When A Lie Becomes Memory's Truth:
Memory Distortion After Exposure to
Misinformation^
Elizabeth F. Loftus
What happens when people witness an event, say, a crime or accident, and are later exposed to new
information about that event? Two
decades of research have been devoted to the influence of new information on the recollections of such
witnesses. An all-too-common findIng is that after receipt of new information that is misleading in some
way, people make errors when they
report what they saw. New,
postevent information often becomes incorporated into a recollection, supplementing or altering it,
sometimes in dramatic ways. New
information invades us, like a Trojan
horse, precisely because we do not
detect its influence. Understanding
how we become tricked by revised
data about a witnessed event is a
central goal of this research.
Current research showing how
memory can become skewed when
peopie assimilate new data utilizes a
simple paradigm. Participants first
witness a complex event, such as a
simulated violent crime or automobile accident. Subsequently, half the
participants receive new, misleading information about the event. The
other half do not get any misinforElizabeth F. Loftus is Professor of
Psychology at the University of
Washington. Her most recent book
is Witness for the Defense: The Accused, the Eyewitness, and the Expert Who Puts Memory on Trial,
coauthored with K. Ketcham (St.
Martin's Press, 1991). Address
correspondence to E. Loftus, Department of Psychology, University of Washington, Seattle, WA
98195; e-mail: eloftusCamilton.
u.Washington.edu.
mation. Finally, all participants attempt to recall the original event. In
a typical example of a study using
this paradigm, participants saw a
simulated traffic accident. They then
received written information about
the accident, but some people were
misled about what they saw. A stop
sign, for instance, was referred to as
a yield sign. When asked whether
they originally saw a stop or a yield
sign, participants given the phony
information tended to adopt it as
their memory; they said they saw a
yield sign."^ In these and many other
experiments, people who had not
received the phony information had
much more accurate memories. In
some experiments, the deficits in
memory performance following receipt of misinformation have been
dramatic, with performance differences as large as 30% or 40%.
This degree of distorted reporting
has been found in scores of studies,
involving a wide variety of materials. People have recalled seeing
nonexistent items, such as broken
glass, tape recorders, and even
something as large and conspicuous
as a barn (in a bucolic scene that
contained no buildings at all), and
have recalled incorrect traits for
items they did see, such that a cleanshaven man developed a mustache,
straight hair became curly, a stop
sign became a yield sign, and a
hammer became a screwdriver, in
short, misleading postevent information can alter a person's recollection
in a powerful, even predictable,
manner.
The change in report arising after
receipt of misinformation is often referred to as the misinformation effect.'' Four questions about the mis-
Copyfight '& 1332 Americdn Pt,ychologjt:al Society
information effect have occupied the
attention of researchers:
1. When are people particularly
susceptible to the damaging influence on recollection of misleading information, and when
are people particularly resistant?
2. What groups of people are particularly prone to having their
recollections be modified, and
what groups are resistant?
3. Does misinformation actually impair a person's ability to remember details of an event? Put another way, what happens to the
original memory after exposure
to misinformation?
4. Do people genuinely believe in
the misinformation?
WHEN ARE PEOPLE
SUSCEPTIBLE TO
MISINFORMATION?
A growing body of studies reveals
the conditions that make people particularly susceptible to the influence
of misinformation. For example,
people are particularly prone to having their memories modified when
the passage of time allows the original memory to fade. Put another
way, with a long interval between
the event and the misinformation,
the injection of misinformation becomes relatively easy. In its weakened condition, memory—like the
disease-ridden body—becomes especially vulnerable to repeated assaults on its very essence. This finding leads us to a principle, the
discrepancy detection principle, for
determining when changes in recollection will occur:
Recollections are more likely to
change if a person does not immediately
detect discrepancies between postevent
information and memory for the original
event.
Other lines of research fit well
with the discrepancy detection principle. For example, if people are exposed to misinformation that is sub-
tie, they are more likely to be
influenced than if the misinformation is not subtle. Consider the simple interrogative sentence "Was the
mustache worn by the tall intruder
light or dark brown?" This sentence
not so subtly suggests the existence
of a mustache. By comparison, "Did
the intruder who was tail and had a
mustache say anything to the professor?" is more subtle in its suggestion
of the mustache, having embedded
this idea in a relative clause. People
are more likely to falsely claim that
they saw a mustache when exposed
to the more subtle version.
Another line of research that fits
well with the discrepancy detection
principle involves explicit warnings.
If people are warned prior to a
postevent narrative that the narrative
may be misleading, they are better
able to resist its influence than if they
are not warned. In these various
lines of research, the subject's detection of discrepancies between the
original memory and the postevent
passage (or failure to detect discrepancies) appears to be crucial. With a
long interval between event and
misinformation, and with misinformation that is subtly embedded, the
ability of subjects to detect a discrepancy is minimized. !n contrast,
when subjects are warned about the
likelihood of incorrect information,
they scrutinize the postevent information, and the likelihood of detection of a discrepancy is enhanced. It is
also true that people are particularly
susceptible if they can be induced to
repeat the misinformation as fact.
