1
00:00:07,049 --> 00:00:09,468
[narrator] Some moments feel so important,
2
00:00:09,551 --> 00:00:12,054
we believe there is
a perfect recording of them
3
00:00:12,137 --> 00:00:13,472
etched in our minds.
4
00:00:13,555 --> 00:00:16,141
[Neil Armstrong]
That's one small step for man...
5
00:00:16,225 --> 00:00:17,768
Tear down this wall!
6
00:00:17,851 --> 00:00:18,810
[clamoring]
7
00:00:20,771 --> 00:00:22,648
Diana, Princess of Wales, is dead.
8
00:00:23,732 --> 00:00:26,735
[narrator]
For many, 9/11 was one of those moments.
9
00:00:27,945 --> 00:00:30,906
[woman 1] I was getting ready
to go to class, and I put on the TV--
10
00:00:30,989 --> 00:00:35,244
[woman 2] And the newscaster stopped
and said, "This just in."
11
00:00:35,327 --> 00:00:37,329
[man 1] Two planes hit the Twin Towers.
12
00:00:37,412 --> 00:00:40,499
[woman 3] Every single channel had
a building that was on fire.
13
00:00:40,832 --> 00:00:44,127
[man 2] This businessman was
covered in dust.
14
00:00:44,378 --> 00:00:46,421
[woman 4] And I saw the big hole
in the side of the building.
15
00:00:46,505 --> 00:00:47,881
[man 3] Yeah, it was sort of surreal.
16
00:00:47,965 --> 00:00:49,591
[woman 5] Very confusing and disorienting.
17
00:00:49,675 --> 00:00:51,009
[woman 2] I felt a sense of dread.
18
00:00:51,093 --> 00:00:55,347
[woman 6] I remember my mom was working
in the city and I remember
19
00:00:55,430 --> 00:00:59,351
smoke billowing out over the water
of the Long Island Sound
20
00:00:59,643 --> 00:01:02,271
behind the building where I went
to elementary school.
21
00:01:03,105 --> 00:01:07,234
I was just talking with my parents
about it one day and my mom goes,
22
00:01:07,317 --> 00:01:10,112
"No, you know in 2001,
23
00:01:10,237 --> 00:01:11,738
I was working in Connecticut."
24
00:01:12,155 --> 00:01:14,908
[narrator] And there were other problems
with Melanie's memory of that day.
25
00:01:15,492 --> 00:01:18,245
Her classroom windows didn't look out
over the water,
26
00:01:18,579 --> 00:01:21,123
the World Trade Center
was over 40 miles away,
27
00:01:21,623 --> 00:01:24,251
and the smoke was drifting
in the opposite direction.
28
00:01:25,252 --> 00:01:31,008
How could I possibly have seen the smoke
billowing from over the water?
29
00:01:31,091 --> 00:01:32,593
Like, how would I see that?
30
00:01:32,968 --> 00:01:37,222
[woman] Your memories for 9/11 are
probably not as accurate as you think.
31
00:01:37,306 --> 00:01:40,475
We know about 50% of the details
of that memory change in a year
32
00:01:40,559 --> 00:01:44,771
even though most people are convinced
they're a hundred percent right.
33
00:01:44,855 --> 00:01:47,357
[narrator] They might correctly remember
the gist of the day,
34
00:01:47,441 --> 00:01:49,484
but not details like
who they were with,
35
00:01:49,568 --> 00:01:52,863
what they were doing when they heard,
and what exactly they saw.
36
00:01:53,488 --> 00:01:55,907
Even our most significant memories,
37
00:01:56,033 --> 00:01:58,619
the ones that form the foundation
of our life story,
38
00:01:58,785 --> 00:02:00,287
aren't perfect recordings.
39
00:02:00,662 --> 00:02:02,914
They can shift and warp over time.
40
00:02:03,373 --> 00:02:06,710
It feels like the whole purpose of memory
should be to preserve the past.
41
00:02:06,918 --> 00:02:09,212
So why are memories so unreliable?
42
00:02:10,047 --> 00:02:13,216
How exactly does remembering work?
43
00:02:15,010 --> 00:02:18,639
Wait a second now,
I do remember, you're... Um...
44
00:02:19,806 --> 00:02:21,933
Memory, that everybody has,
45
00:02:22,059 --> 00:02:27,064
is a gold mine of unexplored
and untapped potential.
46
00:02:27,898 --> 00:02:31,318
[man 1] Our memory just mediates
our interaction with the world.
