TEDGlobal 2013
Elizabeth Loftus: How reliable is your memory?
Filmed:
Readability: 4.7
4,637,270 views
Psychologist Elizabeth Loftus studies memories. More precisely, she studies false memories, when people either remember things that didn't happen or remember them differently from the way they really were. It's more common than you might think, and Loftus shares some startling stories and statistics -- and raises some important ethical questions.
Elizabeth Loftus - False memories scholar
Memory-manipulation expert Elizabeth Loftus explains how our memories might not be what they seem -- and how implanted memories can have real-life repercussions. Full bio
Memory-manipulation expert Elizabeth Loftus explains how our memories might not be what they seem -- and how implanted memories can have real-life repercussions. Full bio
Double-click the English transcript below to play the video.
00:12
I'd like to tell you about a legal case that I worked on
0
509
4332
00:16
involving a man named Steve Titus.
1
4841
3563
00:20
Titus was a restaurant manager.
2
8404
3029
00:23
He was 31 years old, he lived in Seattle, Washington,
3
11433
4090
00:27
he was engaged to Gretchen,
4
15523
1895
00:29
about to be married, she was the love of his life.
5
17418
2948
00:32
And one night, the couple went out
6
20366
2284
00:34
for a romantic restaurant meal.
7
22650
3005
00:37
They were on their way home,
8
25655
1648
00:39
and they were pulled over by a police officer.
9
27303
2950
00:42
You see, Titus' car sort of resembled
10
30253
3317
00:45
a car that was driven earlier in the evening
11
33570
3887
00:49
by a man who raped a female hitchhiker,
12
37457
3406
00:52
and Titus kind of resembled that rapist.
13
40863
3594
00:56
So the police took a picture of Titus,
14
44457
2578
00:59
they put it in a photo lineup,
15
47035
2767
01:01
they later showed it to the victim,
16
49802
2160
01:03
and she pointed to Titus' photo.
17
51962
2160
01:06
She said, "That one's the closest."
18
54122
3621
01:09
The police and the prosecution proceeded with a trial,
19
57743
3888
01:13
and when Steve Titus was put on trial for rape,
20
61631
3341
01:16
the rape victim got on the stand
21
64972
2096
01:19
and said, "I'm absolutely positive that's the man."
22
67068
4342
01:23
And Titus was convicted.
23
71410
2926
01:26
He proclaimed his innocence,
24
74336
1974
01:28
his family screamed at the jury,
25
76310
2582
01:30
his fiancée collapsed on the floor sobbing,
26
78892
2871
01:33
and Titus is taken away to jail.
27
81763
3395
01:37
So what would you do at this point?
28
85158
3458
01:40
What would you do?
29
88616
1636
01:42
Well, Titus lost complete faith in the legal system,
30
90252
3768
01:46
and yet he got an idea.
31
94020
2032
01:48
He called up the local newspaper,
32
96052
2431
01:50
he got the interest of an investigative journalist,
33
98483
3387
01:53
and that journalist actually found the real rapist,
34
101870
4736
01:58
a man who ultimately confessed to this rape,
35
106606
3353
02:01
a man who was thought to have committed 50 rapes
36
109959
3292
02:05
in that area,
37
113251
1332
02:06
and when this information was given to the judge,
38
114583
3174
02:09
the judge set Titus free.
39
117757
2936
02:12
And really, that's where this case should have ended.
40
120693
4031
02:16
It should have been over.
41
124724
1123
02:17
Titus should have thought of this as a horrible year,
42
125847
2520
02:20
a year of accusation and trial, but over.
43
128367
3836
02:24
It didn't end that way.
44
132203
2047
02:26
Titus was so bitter.
45
134250
2678
02:28
He'd lost his job. He couldn't get it back.
46
136928
2580
02:31
He lost his fiancée.
47
139508
1843
02:33
She couldn't put up with his persistent anger.
