- Welcome everyone to
Wednesday Nite @ the Lab.

I'm Tom Zinnen.

I work here at the UW-Madison
Biotechnology Center.

I also work for the Division
of Extension Wisconsin 4-H.

And on behalf of those folks
and our other co-organizers,

PBS Wisconsin, the Wisconsin
Alumni Association,

and the UW-Madison
Science Alliance,

thanks again for coming to
Wednesday Nite @ the Lab.

We do this every Wednesday
night, 50 times a year.

Tonight, it's my pleasure to
introduce to you Haley Vlach.

She's a professor here

in the Department of
Educational Psychology

and our School of Education.

She was born in
Portland, Oregon,

and went to high school at
Mountain View High School

in Bend, Oregon.

And then she went to
Carnegie Mellon University

in Pittsburgh and studied
business administration

and psychology.

Then she moved back west

to go to the University of
California at Los Angeles

for her master's degree and PhD,
both of which in psychology.

Tonight, she's going
to be talking with us

about forgetting, what it is,

and how it helps us remember.

Pretty fascinating topic,
a paradox.

Please join me in
welcoming Haley Vlach

to Wednesday Nite @ the Lab.

- Thanks for that introduction.

I'm very excited to be here

and to speak with you all
about some of the work

that we've been doing in my lab.

I'm Director of the Learning
Cognition and Development Lab.

And in my lab,

we're really interested in how
people think and learn.

We spend a lot of time
thinking and learning

about thinking and learning.

And in particular,

we're interested in
cognitive development.

That is, how does thinking
change across the lifespan?

We're particularly interested
in thinking and learning

during childhood, but we
also study adults as well.

And we spend a lot of our time
thinking about memory

and memory changes and how
those changes in memory

might contribute to our
thinking and learning.

And we're really
interested in memory

for a number of reasons.

So the first reason

is that it's theoretically
very interesting.

Like how does memory work?

We take in a seemingly
infinite amount of information

from the world
and somehow manage

to decode that
information, store it,

and then retrieve it
later when we need it.

And so that process
is still a mystery

and is very motivating to study,

just coming up with a
theory of how memory works.

Memory is also practically very
important for many reasons.

So first, it's important to
our day-to-day functioning.

So for instance, when we're
going to the grocery store,

we need to remember the things
on our shopping list.

And we often think in our mind,
"Hmm, do I need more milk?"

And you have to remember
whether or not

you have milk in the
fridge currently.

There's also many ways
in which memory

can be implied into training,

educational and
health interventions.

Memory is at the core of
allowing us to think and learn,

as we will discuss more today.

And so there are
numerous applications.

But on a more sort of
spiritual or emotional level,

memory is fascinating
because it's what defines us.

In other words,
we are our memories.

When we create
our sense of self,

we think back to all
of our experiences,

and what those experiences are,

are the memories that
we've stored in our brain.

So memory truly serves
at the foundation of the self.

So there are many, many
reasons to study memory.

One thing that is
very interesting

to most people who are learning
about memory for the first time

is that remembering is not the
most common part of memory,

but instead the most
ubiquitous process in memory

is the fact that we forget.

Today, what I'm going
to do is I'm gonna first

provide an overview
on forgetting.

What is it and what do
we know about forgetting?

After that brief introduction,

we're gonna dive into
talking about forgetting

helping us to learn.

And this is counterintuitive
as we will discuss,

because normally we
characterize forgetting

as a process that deters memory.

And then finally, I'll end
with some concluding thoughts

about where we can go and how
we can think about forgetting

in our day-to-day lives.

So first let's dive in,

let's talk about
what forgetting is

and how scientists
think about forgetting

when we study it from a
scientific perspective.

Forgetting is operationally
defined as the declining ability

to retrieve information
across time.

And what you can see
here in this image

is on the X-axis is time.

So number of days or a month,

and then on the Y-axis,
you see this equation,

and this equation is
called a saving score.

And you can think about
this as the percent

that is recalled across time.

And what you can see is that
the nature of forgetting

is such that soon
after learning something,

we have pretty
good memory for it.

But over time, that ability to
retrieve the memory declines,

and it declines according to
what we call a forgetting curve.

Okay, so the curve is
fast-changing at first,

but then over time slows down

and gives sort of a
U-shape to the curve.

And we've been
studying this process

for a considerable
amount of time,

dating back to the late 1800s

at the birth of
psychological science.

So because forgetting has been
such a well-studied process,

we know some things about it.

And I'm gonna give you a brief
overview of what we know.

So first, we know that we
forget across the lifespan.

So forgetting happens
in young infants,

in adulthood, and
in older adulthood.

In other words, every stage of
life, we observe forgetting.

The next thing that we
know about forgetting

is that forgetting happens
across tasks and timescales.

And it's a very
predictable pattern.

And in fact, that pattern is
what I just showed you earlier,

the forgetting curve.

