goes right
back to where it was.
Because the proactive
interference
is no longer happening.
Another thing that researchers
have focused on as we read
things, what do we focus on?
So here's an example where they
read people sentences.
And then they tested them either
for the meaning or for
the style of the sentence.
Usually when we read stuff,
we're focused on the meaning,
not the style.
Style, we might notice it.
But usually, what
am I reading?
What's the point?
If they weren't unwarned,
they read the sentence.
Then you're tested.
It's much better for meaning
than for style.
Because we automatically
go for meaning.
That's what we go for when
we read by and large.
When we think about poetry
or something,
that might be different.
But reading typical text,
what's the meaning?
We strip away, almost,
the style.
We want to get to the content.
And they're terrible if they're
asked about the style
or the specific organization of
the sentence, the word by
word organization.
But, of course, if they
focus on it, they
can do a lot better.
So this is just saying
that we naturally go
for gist and meaning.
And we try to throw away a lot
of the specific particulars
like the way the sentence
was organized, the
style of the writing.
OK.
So now I'd like to do a
demonstration that will work
better for some than others.
But here we go.
So here we go.
I'm going to read you
a list of words.
And then I'm going to ask you
for a couple different words
and ask you if they
were on the list.
OK.
Here we go.
Ready?
Door, glass, pane, shade, ledge,
sill, house, open,
curtain, frame, view, breeze,
sash, screen, shutter.
OK, was the word glass?
AUDIENCE: Yes.
PROFESSOR: Was the word
potato on the list?
AUDIENCE: No.
PROFESSOR: Was the word
shade on the list?
AUDIENCE: Yes.
PROFESSOR: Was the word
car on the list?
AUDIENCE: No.
PROFESSOR: Was the word
window on the list?
AUDIENCE: Yes.
No.
PROFESSOR: OK.
How many people said window?
Put your hands up.
I heard a lot of window.
All right.
You're not helping
me out here.
Smart undergraduates like you,
at the peak of your memory,
will about half the time
say yes to window.
You saw this demonstration
before, or
you heard it before.
The way they compose these lists
is they ask students to
say what's the first word you
think of that goes with door?
The second word?
And the first word that goes
with door, the most common
one, they'll put over here.
That's the trick word,
the lure word.
And then these are other words
that people think kind of goes
with the word door.
So if you hear this list, and
you're tested for did you hear
the word window or see the
word window-- it doesn't
matter whether you see
it or hear it--
about half the time
undergraduates will say yes, I
heard it or saw it.
Because they're getting
the gist of the list.
This is all about door
and window stuff.
So when the word window appears,
they have a false or
illusory memory.
The rate of false or illusory
memories goes
up with age as well.
For every decade that will
pass, you'll add
a few more of those.
But even undergraduates,
typically, about half the time
they'll falsely recall they
heard the word window.
Again, the idea is here's
this double-edged sword.
It's about words that go
with doors and windows.
That's the gist.
That's the main idea.
When you get the word window,
you falsely believe that you
saw it or heard it.
So that's the way that people
try in the laboratory to
create false memories that are
experimentally testable.
We'll talk about real life
ones in a moment.
So we said all these things make
it feel like memory is
more the punch bowl metaphor
than the camera.
Because it's all swished
together, the proactive stuff,
the interpretation, the
retroactive changes that are
created in memory are all
altering the memory based on
the interpretation or based
on subsequent experience.
So let me stop for one moment
to tell you, OK,
so memory is shaky.
Wouldn't it be cool to have
truly photographic memory?
I mean, that would be awesome
as a student.
It wouldn't be bad in life.
There's only been one
well-described case of a
person who seems to have truly
photographic memory.
You hear various stories.
Most of the people who are
things like memory performers,
or there's memory Olympics and
things like that, they train
the heck out of themselves to
use different methods that can
enhance your memory.
And they can do amazing
things.
But it's all hard work.
It's all hard work as far
as we understand.
But here's a guy who was
different, studied by Luria, a
psychologist in Russia,
about 100 years ago.
So this is a guy who was a
reporter at a newspaper.
And he would go out and come
back and type up the report of
what he had seen at some event
for the newspaper.
And the editor noticed that
this guy never took notes.