47
00:02:32,110 --> 00:02:35,405
[man 2] Memory is one of our
most fundamental activities,
48
00:02:35,489 --> 00:02:39,409
and it is only when it fails us
that we think about it at all.
49
00:02:48,168 --> 00:02:50,879
[narrator] Yanjaa Wintersoul
is a grand master of memory.
50
00:02:51,129 --> 00:02:52,798
[man] Alright, here we go.
51
00:02:52,881 --> 00:02:56,635
[narrator] Five years ago, she discovered
the world of memory competitions.
52
00:02:56,718 --> 00:02:57,803
[Wintersoul] When I first started,
53
00:02:57,886 --> 00:03:00,055
it was mostly, like,
a bunch of white guys from Europe
54
00:03:00,639 --> 00:03:04,142
in very, like, sad-looking
competition rooms.
55
00:03:04,935 --> 00:03:07,187
[narrator]
They memorize decks of cards in seconds,
56
00:03:07,270 --> 00:03:09,064
thousands of digits in an hour.
57
00:03:09,398 --> 00:03:12,693
It looks like we're all taking
very speedy SATs.
58
00:03:13,068 --> 00:03:14,820
I have three world records:
59
00:03:14,903 --> 00:03:19,074
one for images, one for names and faces,
and one for words.
60
00:03:19,157 --> 00:03:21,993
[narrator] And she's demonstrated
her skills on TV shows around the world.
61
00:03:22,953 --> 00:03:24,538
Okay, page 38.
62
00:03:25,372 --> 00:03:26,540
Starts mid-sentence.
63
00:03:26,623 --> 00:03:29,626
"Information effectively by using humor."
64
00:03:29,710 --> 00:03:30,711
[applause]
65
00:03:32,713 --> 00:03:36,508
[narrator] We gave her ten minutes
to memorize these 500 numbers, and...
66
00:03:37,467 --> 00:03:39,261
Five, three, nine...
67
00:03:39,386 --> 00:03:40,595
one, six, six...
68
00:03:40,721 --> 00:03:42,848
-nine, seven...
-...four, seven, eight...
69
00:03:42,931 --> 00:03:46,017
-...seven, six, five, eight...
-...four, seven, seven, nine...
70
00:03:46,101 --> 00:03:48,228
...one, seven... two...
71
00:03:48,311 --> 00:03:49,980
-...two, two, five...
-...nine, zero, two...
72
00:03:50,063 --> 00:03:55,193
-...six, four, eight, two...
-...one, six, one, one, two.
73
00:03:55,527 --> 00:03:56,820
[narrator] How does she do that?
74
00:03:56,903 --> 00:03:58,363
-[applause from film crew]
-Yay!
75
00:03:58,739 --> 00:04:02,075
It all comes down to the peculiar way
our brains store memories.
76
00:04:02,659 --> 00:04:06,121
And perhaps no brain has taught us more
about memory than this one.
77
00:04:06,329 --> 00:04:09,332
It belonged to a man
named Henry Molaison.
78
00:04:09,791 --> 00:04:13,295
When Henry was 27,
he had brain surgery to treat epilepsy
79
00:04:13,795 --> 00:04:16,715
and the surgeon removed this little piece
of his brain.
80
00:04:16,798 --> 00:04:21,970
The surgeon noted that the procedure
resulted in no marked behavioral changes,
81
00:04:22,095 --> 00:04:26,224
with the one exception of
a very grave recent memory loss.
82
00:04:26,850 --> 00:04:30,479
It was so severe, it prevented Henry
from navigating his own house
83
00:04:30,812 --> 00:04:32,230
and recognizing his doctors.
84
00:04:33,315 --> 00:04:35,358
But Henry still had other types of memory,
85
00:04:35,442 --> 00:04:37,444
habits that don't require
conscious thought,
86
00:04:37,527 --> 00:04:38,695
like how to ride a bike,
87
00:04:38,779 --> 00:04:40,947
so-called "implicit memories."
88
00:04:41,198 --> 00:04:44,367
He also kept some conscious,
or "explicit," memories.
89
00:04:44,576 --> 00:04:46,661
He discussed historical events
with his doctor
90
00:04:46,745 --> 00:04:48,789
in this recording from the early '90s.
91
00:04:49,164 --> 00:04:51,291
What happened in 1929?
92
00:04:52,334 --> 00:04:55,629
-The stock market crashed.
-It sure did.
93
00:04:55,712 --> 00:04:58,089
[narrator]
That's an example of semantic memory:
94
00:04:58,173 --> 00:05:02,511
facts, dates, numbers, words, the kinds
of things that memory athletes memorize.