Now in this figure,
what I have here

are two different graphs.

On the left side of the screen,

you'll see that the
X-axis indicates time

as a matter of seconds.

However, on the right side,

there's a different
dimension of time,

which is years, like 0 to
50 years in particular.

And then on the
Y-axis for both graphs

is the percent correct.

That's the percentage
remembered.

And what we can see

is regardless of whether
or not the timescale

is a matter of seconds as
such in the left graph,

or a matter of years,

such as what we see
on the right graph,

we see the exact same pattern,
that forgetting curve.

Now, for those of you that
are mathematical buffs,

what you can see is that
what is charted here

is a power function.

That's that equation at
the top of the graphs.

And indeed, forgetting
follows a power function

with a high degree of fit.

So those are squared values,

or what you're seeing
is like the percentage

at which the power function
can account

for the data that we
observed via forgetting.

And one thing that's
fascinating about forgetting

is that one of the things

that we can mathematically
model the best

of human cognition.

Indeed, capturing about 88% or
90-some percent of the variance

is very high.

And so forgetting is very
predictable across timescales,

but also across tasks.

We see the similar forgetting
curves across tasks.

The next thing we know
about forgetting

is that we can
observe forgetting

on multiple levels of analysis.

In other words,
we see forgetting

on the level of an individual
neuron in our brain,

but we can also
observe forgetting

in complex human behaviors,

such as those day-to-day
functions that we engage in,

especially more complex things

like learning new concepts
in the classroom.

So we're seeing forgetting
at multiple levels

of our being as humans.

We also know that
we're not alone.

Humans are not the
only ones that forget.

We can observe forgetting
in other species,

even organisms that don't
have our nervous system.

So for example,
in very simple organisms

that only have a
matter of cells,

we observe that those
cells will forget.

So forgetting is not something

that's specific to
the human experience

or our nervous systems;

it's much more widespread
across organisms.

Okay, so at this point,

what you were probably
thinking is that,

"Wow, so what you're telling me

is that we're forgetting
everything all the time."

And that's right.

We are forgetting
everything all the time.

It is predictable
and it's inevitable.

So why does this happen?

Why is this happening
to us all the time

in a predictable manner?

Well, the truth is,
is that we don't know.

It's a scientific mystery.

We don't know what
causes forgetting,

but currently, there
are two primary theories

about why it is that we forget.

The first collection of
theories focus on interference.

In other words,
these theories posit

that because we're
continually acquiring

more and more information,

that that new information
blocks us from retrieving

the old information
in our mind and brain.

So if we weren't to
learn anything new,

we wouldn't forget,

is essentially what
they're arguing.

However, there's a different
collection of theories

that center on time and the
properties of the universe

with regards to energy.

So according to these theories,
the reason that we forget

is that energy passes
across biological membranes

according to this power function
that you've seen earlier,

in other words,
the forgetting curve.

And because of that,

we observe forgetting at
different units of analysis,

like a single cell, but also,

that scales up to complex
human behavior as well.

Now, one issue is that we can't
control for time and energy.

In other words, we can't
put people in a vacuum

where they're not
experiencing time

in order to understand whether
it's truly interference or time.

Moreover, we can't control time

when we're doing
interference studies.

So with additional learning
comes additional time.

And so the reason
that it's a mystery,

is it interference
or is it something

about the properties
of the universe?

We just may never know

because we can't put
ourselves in a vacuum

in order to control
these two variables.

So the debate rages on,

but we're pretty sure that
it's either interference,

time, or some
combination of the two.

Okay, so that was the
overview of forgetting,

what it is and what
we know about it.

Now I'd like to move on and
I'd like to tell you more

about why forgetting is
actually a good thing,

because at this point
you might be wondering,

"Well, if it's
inevitable, predictable,

"and gonna prevent us
from remembering things,

it must be bad."

Well, it turns out that
that's not the case.

Forgetting can be used
to help us remember.

So if forgetting is inevitable,
how do we remember?

This has been a central research
question for many years.

And what researchers
have discovered

are that certain
learning environments

or conditions of the environment
can actually improve our memory.

They can help us to
retrieve information.

One of the most
well-studied conditions

of the learning environment
is called spaced learning.

And what scientists
have observed

is that when we distribute
learning events across time,

people have better memory
for that information

compared to it being massed
in immediate succession.

So here's a real life example
of that.

Imagine that you are
studying for a test.

You have one or two options:

you could cram the night before
and just cram, cram, cram

right up until the test.

Well, that behavior would be

studying in immediate
succession.

We would call that
massed learning.

The other option is to
distribute your learning

during the week and study
a little bit every day.

So you might study a
little bit on Monday,

a little bit on Tuesday,

a little bit on Wednesday
and so on and so forth,

building up to the test.

And what you may
experience if you cram

is that you do okay on the test,
you do well enough,

but a few days later
you might say,

"Wow, I don't remember anything

from the test that I took
earlier in the week."