He came back and just
started typing.
And the editor said, you've
got to take notes.
Because you won't know exactly
what happened,
who said what exactly.
You'll make mistakes.
The guy said, no.
I'm always perfect.
The editor said, OK.
We're going to teach you
a lesson about this
just to show you.
He got some material.
He said, everybody
come around.
He's going to embarrass
the guy.
I'm going to read
you something.
You tell me every word I said.
He read him some gibberish.
And the guy repeated every
word perfectly.
This guy truly had photographic
memory.
And kind of interestingly, when
they said, wow, you have
photographic memory.
He didn't go, yes.
I'm awesome.
I'm a superhero.
He said, doesn't everybody?
He was not aware that most of us
don't remember every single
thing that we study easily and
for the rest of our lives.
So he would be presented rows
of digits like these, study
them for three minutes, and he
could recall them days, weeks,
and months later perfectly.
This is almost the only case
we have well-described and
well-analyzed.
So it's really rare.
He would say when he had to
think back at a particular
list, like tell me the one from
last year, or tell me the
one from two years ago, he would
have to think where he
was and reinstate.
So that in his mind's eye, he
would see the room or hear the
voice of the person
reading it to him.
But even 15 years later,
perfect memory
for a list like this.
Wouldn't you like to have
that right now?
I wouldn't mind it either.
He also was synesthetic.
That is, when he heard things in
one modality, it triggered
perception like experience
is another modality.
He could change his resting
pulse from 70 to 100.
He could change his temperature
by two degrees by
force of will.
He's an unusual person.
We would love to discover
another person like this in
the place of the planet.
We have not seen another
one well-documented.
Probably there is.
But they're sitting somewhere
in some village remembering
everything perfectly going, I
thought you all remembered
everything perfectly.
So you could think, wow,
that's awesome.
That's a nice superpower
to have.
But he was not a happy person.
This is kind of an interesting
question.
Because he complained that when
somebody spoke to him
like a family member, what would
happen was he would be
flooded by a word with some
memory for some list or some
event last week, last month,
or 10 years ago.
His family members said, you're
not listening to me.
Yeah, because every word
triggered back or brought back
a flood of memory.
He got so miserable that things
in his environment
would trigger perfect floods
of memory into his mind--
and this is truly
like a novel--
at one point, in order to get
rid of memories-- and this did
not work-- he wrote them down on
a piece of paper and threw
them into the fire thinking
somehow that would work.
So this is one of these Twilight
Zone, O. Henry kinds
of stories where you think
it's awesome to have
photographic-like memory.
But, in fact, it seems to have
blocked, in many ways, his
development as a person.
Once he realized he had such
a rare memory, he became a
professional memory performer.
And then all kinds of jobs and
finally retreated into a
countryside kind of unhappy,
treating people with herbs
with his wife and son.
He did not have a happy,
awesome life.
I don't know if in this world
he would do better?
Because you could get on TV
shows and become a celebrity
or something if you
could do this.
So what's the problem with
photographic-like
memory do you think?
Why is it that we kind of wish
we had it at certain moments?
But what's the drawback?
Well the drawback seems to be,
imagine if you had in your
head a photograph
of everything.
You would have so much stuff
that you wouldn't be analyzing
it for the basic point
of what it's about.
So we just said, the risk of
analyzing things for their
basic point, their basic gist,
is that we want to get the
bottom message.
And we give up a lot
of the particulars.
It's not like a photograph.
It's like a very small abstract
or a note about a
photograph that's
in your mind.
But that's a very powerful way
to approach the world.
Because then all your background
knowledge is
instantly available to help you
interpret what's going on.
Because you're using lots of
connections and very few
particulars.
Too many particulars are as
burdensome as probably having
too many generalities.
Let me talk a minute about
flashbulb memories.
So this is a kind
of funny thing.
You might have the experience
in your own life of very
salient moments, big moments in
your life with your family,
other things you're doing in
your life, where you say, I'll
never forget this moment.
Because just everything
is so vivid for me.
People call this flashbulb.
We can never know how accurate
your flashbulb memory is.
I'll never forget when I got
into MIT, the moment.
Because I was wearing
my lucky socks.