48
141351
2906
02:36
He lost his entire savings,
49
144257
2146
02:38
and so he decided to file a lawsuit
50
146403
2858
02:41
against the police and others whom he felt
51
149261
2281
02:43
were responsible for his suffering.
52
151542
2319
02:45
And that's when I really started working on this case,
53
153861
4713
02:50
trying to figure out
54
158574
1961
02:52
how did that victim go from
55
160535
2074
02:54
"That one's the closest"
56
162609
1528
02:56
to "I'm absolutely positive that's the guy."
57
164137
4750
03:00
Well, Titus was consumed with his civil case.
58
168887
3279
03:04
He spent every waking moment thinking about it,
59
172166
3034
03:07
and just days before he was to have his day in court,
60
175200
4151
03:11
he woke up in the morning,
61
179351
2219
03:13
doubled over in pain,
62
181570
1808
03:15
and died of a stress-related heart attack.
63
183378
2694
03:18
He was 35 years old.
64
186072
3187
03:21
So I was asked to work on Titus' case
65
189259
4810
03:26
because I'm a psychological scientist.
66
194069
2515
03:28
I study memory. I've studied memory for decades.
67
196584
3827
03:32
And if I meet somebody on an airplane --
68
200411
3389
03:35
this happened on the way over to Scotland --
69
203800
2096
03:37
if I meet somebody on an airplane,
70
205896
1830
03:39
and we ask each other, "What do you do? What do you do?"
71
207726
3045
03:42
and I say "I study memory,"
72
210771
1451
03:44
they usually want to tell me how they have trouble remembering names,
73
212222
3380
03:47
or they've got a relative who's got Alzheimer's
74
215602
2799
03:50
or some kind of memory problem,
75
218416
2065
03:52
but I have to tell them
76
220481
2216
03:54
I don't study when people forget.
77
222697
3505
03:58
I study the opposite: when they remember,
78
226202
3002
04:01
when they remember things that didn't happen
79
229204
2753
04:03
or remember things that were different
80
231957
1965
04:05
from the way they really were.
81
233922
2025
04:07
I study false memories.
82
235947
4736
04:12
Unhappily, Steve Titus is not the only person
83
240683
4307
04:16
to be convicted based on somebody's false memory.
84
244990
4305
04:21
In one project in the United States,
85
249295
3308
04:24
information has been gathered
86
252603
2252
04:26
on 300 innocent people,
87
254855
3934
04:30
300 defendants who were convicted of crimes they didn't do.
88
258789
3895
04:34
They spent 10, 20, 30 years in prison for these crimes,
89
262684
5300
04:39
and now DNA testing has proven
90
267984
2427
04:42
that they are actually innocent.
91
270411
2916
04:45
And when those cases have been analyzed,
92
273327
2521
04:47
three quarters of them
93
275848
2141
04:49
are due to faulty memory, faulty eyewitness memory.
94
277989
5611
04:55
Well, why?
95
283600
1263
04:56
Like the jurors who convicted those innocent people
96
284863
3451
05:00
and the jurors who convicted Titus,
97
288314
2284
05:02
many people believe that memory
98
290598
2241
05:04
works like a recording device.
99
292839
1647
05:06
You just record the information,
100
294486
2257
05:08
then you call it up and play it back
101
296743
2647
05:11
when you want to answer questions or identify images.
102
299390
3427
05:14
But decades of work in psychology
103
302817
2163
05:16
has shown that this just isn't true.
104
304980
3153
05:20
Our memories are constructive.
105
308133
2430
05:22
They're reconstructive.
106
310563
1569
05:24
Memory works a little bit more like a Wikipedia page:
107
312132
3481
05:27
You can go in there and change it, but so can other people.
108
315613
5113
05:32
I first started studying this constructive memory process
109
320726
5249
05:37
in the 1970s.
110
325975
2415
05:40
I did my experiments that involved showing people
111
328390
4423
05:44
simulated crimes and accidents
112
332813
2505
05:47
and asking them questions about what they remember.