However, if you had
distributed your learning

or spaced it out across time,

you would probably
experience more memory

for what you studied for.

In other words, you'd
actually remember

what you were studying.

And that's a real life example
of how spaced learning

promotes memory to a greater
degree than massed learning.

In the lab, scientists
do this kind of work

using word lists.

What they do is they present
words to participants

one at a time.

So what you're seeing
here on this list

is a series of words,
and what you'll notice

is some of the words
like the word cat

are presented in
immediate succession,

one right after the other.

Whereas other words on the list,
such as the word dog,

is distributed across time.

You'll see the word dog,

and then you'll see
some other words

and then the word dog
will come back.

The consistent finding
across these studies

that use word lists
is that participants

have stronger memory for the
words distributed across time,

like dog, relative to the
words that are massed in time,

like the word cat.

We know from over a
thousand published studies

that spaced learning
promotes memory.

It's a highly
replicable phenomenon

that's been studied
across many timescales

and many contexts.

One of the primary reasons

that spaced learning
supports memory

is actually that
we're forgetting

during the learning events.

So let me briefly
describe why this happens.

So in between each
spaced learning event,

you'll forget information.

And what that forgetting does

is it makes it harder to
retrieve what you've learned.

But at subsequent
learning events,

what you'll do is
you'll retrieve

your prior information
from memory

and the cognitive effort
that you engage in

in remembering that information

will then be translated
into a slower forgetting

for that information.

In other words,
by trying to remember

and practicing that retrieval,

you'll then have a slower
forgetting rate in the future.

And so by engaging in that
retrieval practice

across distributed
learning events,

you're actually
slowing forgetting

and promoting your memory.

Now, researchers have
for a long time now

known that spaced learning
promotes memory

and that forgetting can be
manipulated to promote memory,

but this isn't true
for all forms of memory.

For example, researchers
have questioned

whether or not this
process of forgetting

is good for everything.

And in particular,
researchers have asked,

can forgetting promote
categorization

and concept learning?

And the categorization
and concept learning

is learning that things
share similarities

and differences in the world.

So for example, a golden
retriever is called a dog

and a wiener dog is
also called a dog.

Even though they
look very different,

they share similarities
and thus belong

to the category of dog.

And general intuition would say,

"Hmm, I don't know if
forgetting is good,"

because in general,
intuition tells us

that forgetting is not good,
that it's a bad thing.

However, even researchers
who are experts in this field

really argued that yes,

forgetting should
deter categorization

in concept learning.

It's really fun to go back
through the previous literature

and read old studies

because there's some
fighting words out there.

People really had strong beliefs

that forgetting would deter
conceptual development.

My favorite quote is
from Ernie Rothkopf,

where he argued that
things like forgetting

and spaced learning would
be the "friend of recall,"

so help us to remember,
"but the enemy of induction."

So in other words, it would
deter our ability

to learn categories
or learn concepts

where we have to abstract out
across our experiences.

Let me walk you
through this argument.

So imagine that
you're a young child

and you're learning
about the category

of bunny for the first time.

You'll see one bunny
in one context,

and then you'll see another
bunny in another context.

Then you might see a third bunny
in a different context,

and what you need to do

in order to learn
the category of bunny

is to abstract out the
similarities and differences

across these experiences.

So you might see that,

well, the bunnies
share the same shape.

And so maybe that's
a relevant feature

of the category of bunny.

However, there are other
features that vary.

So for instance,

the color of the hair is
different across these bunnies.

And a child might think,

"Hmm, I guess the hair color
is not a relevant category.

It's irrelevant to the
category of bunny."

And the reason that
children need to abstract

across these experiences

is they have to know
what to generalize

based on when they
see new bunnies

that they've never seen before.

They should generalize
based on body shape

rather than on something
like the color of the hair.

Now, Ernie and others
thought that the forgetting

would deter this process

because how are you
supposed to abstract

across all of your experiences

if you can't remember
your experiences?

So for instance, if you can
only remember the body shape

of one bunny you've seen before,

how are you supposed
to know that body shape

is a relevant feature
to the category of bunny?

You can't remember
that all the bunnies

shared the same body shape.

Same thing goes
for irrelevant features.

If you only see
one color of hair

and you don't see that it varies

across all the
different bunnies,

you might think that hair
is a relevant feature.

You know, the
first bunny you see

might be a certain color

and you would think
that that color

defines the category of
bunny when it does not.

So in other words, forgetting
should be bad for abstraction.

Now what's interesting is that
despite these fighting words

being out there and strong-held
belief by researchers,

no one had really tested it.

So what we decided to do
was to test this hypothesis,

and one of the most common
methodologies that we've used

to test this hypothesis

is called the novel
category induction task.

And this task is designed
for young children

who are learning words and
categories for the first time.