And it was sunny outside.
And you might be right,
or you might be wrong.
So there's a slightly gruesome
research enterprise which
takes public events that are
very emotional for people.
So some of them will be very
historical for you somewhere
in your lifetime.
John F. Kennedy's assassination,
the Challenger
blowing up as a high school
teacher was going up to be the
first high school teacher
to do that.
The O.J. Simpson verdict, were
you even alive for this?
I can tell you that got an
unbelievable amount of interest.
Because I'm from Buffalo.
That's where O.J. Simpson
played football.
So I have a particular
interest.
It was like everything you
wanted in a TV show.
Tragically, two people died.
Because O.J. Simpson is a super
famous football player,
there was huge debate about
whether he had murdered his
wife and another person
in the house.
And there was an exact
moment when they
said, get on your TVs.
Here comes a verdict.
Or the 9/11 attack.
So here's this funny
research business.
What people do is they go.
And as soon as these horrible
things happened, they ask
people to write down where were
you, what were you doing,
how did you learn about it, what
were your feelings, what
were the feelings of the people
around you, and what
did you do in the next hour?
You can't be prepared for
this other than wait
for something horrible.
Everybody says, I'll never
forget where I was when 9/11
happened or things like that.
People feel that way.
And they certainly remember that
day more in some sense
than a typical quiet day.
But here's what they do.
They test them on their
own answers.
So you gave the information
just a little bit after.
Presumably, it's roughly
correct.
If you're tested a year later,
yes, you remember that day
better than other days.
But it's full of errors.
It's full of errors.
And people are way
overconfident.
They say, I know where
I was a year later.
And I know I was with
my friends.
And you say, a year
ago, you wrote
down you were by yourself.
Oops.
But I'm pretty sure I was
wearing my raincoat.
And you go, oops, you
wrote down you
were wearing a sweater.
Oops.
Your memory is way higher.
But it's full of inaccuracies,
even though people
are sure it's not.
They're sure that's
not a inaccurate.
So the next horrible public
event that happens, there will
be a bunch of memory researchers
running around.
And they'll be saying,
where were you?
What were you doing?
What were you feeling?
Because we need that to be able
to verify whether your
memory for emotionally intense
experience is accurate or not
and how long it lasts.
A couple of experiments
and then a video.
So here's eyewitness
testimony.
There's nothing more dramatic in
court on the TV shows or in
real life, if you have to
be around these things.
Where the person says,
who was a person who
murdered your neighbor?
And you go, that's the woman.
That's the man.
And the jury's looking.
So how accurate is eyewitness
testimony?
Of course it has to be
somewhat accurate.
We're not living in a crazy
world where people are
randomly imagining things.
But how accurate is it really?
So here's a kind of an
experiment they did.
This is work from Elizabeth
Loftus who's a
leader in this area.
She would have people
just see slides--
this is before computers,
basically--
where a sports car would come
to an intersection, would
turn, and would hit a pedestrian
in the slides.
So it's not the drama
of really seeing it.
It's a stage thing.
And it would be either a yield
sign or a stop sign just
before the car turns that
you would clearly see.
And let's pretend you were in a
condition where you saw the
yield sign.
Then afterwards, they would say,
did another car pass the
red Datsun while it was stopped
at the yield sign?
That's consistent,
the world yield.
Or did another car pass the
Datsun while it was stopped at
the stop sign?
See you slipped in
the word stopped?
Or in neutral, you don't
say anything.
And now you say, which
slide did you see?
You show them the actual
slide with a stop
sign or a yield sign.
You saw the yield sign.
But here's what happens.
If you saw the yield sign, and
you are shown this yield sign,
you do pretty well,
consistent.
Look what happens if you
saw the yield sign.
You've got the question, did
you see a stop sign?
And now you're tested, what
did you actually see?
You're pretty much wrong.
You're pretty much saying,
I saw a stop sign.
That's retroactive
interference.
You saw the yield sign.
You were asked about
a stop sign.
And now you believe you
saw a stop sign.
That's why it's so important
how police or other people
interrogate witnesses.
Because if they slip in certain
words, people have a
hard time going back to
the original memory.
They'll have a memory that's
a mixture of the original
experience and the questions
asked about that experience.