113
335318
3518
05:50
In one study, we showed people a simulated accident
114
338836
3939
05:54
and we asked people,
115
342775
1278
05:56
how fast were the cars going when they hit each other?
116
344053
2864
05:58
And we asked other people,
117
346917
1634
06:00
how fast were the cars going when they smashed into each other?
118
348551
3689
06:04
And if we asked the leading "smashed" question,
119
352240
3002
06:07
the witnesses told us the cars were going faster,
120
355242
3285
06:10
and moreover, that leading "smashed" question
121
358527
3997
06:14
caused people to be more likely to tell us
122
362524
2860
06:17
that they saw broken glass in the accident scene
123
365384
3067
06:20
when there wasn't any broken glass at all.
124
368451
3779
06:24
In another study, we showed a simulated accident
125
372230
2889
06:27
where a car went through an intersection with a stop sign,
126
375119
3660
06:30
and if we asked a question that insinuated it was a yield sign,
127
378779
4932
06:35
many witnesses told us they remember seeing a yield sign
128
383711
3849
06:39
at the intersection, not a stop sign.
129
387560
3457
06:43
And you might be thinking, well, you know,
130
391017
2189
06:45
these are filmed events,
131
393206
1323
06:46
they are not particularly stressful.
132
394529
1928
06:48
Would the same kind of mistakes be made
133
396457
2734
06:51
with a really stressful event?
134
399191
2951
06:54
In a study we published just a few months ago,
135
402142
3091
06:57
we have an answer to this question,
136
405233
2304
06:59
because what was unusual about this study
137
407537
2764
07:02
is we arranged for people to have a very stressful experience.
138
410301
5632
07:07
The subjects in this study
139
415933
2229
07:10
were members of the U.S. military
140
418162
2510
07:12
who were undergoing a harrowing training exercise
141
420672
4425
07:17
to teach them what it's going to be like for them
142
425097
2782
07:19
if they are ever captured as prisoners of war.
143
427879
3918
07:23
And as part of this training exercise,
144
431797
2430
07:26
these soldiers are interrogated in an aggressive,
145
434227
3529
07:29
hostile, physically abusive fashion for 30 minutes
146
437756
5086
07:34
and later on they have to try to identify
147
442842
2817
07:37
the person who conducted that interrogation.
148
445659
3023
07:40
And when we feed them suggestive information
149
448682
3823
07:44
that insinuates it's a different person,
150
452505
2778
07:47
many of them misidentify their interrogator,
151
455283
4037
07:51
often identifying someone who doesn't even remotely
152
459320
3835
07:55
resemble the real interrogator.
153
463155
3104
07:58
And so what these studies are showing
154
466259
2301
08:00
is that when you feed people misinformation
155
468560
3860
08:04
about some experience that they may have had,
156
472420
3380
08:07
you can distort or contaminate or change their memory.
157
475800
5655
08:13
Well out there in the real world,
158
481455
2200
08:15
misinformation is everywhere.
159
483655
2891
08:18
We get misinformation
160
486546
1360
08:19
not only if we're questioned in a leading way,
161
487906
2916
08:22
but if we talk to other witnesses
162
490822
2447
08:25
who might consciously or inadvertently feed us
163
493269
3033
08:28
some erroneous information,
164
496302
2137
08:30
or if we see media coverage about some event we might have experienced,
165
498439
4730
08:35
all of these provide the opportunity
166
503169
2793
08:37
for this kind of contamination of our memory.
167
505962
4350
08:42
In the 1990s, we began to see
168
510312
3788
08:46
an even more extreme kind of memory problem.
169
514100
4683
08:50
Some patients were going into therapy with one problem --
170
518783
3096
08:53
maybe they had depression, an eating disorder --
171
521879
2914
08:56
and they were coming out of therapy
172
524793
2753
08:59
with a different problem.