And what we do is we present
them with novel objects

and novel words to ensure
that they're learning

these objects and words
for the first time.

So just as an example,

an experimenter
might show children

a series of novel objects like
this and label them and say,

"This is a wug, this is a wug,
and this is a wug."

And then at a post-test,
present children

with a series of objects.

Some they've never seen
before, some they have.

So for example, they'd
seen a cat before.

And then it's the child's job
to generalize the category

that they just learned to a
new instance of the category.

So what the experimenter
would say is,

"Can you hand me the wug?"

And it would be the child's job
to pick up that novel wug

they haven't seen before that
shares a similar feature,

in this case shape, to the
objects that they saw

during learning.

So this is referred to as the
novel category induction task.

And today I'm gonna show
you two experiments,

Experiments 1 and 2.

And the participants in these
experiments were typically

developing two to two and a half
year-old children.

And again, we were
really interested

in how this process unfolds

when it's organically unfolding
a lot during development,

which is the toddler period.

They're learning lots of
words and new categories

during the toddler period.

We made very simple manipulation
on the classic paradigm.

And what we did in Experiment 1

is we presented children
with novel words and objects

on one of three schedules:
simultaneous, massed, or spaced.

I'm gonna walk you through

each of these presentation
schedules now.

In the simultaneous condition,

children were presented with
four objects at the same time.

They were all put on the
table simultaneously.

What the experimenter would do,
would label each of the objects.

So the experimenter would say,

"Look, this is a wug," and
point to the first object.

They would wait 10 seconds

and then point to the
second object and say,

"Look, this is a wug,"

wait 10 seconds and
so on and so forth

for all four objects.

Now in this condition,
forgetting is minimized

because all of the objects
are present to the child

at the same time.

And they keep hearing the
word wug over and over again.

So children don't have
to rely on their memory

to abstract out what are the
similarities and differences

among the objects.

They're all on the table
at the same time.

The second condition was
the massed condition.

And in this condition,

we presented children
with objects one at a time.

So the experimenter would
put an object on the table

and say, "Look, this is a wug,"

wait 10 seconds, take
the object off the table,

and then put it
back on the table

or put another object
on the table and say,

"Look, this is a wug,"

wait 10 seconds for the child
to play with the toy,

take it off, and then
put a third object on,

and so on and so forth.

So in other words, the objects
were presented one at a time.

Now in this case,

children need to rely on
their memory a little bit

to remember what
they've seen earlier.

Because they only
see one at a time,

they have to think back,

"Hmm, what were the colors
and shapes of the objects

that I saw earlier?"

The final condition was
the spaced condition.

In this condition,
what children did

is they also saw one object
at a time,

but instead of seeing them
in immediate succession,

like in the massed condition,
there were 30-second delays

between each presentation
of the object.

So what children would do
is they'd see an object,

the experimenter would put
one on the table and say,

"Look, this is a wug."

And then the experimenter
would take it away.

And there'd be 30 seconds
of irrelevant activities

like playing with Play-Doh,
putting stickers on paper,

anything to keep the kids
at the table and entertained.

After that 30-second
play period,

children would then be
presented with another object

and the experimenter would say,
"Look, this is a wug."

And that would happen
so on and so forth

for four objects in total.

Now what you can see
across these conditions

is that the only thing
that's being manipulated here

is the timing.

Either children see all objects
simultaneously,

preventing forgetting, or
they see them one at a time.

And what the spaced
condition does

is it introduces the most
forgetting during learning

because there are those
30-second intervals

between each presentation

that gives children the
opportunity to forget

in between each object.

And so they have to
think harder and harder

about what they saw earlier
in order to abstract

the relevant and irrelevant
features of the category wug.

Children were also presented
with a distractor item

during learning, and the
experimenter did not label this.

They would say,
"Look at this toy."

And it was presented for the
same amount of time

as the objects, 40 seconds.

And then there was
either a immediate test

or a test after a delay,
a 15-minute delay.

And the reason for this
difference across conditions

is that we were interested

in not only forgetting
during learning,

that's those three conditions
I showed you earlier,

but we were also
interested in forgetting

between learning and test.

And so immediate condition
prevents forgetting

from happening
between learning and test,

and a 15-minute delay introduces
the opportunity of forgetting

between the immediate
and delayed test.

So we're introducing forgetting

at different levels of
the learning process.

And then the test item
was very similar

to what I showed you earlier.

Children would be presented
with four objects,

and then it was the
child's job to pick out

a novel instance of the category
that they learned about.

So the experimenter would say,
"Can you hand me the wug?"

And it's the child's job
to pick up the wug

and place it into the
experimenter's hand.

Okay, what I'm going to do
is show you some results.

This is the results
of Experiment 1.

And what you're seeing on the
X-axis is the testing delay.

So either children being
tested immediately,

or a 15-minute delay,

and then on the Y-axis is the
number of correct responses.