95
00:05:03,094 --> 00:05:05,764
The real damage was
to Henry's episodic memory,
96
00:05:05,847 --> 00:05:07,974
his memory for personal experiences.
97
00:05:08,642 --> 00:05:11,520
When his doctor asked,
"Do you know what you did yesterday,"
98
00:05:11,645 --> 00:05:12,604
he replied...
99
00:05:12,687 --> 00:05:13,730
No, I don't.
100
00:05:14,815 --> 00:05:16,566
How about this morning?
101
00:05:17,692 --> 00:05:19,236
I don't even remember that.
102
00:05:20,612 --> 00:05:22,697
[narrator]
Without this one small part of his brain,
103
00:05:22,864 --> 00:05:24,741
Henry had trouble forming new memories.
104
00:05:25,534 --> 00:05:28,703
But that doesn't mean memories
are stored in one specific place.
105
00:05:29,788 --> 00:05:32,707
[cello playing]
106
00:05:32,791 --> 00:05:35,627
[narrator] When you have an experience,
say performing at a recital,
107
00:05:36,253 --> 00:05:39,798
sensory information is processed
to many different parts of your brain.
108
00:05:39,881 --> 00:05:41,341
The sound of the cello.
109
00:05:43,426 --> 00:05:45,762
The feeling of the strings
under your fingers.
110
00:05:47,681 --> 00:05:49,474
The face of your friend in the audience.
111
00:05:51,226 --> 00:05:52,769
The pang of stage fright.
112
00:05:55,146 --> 00:05:57,148
[cello continues]
113
00:06:01,027 --> 00:06:03,488
And the part of the brain that pulls
all of these elements together,
114
00:06:03,947 --> 00:06:06,449
the part that Henry's surgery
badly damaged,
115
00:06:07,450 --> 00:06:09,202
is the medial temporal lobe,
116
00:06:09,286 --> 00:06:12,747
which includes an important structure
called the hippocampus.
117
00:06:13,748 --> 00:06:15,792
When you relive that moment later,
118
00:06:15,959 --> 00:06:19,337
the medial temporal lobe
helps combine those elements once again.
119
00:06:22,632 --> 00:06:26,052
Your life story is all the moments
like this that you can relive.
120
00:06:27,137 --> 00:06:30,307
In this graph is the life story
of a typical 70-year-old.
121
00:06:31,224 --> 00:06:33,268
There are lots of memories
from the recent past,
122
00:06:33,351 --> 00:06:36,146
but as you move backward in time,
they start to fall off.
123
00:06:36,938 --> 00:06:39,149
There are only a few memories
from childhood,
124
00:06:39,524 --> 00:06:41,067
and nothing before around three,
125
00:06:41,776 --> 00:06:44,613
but there's this surprising bump
in our teens and 20s.
126
00:06:44,738 --> 00:06:47,949
When you're getting through high school,
you're having a lot of momentous occasions
127
00:06:48,033 --> 00:06:49,618
in that stage of your life.
128
00:06:49,701 --> 00:06:51,703
And when we think about our life stories,
129
00:06:51,953 --> 00:06:54,497
those change moments are the ones
that stand out
130
00:06:54,581 --> 00:06:56,583
as the ones that kind of define us
131
00:06:56,666 --> 00:06:58,460
and define our lives going forward.
132
00:06:58,543 --> 00:07:00,712
[narrator] Some people have
more memories than others,
133
00:07:01,421 --> 00:07:04,925
and you can improve your memory by just
living a healthier and more active life.
134
00:07:05,175 --> 00:07:09,554
I try to, like, not drink as much,
sleep a lot, and eat well.
135
00:07:09,638 --> 00:07:12,140
The one thing that I've seen
in every single study
136
00:07:12,307 --> 00:07:15,060
that's like "this is gonna work"
is honestly meditation.
137
00:07:15,143 --> 00:07:18,855
[narrator] Undergraduates were able
to increase their score on the verbal GREs
138
00:07:18,939 --> 00:07:23,193
from 460 to 520, just by taking
a mindfulness meditation class.
139
00:07:23,610 --> 00:07:28,073
Probably because meditation
improves focus and focus improves memory.
140
00:07:28,490 --> 00:07:30,784
And when it comes to personal experiences,
141
00:07:30,867 --> 00:07:34,037
there are certain features that make us
remember some better than others.
142
00:07:34,871 --> 00:07:36,373
First, emotion.