173
527546
2661
09:02
Extreme memories for horrific brutalizations,
174
530207
3701
09:05
sometimes in satanic rituals,
175
533908
1983
09:07
sometimes involving really bizarre and unusual elements.
176
535891
4697
09:12
One woman came out of psychotherapy
177
540588
2554
09:15
believing that she'd endured years
178
543142
2428
09:17
of ritualistic abuse, where she was forced into a pregnancy
179
545570
3902
09:21
and that the baby was cut from her belly.
180
549472
2566
09:24
But there were no physical scars
181
552038
2359
09:26
or any kind of physical evidence
182
554397
2026
09:28
that could have supported her story.
183
556423
2881
09:31
And when I began looking into these cases,
184
559304
3008
09:34
I was wondering,
185
562312
1450
09:35
where do these bizarre memories come from?
186
563762
2328
09:38
And what I found is that most of these situations
187
566090
4387
09:42
involved some particular form of psychotherapy.
188
570477
5491
09:47
And so I asked,
189
575968
1599
09:49
were some of the things going on in this psychotherapy --
190
577567
3388
09:52
like the imagination exercises
191
580955
2884
09:55
or dream interpretation,
192
583839
2057
09:57
or in some cases hypnosis,
193
585896
2132
10:00
or in some cases exposure to false information --
194
588028
3818
10:03
were these leading these patients
195
591846
2787
10:06
to develop these very bizarre,
196
594633
2677
10:09
unlikely memories?
197
597310
2931
10:12
And I designed some experiments
198
600241
2159
10:14
to try to study the processes that were being used
199
602400
5025
10:19
in this psychotherapy so I could study
200
607425
3073
10:22
the development of these very rich false memories.
201
610498
3551
10:26
In one of the first studies we did,
202
614049
2408
10:28
we used suggestion,
203
616457
2353
10:30
a method inspired by the psychotherapy we saw in these cases,
204
618810
4063
10:34
we used this kind of suggestion
205
622873
2110
10:36
and planted a false memory
206
624983
1852
10:38
that when you were a kid, five or six years old,
207
626835
3077
10:41
you were lost in a shopping mall.
208
629912
2251
10:44
You were frightened. You were crying.
209
632163
2500
10:46
You were ultimately rescued by an elderly person
210
634663
2514
10:49
and reunited with the family.
211
637177
1852
10:51
And we succeeded in planting this memory
212
639029
2608
10:53
in the minds of about a quarter of our subjects.
213
641637
4106
10:57
And you might be thinking, well,
214
645743
2005
10:59
that's not particularly stressful.
215
647748
2346
11:02
But we and other investigators have planted
216
650094
3369
11:05
rich false memories of things that were
217
653463
2758
11:08
much more unusual and much more stressful.
218
656221
2915
11:11
So in a study done in Tennessee,
219
659136
2539
11:13
researchers planted the false memory
220
661675
2416
11:16
that when you were a kid, you nearly drowned
221
664091
2574
11:18
and had to be rescued by a life guard.
222
666665
2507
11:21
And in a study done in Canada,
223
669172
2303
11:23
researchers planted the false memory
224
671475
2524
11:25
that when you were a kid,
225
673999
1228
11:27
something as awful as being attacked by a vicious animal
226
675227
3730
11:30
happened to you,
227
678957
1382
11:32
succeeding with about half of their subjects.
228
680339
3422
11:35
And in a study done in Italy,
229
683761
2352
11:38
researchers planted the false memory,
230
686113
2658
11:40
when you were a kid, you witnessed demonic possession.