So this is the mean number
of times

that children correctly handed
the wug to the experimenter.

So here's what we found
at the immediate test.

Children in the
simultaneous condition

significantly
outperformed children

in the massed and the
spaced conditions.

So if Ernie Rothkopf
were here, he would say,

"Look, I'm right.

"The condition that had the
least amount of forgetting

led to the most learning."

'Cause the simultaneous
condition at the immediate test

introduced no learning or no
forgetting during learning,

but also no forgetting
between learning and test.

So this would sort of prove
Ernie and others right

that forgetting does deter
conceptual development.

However, let's look at the data
from the 15-minute delay.

What we observed at the
15-minute delay

is that children in the
spaced condition

significantly
outperformed children

in the simultaneous
and massed conditions.

And you might wonder here,

"Well, wow, this
is an interaction,

"a completely different
pattern of results

of the delayed test."

And indeed, what we see here

is children that had the most
opportunities of forgetting

perform the highest, because
indeed the 15-minute delay

was the most amount
of forgetting

between learning and test,

and then the spaced condition
introduced forgetting

during the learning process.

So this is the exact opposite
of what Ernie would predict.

Here what we see is
that forgetting might be

facilitating abstraction
and generalization.

I'm going to jump to
Experiment 2 quickly

and just explain why
we did Experiment 2.

So in Experiment 2,

what we were interested
in is we said,

"Well, we think that
forgetting is happening

between learning events."

In other words, we think
that these 30-second gaps

introduced opportunities
for children to forget.

But what we wanted to know
is we wanted to have data

to actually show that the
forgetting is happening.

So what we decided
to do in Experiment 2

is ask children to retrieve
their learning during learning.

And here's how we did this.

So imagine children are in the
simultaneous condition,

they have four objects put on
the table at the same time.

And the experimenter would
label the first object and say,

"Look, this is a wug."

Wait 10 seconds and then point
to the second object and say,

"What is this called?"

They would wait five seconds,

and then regardless of
what the children said,

the experimenter would say,
"This is a wug."

And then they'd move
on to the third object,

and they point to it and they'd
say, "What is this called?"

They'd wait five seconds,

and then regardless of
what the child said,

they'd say, "This is a wug."

And they did that
for all four objects.

The same thing
happened in the massed

and the spaced condition.

Children would hear,
"This is a wug,"

on the first presentation.

And then on the
subsequent presentations,

the experimenter would
first prompt the children

to report the word by saying,
"What is this called?"

Wait five seconds and
then say, "This is a wug."

And what these retrievals did

is it gives us a sense
of how readily children

are retrieving information
during learning.

And what we predicted

is that children in the
spaced learning condition

would demonstrate
the most forgetting

because of those
30-second intervals.

Okay, here's some data
comparing the final test

from Experiment 1
and Experiment 2.

And what you can see is
we observe the same pattern

of results across experiments.

The bars are a little bit
higher in Experiment 2.

This is to be expected.

It's because children are
getting more retrieval practice

by us asking them,
"What is this called?"

And so they overall did better,

basically a retrieval
practice effect here,

but we see the same pattern,
that at the immediate test,

children do better in the
simultaneous condition,

but at the delayed test,

they do better in the
spaced condition.

Here, what you're going
to see are three bars

representing the overall
retrieval successes

in the simultaneous, massed,
and spaced conditions.

So that's what will be
on the X-axis.

And then on the Y-axis,

what you'll see is the mean
number of retrieval successes

out of 24.

So there were eight trials
with three retrieval attempts

on each, so that adds up to 24.

Here's what we found.

We found that children in
the simultaneous condition

had significantly
higher performance

than children in the
massed condition.

And we found that children
in the massed condition

had significantly
higher performance

than children in the
spaced condition.

And this is exactly
what we predicted.

Children in the
simultaneous condition

are having a lot easier time

retrieving the label
for the category

because they're not experiencing
the same degree of forgetting

as children in the massed
or spaced conditions.

And indeed, children
in the spaced condition

are struggling the most.

We took this same data
and we plotted it by time.

And just as a reminder,

what we did is we
had Retrieval 1

be at the second learning event,

Retrieval 2 was at the
third learning event,

and Retrieval 3 was at the
fourth learning event,

'cause on that first
learning event,

we labeled the object.

We said, "This is a wug."

And then asked them
what it was called

on subsequent learning event.

So on the X-axis, what
you're seeing here

is retrieval attempt 1, 2, 3,

which corresponds to
learning 2, 3, and 4.

And we wanted to know if
the nature of retrieval

changed across the
learning phase.

So what you're seeing here first

is performance for the
simultaneous condition.

And what you see as a
relatively flat line

across the three
retrieval tasks.

And what this suggests
is that children

in the simultaneous condition

are observing overall
high performance

that doesn't change much
across the learning phase.

The next line that you're seeing

is performance in the
massed condition.