143
00:07:36,957 --> 00:07:39,084
If you show a person a string of faces,
144
00:07:39,167 --> 00:07:41,419
they'll remember
the most emotional ones best.
145
00:07:41,753 --> 00:07:44,714
When we have an emotional experience,
our amygdala,
146
00:07:44,798 --> 00:07:49,052
the emotional center of the brain,
which sits right next to the hippocampus,
147
00:07:49,386 --> 00:07:51,638
actually up-regulates the hippocampus
148
00:07:51,972 --> 00:07:56,726
and allows it to form
a more detailed and stronger memory.
149
00:07:56,810 --> 00:07:58,728
One of the things we wanted to do
after 9/11
150
00:07:58,812 --> 00:08:03,191
was look into the brains of individuals
who were in New York that day.
151
00:08:03,274 --> 00:08:07,278
So about half the people were,
on average, around Midtown,
152
00:08:07,404 --> 00:08:10,782
and the other half of people were
much closer to the World Trade Center.
153
00:08:11,700 --> 00:08:13,118
[narrator] Three years after the attacks,
154
00:08:13,201 --> 00:08:15,620
they asked those people to remember
their experiences.
155
00:08:15,996 --> 00:08:19,749
[Addis] The individuals who were closer
to the World Trade Center that day,
156
00:08:19,833 --> 00:08:24,754
the 9/11 memories were more vivid
and we saw more activity in the amygdala.
157
00:08:26,131 --> 00:08:28,508
[narrator] Memories are also connected
to a sense of place.
158
00:08:29,426 --> 00:08:32,429
One of the things we know from our study
of 9/11 memories is that
159
00:08:32,512 --> 00:08:35,390
the thing that people were
most consistent about was where they were.
160
00:08:35,890 --> 00:08:38,393
-[man 1] I had just gotten home.
-[man 2] Gym class.
161
00:08:38,476 --> 00:08:40,186
[man 3] I was living in London
at the time.
162
00:08:40,270 --> 00:08:41,938
[woman] In New Smyrna Beach, Florida.
163
00:08:42,022 --> 00:08:43,481
[man 4] The Upper East Side.
164
00:08:43,565 --> 00:08:46,860
So we think place
has a particularly strong role in memory.
165
00:08:47,318 --> 00:08:49,154
And if you actually look
in the hippocampus,
166
00:08:49,237 --> 00:08:52,615
there seem to be cells that are
specifically responsive to time and place.
167
00:08:53,033 --> 00:08:54,951
[narrator] Here's a representation
of these "place" cells
168
00:08:55,035 --> 00:08:57,287
in the hippocampus of one particular rat.
169
00:08:57,954 --> 00:09:00,915
And here's a video of that rat
moving along a simple track.
170
00:09:00,999 --> 00:09:03,626
His head is in this green circle,
and here's his tail.
171
00:09:04,919 --> 00:09:08,757
Each place cell is associated with
a particular location along the track
172
00:09:08,840 --> 00:09:11,468
and these cells have been color-coded
by scientists.
173
00:09:11,551 --> 00:09:15,346
When the rat is at the start of the maze,
this green place cell fires.
174
00:09:15,430 --> 00:09:18,266
But as it moves along,
a different cell is activated,
175
00:09:18,349 --> 00:09:20,351
and then another, and another.
176
00:09:20,643 --> 00:09:24,898
When the rat pauses, the cells fire in
rapid succession as he recalls his route.
177
00:09:26,983 --> 00:09:29,611
London cabbies must navigate
their own rat maze.
178
00:09:30,111 --> 00:09:33,948
To get their licenses, they have to pass
a century-old test called simply
179
00:09:34,365 --> 00:09:35,658
"the knowledge."
180
00:09:35,742 --> 00:09:39,788
They spend years memorizing
London's 25,000 streets.
181
00:09:39,871 --> 00:09:42,707
Scientists scanned the brains
of would-be cabbies
182
00:09:42,791 --> 00:09:44,584
before and after this process.
183
00:09:44,959 --> 00:09:47,670
In the brains of people
who didn't end up getting their licenses,
184
00:09:47,796 --> 00:09:50,256
the size of the hippocampus
didn't really change.
185
00:09:50,423 --> 00:09:54,719
But those who passed, interestingly,
their hippocampi actually grew.
186
00:09:55,887 --> 00:09:56,721
[cello plays]
187
00:09:57,222 --> 00:10:00,183
Finally, memories can be strengthened
by story.
188
00:10:01,226 --> 00:10:03,853
Our brains pay much closer attention
to information
189
00:10:03,937 --> 00:10:05,772
when it's in the form of a narrative.