231
688771
5212
11:45
I do want to add that it might seem
232
693983
2207
11:48
like we are traumatizing these experimental subjects
233
696190
3739
11:51
in the name of science,
234
699929
1600
11:53
but our studies have gone through thorough evaluation
235
701529
4638
11:58
by research ethics boards
236
706167
1975
12:00
that have made the decision
237
708142
2342
12:02
that the temporary discomfort that some
238
710484
3073
12:05
of these subjects might experience in these studies
239
713557
3084
12:08
is outweighed by the importance of this problem
240
716641
3900
12:12
for understanding memory processes
241
720541
3107
12:15
and the abuse of memory that is going on
242
723648
3346
12:18
in some places in the world.
243
726994
3293
12:22
Well, to my surprise,
244
730287
3038
12:25
when I published this work and began to speak out
245
733325
3429
12:28
against this particular brand of psychotherapy,
246
736754
3895
12:32
it created some pretty bad problems for me:
247
740649
3980
12:36
hostilities, primarily from the repressed memory therapists,
248
744629
4901
12:41
who felt under attack,
249
749530
1676
12:43
and by the patients whom they had influenced.
250
751206
3528
12:46
I had sometimes armed guards at speeches
251
754734
2937
12:49
that I was invited to give,
252
757671
1905
12:51
people trying to drum up letter-writing campaigns to get me fired.
253
759576
4217
12:55
But probably the worst
254
763793
1981
12:57
was I suspected that a woman
255
765774
2767
13:00
was innocent of abuse
256
768541
2424
13:02
that was being claimed by her grown daughter.
257
770965
2836
13:05
She accused her mother of sexual abuse
258
773801
3417
13:09
based on a repressed memory.
259
777218
1859
13:11
And this accusing daughter had actually allowed her story
260
779077
2883
13:13
to be filmed and presented in public places.
261
781960
3434
13:17
I was suspicious of this story,
262
785394
2509
13:19
and so I started to investigate,
263
787903
2300
13:22
and eventually found information that convinced me
264
790203
4483
13:26
that this mother was innocent.
265
794686
2289
13:28
I published an exposé on the case,
266
796975
2961
13:31
and a little while later, the accusing daughter
267
799936
3444
13:35
filed a lawsuit.
268
803380
1521
13:36
Even though I'd never mentioned her name,
269
804901
2355
13:39
she sued me for defamation and invasion of privacy.
270
807256
4362
13:43
And I went through nearly five years
271
811618
2723
13:46
of dealing with this messy, unpleasant litigation,
272
814341
6552
13:52
but finally, finally, it was over and I could really
273
820893
3674
13:56
get back to my work.
274
824567
2424
13:58
In the process, however, I became part
275
826991
2485
14:01
of a disturbing trend in America
276
829476
2654
14:04
where scientists are being sued
277
832130
2107
14:06
for simply speaking out on matters of great public controversy.
278
834237
4599
14:10
When I got back to my work, I asked this question:
279
838836
3358
14:14
if I plant a false memory in your mind,
280
842194
2398
14:16
does it have repercussions?
281
844592
1844
14:18
Does it affect your later thoughts,
282
846436
1959
14:20
your later behaviors?
283
848395
2101
14:22
Our first study planted a false memory
284
850496
2027
14:24
that you got sick as a child eating certain foods:
285
852523
3326
14:27
hard-boiled eggs, dill pickles, strawberry ice cream.
286
855849
2999
14:30
And we found that once we planted this false memory,
287
858848
3190
14:34
people didn't want to eat the foods as much
288
862038
2451
14:36
at an outdoor picnic.
289
864489
2260
14:38
The false memories aren't necessarily bad or unpleasant.
290
866749
3873
14:42
If we planted a warm, fuzzy memory
291
870622
2358
14:44
involving a healthy food like asparagus,
292
872980
3021
14:48
we could get people to want to eat asparagus more.
293
876001
3475
14:51
And so what these studies are showing
294
879476
2374
14:53
is that you can plant false memories
295
881850
2115
14:55
and they have repercussions
296
883965
1413
14:57
that affect behavior long after the memories take hold.
297
885378
5085
15:02
Well, along with this ability
298
890463
2424
15:04
to plant memories and control behavior
299
892887
2923
15:07
obviously come some important ethical issues,
300
895810
4181
15:11
like, when should we use this mind technology?