It's a similar pattern

to children in the
simultaneous condition,

it's just lower.

So it's a little bit harder,

but there's no change
during learning

for children in the
massed condition.

However, we see something
fundamentally different

in the spaced condition.

What we observe is that the
first retrieval attempt,

children really struggle
to retrieve information.

In fact, it's not significantly
different than zero.

So essentially, when children

get to that second
retrieval attempt,

they kind of stare
at the experimenter

and they don't know what to say.

They're unable to
produce the word wug.

However, across the learning
phase, we observed performance.

So they get better and better
at retrieving the word wug

during learning.

So what this data does is
it confirms our hypothesis

that this paradigm
does introduce

different levels of
forgetting during learning,

but what this data also does
is it provides evidence

for a theoretical count
that explains

why forgetting is
promoting learning.

And what we have argued
is that forgetting

is a form of abstraction,
forgetting acts as abstraction

in order to promote
conceptual development.

So I wanna walk you
through now how this works.

So imagine that you're a child

and you're seeing a wug or a
new toy for the first time.

Well, you're gonna see that wug

and you're immediately
gonna forget

everything about that wug

according to the
curvilinear pattern

that I showed you earlier.

And here, what we see is
that forgetting curve.

So you'll see a wug,

and a certain amount
of time will go on,

and you will then
experience another wug

or another new toy that
shares the category label.

And what will happen
is that that new wug

will prompt you to recollect
information that is similar

to the information
that you saw earlier.

So in this case,

what is similar across these
two items is their shape.

And so what you'll do is
you'll retrieve the shape

that you saw earlier
and you'll engage

in cognitive effort doing so

because you've
forgotten about it.

And so you have to
dig through your mind

to find that information,
that past memory.

And what that
cognitive effort does

is it slows the
memory for shape,

which in this category
is the relevant feature.

Now that second object
won't cue you to recall

other types of information,

like the color or the
texture of the object

that you saw earlier,

because there isn't a
match across the items.

And so what that means
is that you'll continue

to forget that
irrelevant information,

the texture and the color
at the same rate as earlier,

when you first saw
the original wug.

And what you can see from
looking at this image is now

there's different
forgetting rates

for information that's relevant

and information
that's irrelevant.

Let's do another
demonstration of this.

So let's just say
that more time goes on

and a child then
sees yet another wug.

And what that third wug
is gonna do

is prompt children
to recall information

from the first and second wug
that's similar to that item.

And again, that similar
feature is shape.

And so what children will do

is they'll engage
in cognitive effort,

searching for that
shape information.

And what that cognitive effort
will translate into

is a slowed forgetting
for that feature shape.

So it's again, slowing
the forgetting.

However, features
like color and texture

are continuing to be forgot,

according to that
original forgetting curve.

So they're being forgotten
at a much different rate

than the relevant information.

And what we hypothesize happens
across early development

or learning about something
new for the first time

is this process of
where we continually

re-retrieve relevant
information in the world

and then we don't re-retrieve
irrelevant information

in the world.

And as this process happens
over and over and over again,

we end up with different
forgetting curves

for information that's relevant

and information
that's irrelevant.

And so by the time
children or adults

need to generalize to
something new in that category,

they will more readily
retrieve relevant information

like shape, compared to
irrelevant information

like color and texture.

And this will support
generalization

and conceptual development

because they're re-retrieving
what's important

and then applying it
to that new category.

So in other words, it's
helping children, adults,

everyone to abstract what's
relevant in the world,

and therefore helping us to
learn categories and concepts.

Just as a quick summary.

For a long time, going
back to the 1800s,

researchers and general
intuition told us

that forgetting should deter
conceptual development.

It should prevent us from
abstracting what's relevant

and irrelevant in the world.

However, my lab's work
has shown the opposite:

that forgetting can actually
act as a form of abstraction,

speed up abstraction,
and help us to learn

new categories and concepts.

And so while we've always agreed

that forgetting can help
learning and memory,

we now know that it can
help us think and develop

our most higher order
forms of learning,

like learning a new language
or learning complex concepts.

So that's the silver lining,

is that even though forgetting
is inevitable and predictable

and will prevent us from
remembering information,

it's also gonna help us.

It's gonna help us
remember what's important

so that we can generalize
across our experiences

based on the
important information.

So I have a number of
concluding thoughts

that I'd like to share
with you all.

The first concluding thought

is to share some of the
exciting work that we're doing,

trying to build off this
basic research

to design interventions
for children.

One of the things that
we've done is we've thought,

"Well, why don't we integrate
forgetting into curriculum?"

In other words, we should
work with teachers and parents

in order to get
them to encourage

their children to forget.

Now, I know this sounds
very counterintuitive

because wow, teachers are
trying to help kids remember,

parents are trying to
help kids remember.

But remember, forgetting
can help us to remember.