190
00:10:07,148 --> 00:10:11,569
In one study, 24 people were asked
to memorize 12 lists of ten words.
191
00:10:12,153 --> 00:10:14,364
Half the people
studied and rehearsed the list,
192
00:10:14,447 --> 00:10:17,867
and they remembered, on average,
13% of the words.
193
00:10:18,243 --> 00:10:22,247
The other half wove the words
into stories of their own invention,
194
00:10:22,372 --> 00:10:25,125
and they remembered 93%.
195
00:10:25,208 --> 00:10:29,087
The more that you can associate
things you want to remember
196
00:10:29,337 --> 00:10:31,840
with structures you already have
in your mind,
197
00:10:31,965 --> 00:10:33,508
the easier it's going to be to remember.
198
00:10:33,591 --> 00:10:35,426
You know, you're creating a narrative.
199
00:10:35,510 --> 00:10:37,720
When we go to retrieve that memory,
200
00:10:37,804 --> 00:10:41,683
we have almost many multiple ways
of getting into that memory.
201
00:10:42,392 --> 00:10:44,811
[narrator] Story, place, and emotion
are the foundation
202
00:10:44,894 --> 00:10:46,771
of some of our strongest memories.
203
00:10:47,021 --> 00:10:50,024
And those same features can be hijacked
to help you, say,
204
00:10:50,108 --> 00:10:52,652
memorize 500 random digits.
205
00:10:52,735 --> 00:10:53,987
Yes, let's do it.
206
00:10:54,362 --> 00:10:56,239
[narrator]
Starting with the first three digits,
207
00:10:56,322 --> 00:10:59,701
she converts numbers into sounds
using her own personal code.
208
00:11:00,118 --> 00:11:02,036
[Wintersoul] So 5 is an "s,"
209
00:11:02,245 --> 00:11:07,584
3 is an "a," and 9 is a "g," 'cause--
just because of the shapes.
210
00:11:07,667 --> 00:11:09,836
So then it's basically like
you're reading something
211
00:11:09,919 --> 00:11:11,963
instead of looking at all these numbers.
212
00:11:12,046 --> 00:11:14,716
So 539 is SAG.
213
00:11:15,091 --> 00:11:18,261
[narrator] And the next triplet, 166,
becomes TBB.
214
00:11:18,595 --> 00:11:21,973
[Wintersoul] And I think of
the Middle Eastern dish of tabbouleh.
215
00:11:22,056 --> 00:11:25,643
[narrator] She pairs the two words
to create a striking scenario.
216
00:11:25,727 --> 00:11:29,981
[Wintersoul] This saggy, half-naked person
is covered in, like, tabbouleh rice,
217
00:11:30,064 --> 00:11:32,567
and because it's disgusting,
I remember it more.
218
00:11:32,650 --> 00:11:35,445
Anything that has, like, visceral
or, like, very emotional things,
219
00:11:35,528 --> 00:11:36,654
your brain is like, ugh.
220
00:11:36,738 --> 00:11:39,032
[narrator] She translates
the rest of the digits the same way.
221
00:11:39,115 --> 00:11:42,619
[Wintersoul] Gimli from Lord of the Rings,
he is running for office.
222
00:11:43,119 --> 00:11:45,496
Rami Malek buying boots.
223
00:11:45,622 --> 00:11:47,624
My spleen turns into the Lourve.
224
00:11:48,124 --> 00:11:50,585
[narrator]
Next, Yanjaa harnesses the power of place
225
00:11:50,668 --> 00:11:53,880
with an ancient technique called
"the memory palace."
226
00:11:54,464 --> 00:11:57,675
She imagines herself walking through
a neighborhood she knows well,
227
00:11:57,759 --> 00:11:59,761
adding surreal imagery along the route.
228
00:11:59,844 --> 00:12:01,512
It helps in putting...
229
00:12:02,013 --> 00:12:04,724
very random abstract things in order
230
00:12:04,807 --> 00:12:06,559
when you attach it to something
you already know.
231
00:12:06,643 --> 00:12:09,187
So I come out of the High Street metro.
232
00:12:09,437 --> 00:12:12,273
So a saggy-skinned person
233
00:12:12,690 --> 00:12:14,484
is just covered in tabbouleh.
234
00:12:14,943 --> 00:12:16,736
[narrator] And a little further on...
235
00:12:16,819 --> 00:12:20,240
[Wintersoul]
In that tunnel, 478, that's a reef,
236
00:12:20,323 --> 00:12:22,325
and 468, that's ravioli,
237
00:12:22,408 --> 00:12:26,788
so it's a tunnel that's now a reef
and full of ravioli.