So people say, oh that's just
a laboratory experiment.
In real life, that
wouldn't happen.
So they did this experiment.
Jim, a graduate student,
reminded his younger brother
Chris that they lost Chris in
a mall when Chris was five,
and an older tallish man
brought him back.
So that would be a pretty
traumatic thing for a
five-year-old to be lost in
a mall and have an old
man take you back.
Certainly for the parents,
you're going where's the kid?
Where's the kid?
So two days later, Chris says,
the younger kid, yeah.
I was with you guys
for a second.
And then I went over to look at
the toy store, the KB Toys.
And then we got lost.
And I was looking around.
I thought, I'm in trouble now.
And then I thought it
was never going to
see my family again.
I was really scared.
And this old man, I think he
was wearing a blue flannel,
came up to me.
He was kind of old.
He was kind of bald.
Chris was never lost.
Jim, the graduate student,
being mean to his younger
brother, but for good science
reasons, told
him this slight story.
He didn't give him any
of these details.
He just said remember when you
were five years old and got
lost in the mall, and the old
tall man brought you back?
But what's happening is our
memories of when we're kids
are pretty vague.
Chris is sort of mixing in some
real things that happened
in the story.
And he's fabricating.
He's not trying to get
away with anything.
He's just creating this
false memory.
And he said, oh no.
We want it even more
lifelike than that.
So here's the experiment
they did.
They had 120 students see
an ad for Bugs Bunny at
Disneyland to evaluate the ad.
So you're brought into a room.
They say, we want to market test
whether this is a good ad
for Disneyland.
All these people had been to
Disneyland some years ago with
kids in real life.
Then they said, by
the way we're
thinking about Bugs Bunny.
When you were there,
did you meet him?
Did you shake his hand?
Now, what's the big trick
about Bugs Bunny and
Disneyland?
I saw some smiles right away.
Bugs Bunny is one of the few
cartoon characters that many
kids know that's not a Disney
character and, by law, cannot
be found at Disneyland
or Disney World.
But one out of three college
students remembered seeing
Bugs Bunny at Disney World or
Disneyland when they were a
kid after they had just seen
some promotional material
showing Bugs Bunny
shaking hands.
Because they had been there.
They don't remember stuff.
OK.
Bugs Bunny, sure.
How potent is this way that we
mix up new information with
the original experience.
So we can't tell apart the
original memory from the mixed
up new relevant information.
I mean, this would not have
worked, of course, if they
show you King Kong.
You'd be like, there's no
way I saw King Kong.
It has to be slightly
credible.
But it's a pretty big difference
in some cases.
So here's one example
in real life.
This is a real case.
In a dark, October night, a
man picks up on Pacific
Highway, south of Seattle,
hitchhiker.
It turns into an
isolated road.
The man brutally rapes
her and leaves her by
the side of the road.
24 hours later, she looks at
an array of photos, and she
picks out a man who
was convicted.
Because she says, that's the
man who brutally raped me.
A few months later, another
man was arrested
for a series of rapes.
She sees his picture in
the newspaper, and
she realizes oops.
Sadly, this is the man who
attacked and raped me.
He's released from jail.
By then, he's lost his money,
his job, his fiance, his
reputation.
He spends four years
pursuing a lawsuit.
He dies 11 days prior
to the trial.
10 months later, his estate gets
$2.8 million because the
police weren't very careful how
they did the photo lineup.
It turns out if you look at the
photo lineup, his was a
slightly outlier picture
of the six pictures.
So the woman went
for that guy.
So when she's accusing
him in court, she's
not trying to lie.
what's she mixing up?
Her memory for the photo array
versus for memory for the
original event.
Those two have gotten
blended in the
punch bowl of her memory.
Does that make sense?
Perfectly with good intention.
And there's 80,000 trials
you estimate the rely on
eyewitness testimony.
And many, many of those
are mistaken.
It's just human nature to
mistake them, especially
because trials are not boom
one minute later.
There's lots of discussion,
lots of interviews with
policeman, or prosecutors,
or lawyers.
Lots of things happen from the
original crime moment until
that moment in court.
Every discussion, and thought,
and feeling you have from the
original experience blends in
with the original experience.