So what we've been doing
is we've been working

with classrooms and teachers

and helping teachers to
integrate spaced learning

into their curriculum.

Here's a quick example.

In a lot of early
childhood curriculum,

teachers use units.

So they might have a lion month
or a flower month,

where they talk
about the same thing

in extensive conversation
for a month and then move on.

So in other words, it's
an immediate succession.

It's kind of like cramming.

So instead, what we've done
is we've encouraged teachers

to distribute lessons
out across time.

We've done a series
of experiments

to provide empirical evidence
for teachers

that this is a good thing to do.

So for example, in some
of our studies,

we come up with different
learning schedules

for science curriculum.

And the example that
I'm gonna show here

is the context of children's
science curriculum

about food chains.

And food chains
are a perfect context

because what teachers do is
they introduce food chains

across different biomes.

So they'll introduce the
food chain in the grasslands

and then the desert.

And then what they
expect children to do

is to abstract out across all
these different biomes

in order to generalize
to a new biome,

like the Arctic or the swamp.

And so what we do is we work
with classrooms and teachers

and develop a schedule such
as the schedule you see here,

where there's one of three
presentations options.

There's a massed schedule,
a clumped schedule,

and a spaced schedule.

What you'll see in the
massed schedule

is that lessons
about food chains

are presented
in immediate succession,

just like we do in the
lab with the word lists.

The spaced condition
distributes all the lessons

out across days of the week

so there's time in
between each lesson,

which maps onto the
spaced schedules

that we use in the lab as well.

In these studies, we use
an intermediate condition

called the clump condition,

which introduces a combination
of massing and spacing.

So some of the
lessons are presented

in immediate succession,

whereas other lessons are
distributed across time.

And we have each lesson be
about the same amount of time,

so that we control for time
across these experiments.

And we have a test for
children that happens one week

after their last lesson

to understand what they remember
from the varied conditions.

And I'm gonnashow
you some data here,

where we had two
different types of tests,

a simple generalization
or simple concepts.

This is things like learning
that bigger creatures

typically eat smaller creatures.

And then we also had
some complex concepts.

And the idea that we tested here
was the idea of interdependence.

So in other words,

if something happens to a
particular creature in a biome,

it affects all the
other creatures.

So for example, if there are no
more fish in the ocean to eat,

that affects all the
other creatures

that live in the ocean.

They will have less to eat
because there are no more fish,

especially creatures higher up
on the food chain.

So that's what you're
gonna see on the X-axis.

On the Y-axis,
what you're gonna see

is the difference between the
pre-test and the post-test.

So we gave the tests before
learning and after learning.

And what you'll see is for the
simple generalization

or the simple concept,

we found that children
in the spaced conditions

significantly outperformed
children in the massed

and the clumped conditions.

And this is what we expected
from prior research.

We expected to see
this based off of

the relatively
simple categories,

like the wugs that
you saw earlier.

In this work, it was actually
our first time testing

whether or not we would
find this phenomenon

in a more complex task, like
learning about interdependence,

but let me show you the results.

Here they are.

We found the same pattern.

We found that children
in the spaced condition

significantly outperformed
children in the clumped

and massed conditions.

So what these
classroom-based studies do

is they help teachers
to understand

how they can
manipulate forgetting

by using spaced learning
in their curriculum

and in their teaching practices.

And indeed, it's been a real joy
for us to work one-on-one

with teachers in classrooms
to help improve STEM learning

by just making these
simple changes.

It's amazing how
just small changes

in the timing of the lessons

can create more learning
in the classroom.

And indeed, this is a
free, innovative way

to improve education.

And we're actively
studying how to develop

these types of interventions

so that we can encourage
forgetting in the classroom

and encourage teachers
to think about

how they can encourage
forgetting in their students.

So this is just an
active area of research

and is, you know,
to be determined

how much more
we can do with this.

You know, in another
year or two,

please contact me and
we'll have more information

about how the curriculum
interventions are going.

Another concluding thought

that I really wanted
to share with you today

is how researchers
are actively studying

forgetting in the current times,

namely during the
COVID-19 pandemic.

And if you're like me,
you may have noticed,

particularly during
the lockdown period,

that your thinking
and learning have changed

during the pandemic
and in particular,

that you've forgotten
faster than you normally do.

So you might lose your keys.

You might not know
what you had for lunch.

You're forgetting things that
you normally wouldn't forget.

And there's a number
of reasons of why

you were experiencing
that faster forgetting.

Here's a quick summary of what
research has found.

So first, we know that
there are routine changes.

You're not going
into the office,

you're not going to the gym.

And the reason that
that affects our memory

is that our routines
serve as memory cues.

We learn where we
always put our keys

when we go to the office,
where we put our lunch,

who we talk to and have
chit-chat with in the hallway.

And when we lose that routine,
we lose the cues.

And so what that's doing is
it's speeding up forgetting.