238
00:12:26,871 --> 00:12:31,251
On the carousel,
we'll have a big alpaca llama
239
00:12:31,459 --> 00:12:35,546
and it's, like, eating this tube
of, like, melted cheese.
240
00:12:35,838 --> 00:12:39,384
That dull list of numbers
became an epic travel log
241
00:12:39,467 --> 00:12:42,178
full of surprising images
that she could revisit later.
242
00:12:42,595 --> 00:12:45,974
Memory athletes aren't necessarily
smarter than everyday people
243
00:12:46,057 --> 00:12:47,767
and they don't have bigger brains.
244
00:12:47,850 --> 00:12:50,311
But they change the connections
within their brains
245
00:12:50,395 --> 00:12:52,814
by training with techniques
like the memory palace.
246
00:12:53,022 --> 00:12:54,274
We are more...
247
00:12:55,024 --> 00:12:58,361
wired to remember that
than to remember random sets of digits.
248
00:12:58,778 --> 00:13:01,698
In general, we're like emotional
and visual learners.
249
00:13:02,073 --> 00:13:03,533
And storytellers.
250
00:13:04,575 --> 00:13:09,414
Only a dozen people in the world have
memorized more than 20,000 digits of Pi.
251
00:13:10,373 --> 00:13:12,834
But lots and lots of people
have played Hamlet
252
00:13:12,917 --> 00:13:14,752
and memorized all his lines...
253
00:13:14,836 --> 00:13:16,504
Words, words, words.
254
00:13:16,587 --> 00:13:19,132
...which contain nearly 50,000 letters.
255
00:13:19,257 --> 00:13:20,925
Remember thee!
256
00:13:21,926 --> 00:13:26,931
Ay, thou poor ghost, while memory
holds a seat in this distracted globe.
257
00:13:27,015 --> 00:13:28,558
[narrator]
But that's not the full story.
258
00:13:29,517 --> 00:13:32,186
Some of the same things
that strengthen our memories
259
00:13:32,437 --> 00:13:33,688
can also warp them.
260
00:13:34,105 --> 00:13:35,898
And typically with emotional memories,
261
00:13:35,982 --> 00:13:38,651
we tend to remember the central aspects.
262
00:13:38,776 --> 00:13:43,489
So, our attention kind of zooms in
on the core of that experience,
263
00:13:43,573 --> 00:13:46,117
so we might forget
some of the peripheral details,
264
00:13:46,367 --> 00:13:50,621
like, you know, perhaps what a perpetrator
was wearing, but we'll remember the gun.
265
00:13:50,705 --> 00:13:55,209
Emotional 9/11 memories are
just as inaccurate as everyday memories.
266
00:13:55,418 --> 00:13:57,587
They both deteriorate at the same rate.
267
00:13:58,046 --> 00:14:01,215
[Phelps] What was different is that
people were highly confident
268
00:14:01,299 --> 00:14:03,176
their memories for 9/11 were correct.
269
00:14:03,259 --> 00:14:04,093
[record needle scratches]
270
00:14:04,594 --> 00:14:07,597
Memories aren't high fidelity recordings
that we store away.
271
00:14:08,389 --> 00:14:10,892
They're more like live performances,
272
00:14:11,017 --> 00:14:15,063
created with input from different parts
of the brain in the present moment.
273
00:14:15,855 --> 00:14:19,692
We can't remember every single detail
of every experience.
274
00:14:20,068 --> 00:14:22,570
And so we use pre-existing knowledge,
275
00:14:22,653 --> 00:14:26,032
such as semantic memory
or facts that we have...
276
00:14:26,157 --> 00:14:28,534
[narrator]
Or our pre-existing biases and beliefs.
277
00:14:28,701 --> 00:14:30,578
[Addis] ...to fill in those gaps.
278
00:14:30,953 --> 00:14:34,499
That could explain the errors
in Melanie's memory of 9/11.
279
00:14:34,874 --> 00:14:37,543
My mom worked in New York City
growing up all my life,
280
00:14:37,627 --> 00:14:39,337
so, of course she was in the city.
281
00:14:39,420 --> 00:14:43,549
[narrator] And after 9/11, maybe Melanie
saw billowing smoke on TV,
282
00:14:43,633 --> 00:14:45,510
and that's how it entered her memory.