And it can be hard to
pull those apart.
Here's another sort
of weird example.
A woman at home in Australia,
she's brutally
raped in her home.
She identifies Donald Thompson--
now you'll see why
this is a bit ironic
and a weird story--
a renowned Australian
psychologist who studies
eyewitness memory problems.
It turns out he was on
television at the moment that
she was being raped.
And, obviously, she's in a very
disturbed difficult moment.
And so she conflates the face on
the TV with the face of the
actual horrible perpetrator.
So he has a good alibi.
He's on TV somewhere.
But in a perfectly good way,
she's trying to be correct.
These things get jumbled
together.
So you're going to see
it in one minute, a
film of Susan Nason.
This is an amazing story.
Sorry.
You'll see the film of
Eileen Franklin.
But Susan Nason was an
eight-year-old girl.
She was missing and found
murdered in October 31, 1969.
20 years later, Eileen
Franklin-- you'll see later--
remembers that her father
murdered Susan Nason.
She testifies against him,
and he's found guilty.
And he goes to jail.
He's been subsequently
released.
Because she says I was
with him when he
murdered my little friend.
But she doesn't remember
continuously.
She remembers it because a
therapist has had her think
about her past.
And all of a sudden, what she
feels like was a repressed
memory comes back.
So we're going to show a
movie about this topic.
It's your next paper topic.
What's the status of memory?
So let's separate two things,
because it's really important.
Cases where women or men--
more often women--
remember being abused, sexually
abused, remember it
all the way through.
That may not like to
think about it.
But they remember it all
the way through.
That's not what we're
talking about.
What we're talking about are the
rare cases where a man or
a woman says, I haven't
thought about this.
I feel like I've repressed
this for 20,
or 30, or 40 years.
And now, more often than not
because of working with maybe
a psychologist or clinical
psychologist to help me with
problems I have, I recover
my repressed memory.
And it's a brutal thing.
Because you can imagine on the
one hand, you have a young
woman accusing her father, or
uncle, or the father we'll
say, of doing something that we
think is terrible, which is
sexually abusing her, the
biggest failure of trust you
can have in a father,
a huge violation.
So he's horrible
if she's right.
But if her memory's inaccurate,
what's more
horrible than an innocent man
being accused by his own
daughter of sexually
abusing her because
her memory's incorrect.
So what we'll show you
two films briefly.
So the father went to jail.
The lawyers who were defending
the father wanted to tell the
jurors the following thing,
which in every account you
read is accurate.
That everything that she
described about the death of
that girl, Susan Nason, every
detail she described was in
the newspaper accounts
of the time.
And that no detail that she
provided was verifiable and
different than newspapers had
reported at the time.
One of the things that people
like to do, investigators, is
have the person know something
that wasn't publicly released.
And everything that she spoke
about in regards to the little
girl's murder, Susan Nason's
was publicly available
information that had been on
television or in newspapers.
And the judge originally
ruled that the jurors
could not be told that.
And then later on, they
retried the father.
And the jurors were told that.
And the Father was
let go from jail.
So there was this huge
pendulum swing.
Because, originally, as these
repressed memory cases were
brought, people wondered, well,
why would the woman lie
about such a horrible thing?
It's so horrible.
Of course she must be
telling the truth.
And of course the father must
be lying to protect himself.
But now, especially in the
context of repressed
memories-- again, very different
than continuing
memories, the ones that are
recovered after decades--
there's a suspicion that some
of them might be inaccurate.
And some psychologists working
with some patients might be
having patients think about
possible sources of their
difficulty.
And these memories get
falsely constructed.
And the hard part, and the part
that you'll write your
paper about, is knowing
which is which.
Because it's heartrending.
It's heartrending to have
a woman who was
abused be not believed.
It's heartrending for a father
who was not an abuser to be
accused of being an abuser.
And it's incredibly hard to
have direct evidence about
who's telling the truth and
who's not in these kinds of
cases that are so far from when
the crime occurred or
might have occurred, and where
there's such a long period of
nondiscussion about it
because it's been
repressed for decades.
So you'll look at that.
It's a big task.
It takes you into courts.
It takes you into clinical
complexities of people.