If we don't have the cues,
we're not gonna remember,

and we're gonna
continue to forget

according to that faster rate.

The second reason
that we observe

faster forgetting
during the pandemic

has to do with a lack
of social interaction.

Social interaction is
important for so many reasons.

And I want to highlight two now.

So during the pandemic,

you haven't spent as
much time with people

and people also
serve as memory cues.

They prompt you to
talk about your past.

So just imagine that you're
chatting with a friend

or a family member,
they might say,

"So what'd you do last week?"

And you responded with,

"Well, I got to talk
to some friends.

I spent some time,
it was so much fun."

And what you're doing
by having that conversation

is you're recollecting
your past experiences

and sharing them with that
other person.

And so when people aren't
around to prompt you,

you're not engaging as much
practice in retrieving the past.

And again, that contributes
to how fast you forget.

The other reason that social
partners are so important

for our memory is
that they contribute

to our emotional well-being.

And we know from a long history
of research

on emotions and memory

is that when we're
experiencing more volatile,

emotional experiences,

and when we're sort
of experiencing

more negative life events,

that we actually forget faster
during those times.

And so for those of you
who are really missing

being with other people,
and, you know,

are just sort of having
a case of the blues,

you're forgetting faster may be

because of your
current emotional state

or the emotional state
that you experienced,

particularly during the lockdown

when you had little to no
social interaction with people.

So there are many reasons
that our social partners

are particularly important
for our memory.

The third reason that we think
people are forgetting faster

during the pandemic is that
we're engaging in more behaviors

that speed up forgetting.

And one of those behaviors
is alcohol consumption.

So there's a lot
of research showing

that during the last 18 months,

people have been
drinking more alcohol

and engaging in more drug use

than they did prior
to the pandemic.

And we know from research
on alcohol and drugs

that they act as a
memory destabilizer

and therefore cause
faster forgetting.

So if you're engaging
in an over-consumption

of these substances, that can
lead to complete memory loss.

Not only are you
forgetting faster,

but you might not have
any access to memories

from those states
of over consumption.

So certainly we think that
a lot of the forgetting

that's happening
because of the pandemic

is because people are choosing
to engage in behaviors

that are negative, that they
for memory at least,

that they didn't before.

The last reason is that many
of us during the pandemic

had lifestyle changes.

And one of the
big lifestyle changes

is that many of us
exercised less.

And this is even despite the
public service announcements

in the news encouraging people

to get out there
and go on a walk,

be outside, exercise.

And one of the reasons for that
public service announcement

or why it was in the news
all the time

is that we know that
exercise is so valuable

for so many things,

our physical health,
our mental health,

and the rate at which
we forget information.

We have a long sort of
big body of work showing

that for those of us who engage
in more cardiovascular exercise,

but exercise more generally too,

that we are more,
we're more readily able

to retrieve important
information when we need to.

So in other words,
exercise is good

and supports our ability
to retrieve information.

And so, because of that, we,

you know, are forgetting faster
if we're exercising less.

So in brief, there's a lot
of lifestyle changes

that we made that aren't for the
benefit of our memories.

And that's yet another reason

why we might be
forgetting faster.

And researchers are
actively studying,

now that we're coming
out of the pandemic,

how our forgetting is changing.

We expect that once we establish
those new routines,

live a healthier lifestyle,

that our forgetting
will slow and go back

to be what it was pre-pandemic.

But we're also concerned that
a small group of individuals

might not make those changes,

might continue to experience
negative effects of the pandemic

and thus have faster forgetting.

So researchers are actively
trying to figure out

how we can identify
those individuals

so that we can help them.

My final concluding thought
is just to say

that we don't know
why we forget,

and we are actively
studying it now,

but we do know that forgetting
is essential for our lives.

Forgetting can help us
to remember.

It can help us
to learn new things,

like new words and concepts.

But most importantly,
it can define who we are.

If we think back
to the pandemic,

there's a lot of things

that we probably want
to forget, right?

We had a lot of
negative experiences,

particularly during
the lockdown period,

and that forgetting is good.

So even though you may
have forgotten faster

during the pandemic and
forgotten a lot of the things

that happened to you,

I would argue that
that's a good thing.

What your mind and
brain are doing

is they're abstracting out
what's important to remember,

hopefully the good things
and the parts of yourself

that were able to endure
during the pandemic.

And I'm hoping for all of you,

that you have a
stronger sense of self

and know more about how you
can endure in tough situations.

And forgetting is
gonna help you do that.

It's gonna help you to
remember when you were strong.

So on that note, I just
want to say forgetting,

although intuitively may
seem like a bad thing,

is a great thing,

and it's helping you with all
facets of your life.

Thank you so much for listening.

Please feel free to reach out

if you have questions
about forgetting.

As I mentioned at the
beginning of the talk,

I spend lots of time
thinking and learning

about thinking and learning,

and I would love to do that
with you as well.

Good evening.