283
00:14:45,593 --> 00:14:48,763
So the fact that we reconstruct
our episodic memory
284
00:14:48,846 --> 00:14:50,973
so we piece them back together
285
00:14:51,099 --> 00:14:54,769
means that our episodic memories
are actually very flexible.
286
00:14:54,852 --> 00:14:57,814
[narrator] Scientists have been able
to exploit this flexibility
287
00:14:57,897 --> 00:15:00,983
to plant false childhood memories
of being left at a shopping mall,
288
00:15:01,943 --> 00:15:03,319
taking a hot air balloon ride,
289
00:15:03,736 --> 00:15:05,947
even having tea with Prince Charles.
290
00:15:06,406 --> 00:15:09,283
In one study, young adults
were asked to try to remember
291
00:15:09,367 --> 00:15:11,828
a crime they had supposedly committed
in their teens,
292
00:15:12,078 --> 00:15:14,414
even though these crimes
were completely fake,
293
00:15:14,622 --> 00:15:15,915
made up by researchers.
294
00:15:15,998 --> 00:15:18,626
After a couple of interviews
full of leading questions,
295
00:15:19,043 --> 00:15:22,880
70% of the subjects accepted
that they had committed those crimes
296
00:15:22,964 --> 00:15:25,633
and many came up with
rich, detailed memories
297
00:15:25,716 --> 00:15:27,468
-that were completely false.
-[siren wails]
298
00:15:27,969 --> 00:15:29,595
One of the places where this plays out
299
00:15:29,679 --> 00:15:33,015
that is unfortunate is things like,
um, eyewitness identifications.
300
00:15:33,099 --> 00:15:36,018
They said they were gonna take you
into a room, we're gonna have seven men,
301
00:15:36,144 --> 00:15:38,521
and that if I saw the suspect,
302
00:15:38,604 --> 00:15:40,940
I was to write his number
on a piece of paper
303
00:15:41,023 --> 00:15:42,733
and hand it over to the detective.
304
00:15:42,817 --> 00:15:45,194
[narrator] More than two decades
after she was raped,
305
00:15:45,486 --> 00:15:48,656
Jennifer Thompson appeared on television
with the man she had identified
306
00:15:48,739 --> 00:15:49,907
as her attacker.
307
00:15:49,991 --> 00:15:52,201
After I picked out
Ronald Cotton's photograph,
308
00:15:52,535 --> 00:15:54,912
that's when they said to me,
"We thought that was him."
309
00:15:54,996 --> 00:15:57,665
We can boost the confidence
in a false memory
310
00:15:57,748 --> 00:16:01,085
by confirming it or by
at least repeating it multiple times.
311
00:16:01,169 --> 00:16:05,965
By now, Ronald's image had
completely contaminated, so to speak,
312
00:16:06,215 --> 00:16:08,551
the original memory of that night,
and so...
313
00:16:09,010 --> 00:16:11,554
the face of my rapist
had become Ronald Cotton,
314
00:16:11,929 --> 00:16:16,142
so much so that seeing
the actual perpetrator right there...
315
00:16:17,768 --> 00:16:19,729
I didn't have one memory of it.
316
00:16:19,812 --> 00:16:21,898
Years after Ronald was imprisoned,
317
00:16:21,981 --> 00:16:25,651
DNA evidence proved that Jennifer
had been raped by another man.
318
00:16:25,735 --> 00:16:29,864
In the U.S., DNA has helped to overturn
hundreds of convictions,
319
00:16:29,947 --> 00:16:33,034
and 70% of those involved
eyewitness testimony.
320
00:16:34,869 --> 00:16:38,623
It's not just our memories of crimes
that can become contaminated.
321
00:16:38,706 --> 00:16:42,543
It's the memories that tell us who we are
and where we came from.
322
00:16:42,960 --> 00:16:45,213
Researchers interviewed
a group of 14-year-olds,
323
00:16:45,296 --> 00:16:49,050
and then, decades later, asked them
to recall their teenage years.
324
00:16:49,133 --> 00:16:51,344
What their relationship with their parents
was like,
325
00:16:51,427 --> 00:16:53,346
how they had felt about sex
and religion,
326
00:16:53,429 --> 00:16:55,097
what activities they had enjoyed.
327
00:16:55,264 --> 00:16:58,309
Their memories, it turned out,
were uniformly poor.
328
00:16:58,434 --> 00:17:01,229
For most memories, no better than chance.
329
00:17:01,687 --> 00:17:05,024
So this poses the question:
Why would we have a memory system
330
00:17:05,149 --> 00:17:11,364
that is so unreliable and error-prone
if it was designed to remember the past?