301
899991
3059
15:15
And should we ever ban its use?
302
903050
3680
15:18
Therapists can't ethically plant false memories
303
906730
2783
15:21
in the mind of their patients
304
909513
1587
15:23
even if it would help the patient,
305
911100
2564
15:25
but there's nothing to stop a parent
306
913664
1622
15:27
from trying this out on their overweight or obese teenager.
307
915286
4449
15:31
And when I suggested this publicly,
308
919735
2605
15:34
it created an outcry again.
309
922340
3346
15:37
"There she goes. She's advocating that parents lie to their children."
310
925686
4033
15:41
Hello, Santa Claus. (Laughter)
311
929719
2245
15:43
I mean, another way to think about this is,
312
931964
9497
15:53
which would you rather have,
313
941461
2033
15:55
a kid with obesity, diabetes, shortened lifespan,
314
943494
3029
15:58
all the things that go with it,
315
946523
1532
16:00
or a kid with one little extra bit of false memory?
316
948055
3016
16:03
I know what I would choose for a kid of mine.
317
951071
3391
16:06
But maybe my work has made me different from most people.
318
954462
3977
16:10
Most people cherish their memories,
319
958439
2079
16:12
know that they represent their identity,
320
960518
2154
16:14
who they are, where they came from.
321
962672
2025
16:16
And I appreciate that. I feel that way too.
322
964697
2858
16:19
But I know from my work
323
967555
2205
16:21
how much fiction is already in there.
324
969760
4481
16:26
If I've learned anything from these decades
325
974241
2732
16:28
of working on these problems, it's this:
326
976973
2410
16:31
just because somebody tells you something
327
979383
2211
16:33
and they say it with confidence,
328
981594
1575
16:35
just because they say it with lots of detail,
329
983169
2680
16:37
just because they express emotion when they say it,
330
985849
2759
16:40
it doesn't mean that it really happened.
331
988608
3202
16:43
We can't reliably distinguish true memories from false memories.
332
991810
3865
16:47
We need independent corroboration.
333
995675
3548
16:51
Such a discovery has made me more tolerant
334
999223
3090
16:54
of the everyday memory mistakes
335
1002313
2139
16:56
that my friends and family members make.
336
1004452
2914
16:59
Such a discovery might have saved Steve Titus,
337
1007366
4534
17:03
the man whose whole future was snatched away
338
1011900
3576
17:07
by a false memory.
339
1015476
2238
17:09
But meanwhile, we should all keep in mind,
340
1017714
2816
17:12
we'd do well to,
341
1020530
1636
17:14
that memory, like liberty,
342
1022166
3871
17:18
is a fragile thing.
343
1026037
3694
17:21
Thank you. Thank you.
344
1029731
2938
17:24
Thank you. (Applause)
345
1032669
2728
17:27
Thanks very much. (Applause)
346
1035397
3719
ABOUT THE SPEAKER
Elizabeth Loftus - False memories scholarMemory-manipulation expert Elizabeth Loftus explains how our memories might not be what they seem -- and how implanted memories can have real-life repercussions.
Why you should listen
Elizabeth Loftus altered the course of legal history by revealing that memory is not only unreliable, but also mutable. Since the 1970s, Loftus has created an impressive body of scholarly work and has appeared as an expert witness in hundreds of courtrooms, bolstering the cases of defendants facing criminal charges based on eyewitness testimony, and debunking “recovered memory” theories popular at the time, as in her book The Myth of Repressed Memory: False Memories and Allegations of Sexual Abuse (with Katherine Ketcham).
Since then, Loftus has dedicated herself to discovering how false memories can affect our daily lives, leading her to surprising therapeutic applications for memory modification -- including controlling obesity by implanting patients with preferences for healthy foods.
Elizabeth Loftus | Speaker | TED.com