331
00:17:11,697 --> 00:17:12,949
[narrator] That's the big question.
332
00:17:13,407 --> 00:17:16,494
And once again, those recordings
of Henry Molaison
333
00:17:16,577 --> 00:17:18,162
point to a possible answer.
334
00:17:18,538 --> 00:17:20,373
What do you think you'll do tomorrow?
335
00:17:21,290 --> 00:17:22,875
Whatever is beneficial.
336
00:17:23,668 --> 00:17:26,128
[narrator] Henry often struggled
to answer questions like this.
337
00:17:26,379 --> 00:17:29,090
It seemed to scientists
that he hadn't just lost his past,
338
00:17:29,507 --> 00:17:31,300
he could no longer imagine the future.
339
00:17:32,885 --> 00:17:34,762
Three decades after Henry's surgery,
340
00:17:35,221 --> 00:17:38,057
another patient's medial temporal lobe
was severely damaged
341
00:17:38,140 --> 00:17:39,392
in a motorcycle accident.
342
00:17:39,475 --> 00:17:42,979
In this interview from 1988,
the patient was asked by his doctor...
343
00:17:43,062 --> 00:17:45,439
[interviewer]
Do you feel hopeful about the future?
344
00:17:50,152 --> 00:17:52,488
I guess so. I don't really think much
about the future.
345
00:17:52,572 --> 00:17:54,365
[interviewer]
You don't think much about the future?
346
00:17:55,616 --> 00:17:58,369
[narrator] That same patient
once described thinking about the future
347
00:17:58,452 --> 00:18:01,622
as being asked to find a chair
in an empty room.
348
00:18:02,498 --> 00:18:06,002
The future and the past seem to be
somehow linked in the mind.
349
00:18:06,627 --> 00:18:09,547
[Addis]
We decided to put people into the scanner
350
00:18:09,630 --> 00:18:12,174
and have them remember past experiences
351
00:18:12,258 --> 00:18:14,010
and imagine future experiences.
352
00:18:14,093 --> 00:18:15,052
And...
353
00:18:15,553 --> 00:18:17,597
we really didn't know what to expect.
354
00:18:17,680 --> 00:18:21,934
When people remembered,
a particular network lit up, and...
355
00:18:22,143 --> 00:18:26,564
[Addis] That same network was engaged,
pretty much identically
356
00:18:26,647 --> 00:18:30,026
when people were having to imagine
future events.
357
00:18:30,484 --> 00:18:33,863
[narrator] When you let your mind wander,
you switch back and forth all the time,
358
00:18:33,988 --> 00:18:35,573
remembering and imagining.
359
00:18:36,115 --> 00:18:38,451
Your mind is a time machine.
360
00:18:40,494 --> 00:18:42,496
In Lewis Carroll's
Through the Looking-Glass,
361
00:18:42,580 --> 00:18:43,956
the Queen of Hearts remarks,
362
00:18:44,040 --> 00:18:46,542
"It's a poor sort of memory
that only works backwards."
363
00:18:47,126 --> 00:18:48,878
It turns out... she's right.
364
00:18:50,338 --> 00:18:55,092
The same machinery that brings all those
pieces together to relive the past
365
00:18:55,217 --> 00:18:57,803
can bring some of those pieces together
with other pieces
366
00:18:57,887 --> 00:19:00,640
to simulate possible futures.
367
00:19:00,723 --> 00:19:04,852
Now, the flexibility that leads us
to remember things that never happened,
368
00:19:05,144 --> 00:19:07,521
that undermines the justice system,
369
00:19:07,605 --> 00:19:09,899
that corrupts our most vivid memories,
370
00:19:09,982 --> 00:19:12,068
it starts to look like a superpower,
371
00:19:12,401 --> 00:19:15,071
the key to our success as a species.
372
00:19:15,321 --> 00:19:18,616
It allows us to troubleshoot
upcoming experiences,
373
00:19:18,699 --> 00:19:21,702
to think through the ways in which
events might unfold,
374
00:19:21,786 --> 00:19:23,746
potential obstacles that might come up
375
00:19:23,829 --> 00:19:26,248
and the ways in which
we might deal with those obstacles.
376
00:19:26,832 --> 00:19:30,378
[narrator] And some scientists say
the simulation engine between your ears
377
00:19:30,461 --> 00:19:32,463
does something even more profound:
378
00:19:32,755 --> 00:19:36,634
It weaves together memories of the past
and dreams of the future
379
00:19:36,717 --> 00:19:38,594
to create your sense of self.