WHO IS SUSCEPTIBLE
TO MISINFORMATION?
The majority of the studies of the
misinformation effect have been
conducted with college students,
and few individual difference variables have emerged. Where group
differences do emerge is in misinformation studies using children as subjects. It is common (although not
universal) to find that young children
are especially susceptible to these
manipulations.'^
The largest study of individual differences was recently conducted
with nearly 2,000 people who were
attending a science museum in San
Francisco.^ The experiment was one
of the interactive exhibits at the museum, which means that subjects
provided data for the experiment
while learning from the exhibit. All
subjects watched a short film clip
and later answered a series of questions about it. Some subjects were
exposed to misleading questions but
others were not, so that the impact
of misinformation could be assessed. The most important demographic variable was the age of the
subject, which varied between 5
and 75. Memory performance rose
as a function of age up to the 20s,
leveled off, and then fell sharply for
subjects over age 65. Moreover, the
youngest and the oldest groups
showed large misinformation effects. Put another way, the very
young and the elderly were significantly more accurate when not misinformed than when misinformed, a
result that is consistent with other
age effects in the literature on episodic memory. The article describing the study also reviews relevant
literature on individual differences
in susceptibility to misinformation.^
WHAT HAPPENS TO THE
ORIGINAL MEMORY?
An important issue that has been
debated is whether misinformation
actually impairs a person's ability to
remember details of an event. Put
another way, are memory traces altered by postevent misinformation?
There are several ways in which misinformation could impair memory.
First, misinformation could cause
trace impairment; that is, it could
update or alter the previously
formed memory. New information
could combine with earlier traces to
Published by Cambridge University
change the representation. Second,
misinformation could cause retrieval
impairment; that is, misinformation
could make the original memory
trace less accessible without altering
it.^ Impairment of some sort is implied by either the trace impairment or the retrieval impairment
mechanism.
Some theorists have rejected the
notion that misinformation impairs
memory. McCloskey and Zaragoza^
disagreed with the idea that the misinformation effect is due to recoding
processes or updating of previously
stored memories or arises because
inhibition or suppression renders the
older memory less accessible. McCloskey and Zaragoza argued instead that the misinformation does
not affect memory at all, but merely
influences the reports of subjects
who have never encoded (or do not
recall} the original event. Instead of
guessing blindly, these subjects use
the misinformation to decide what to
report as their memory. Misinformation effects could also be obtained if
subjects remember both sources of
information but select the misleading information because they conclude it must be correct.
Several lines of evidence support
the notion that misinformation occasionally does impair the ability to remember original details, however.
One kind of evidence involves studies using tests that do not permit the
misinformation option. Say a subject
originally saw a stop sign, but it was
later referred to as a yield sign. Suppose we now give the subject a test
that does not permit the selection of
the yield sign (e.g., the choice is between a stop sign and a no-parking
sign). If the misinformation has impaired memory for the stop sign,
then the misinformed subjects
would be less likely to remember the
stop sign than the control subjects. If
there has been no memory impairment due to misinformation, then
misled subjects would be expected
to be as accurate as control subjects
on a test of this type. Although some
studies do show equal performance,
there are several published demonstrations of deficits in performance
with this restrictive type of test. One
study"* presented preschool children
with stories and found impairment
following misinformation. Another
study** presented adult subjects with
visual scenes (e.g., nature scenes including ponds, flowers, mountains)
and then provided similar visual
scenes as postevent information.
Subjects who received misinformation were less able than control subjects to discriminate the original
scenes from novel distractors.
A second line of work supporting
a memory impairment interpretation
involves the use of a yes-no test.'*
Belli showed subjects a simulated
crime via slides and then fed them
some misinformation via a postevent
narrative that they read under a pretense. Finally, subjects were presented with a series of statements,
each dealing with a critical item
from the crime. Subjects said "yes"
if they saw the item in the slides and
" n o " otherwise. Compared with
memories for control items, there
was a large reduction in accurate
memory for the items about which
subjects had received misinformation. The large reduction was not
offset by the small improvement in
memory for completely novel items.
Other lines of research that are
consistent with memory impairment
involve implicit memory testing'"
and logic-of-opposition procedures
(described in the next section). Although any of these findings might
be readily explained by alternative
interpretations, taken together, these
studies support the idea that misinformation can impair a subject's
ability to remember original details.
DO PEOPIE GENUINELY
BELIEVE IN
THE MISINFORMATION?
One reason to think that subjects
truly believe in their misinformation
memories is that they often express
these memories with a great deal of
confidence. But how can we rule
out the possibility that subjects report misinformation memories to appear observant or prove they are
"good" subjects?
The logic-of-opposition paradigm, developed by Jacoby and applied to the study of misleading suggestions by Lindsay," provides an
ideal means of assessing what subjects really believe. By instructing
his subjects that any information
contained in the postevent narrative
was wrong and should not be reported on the test, Lindsay set the
tendency to report suggested details
in opposition to the ability to remember the details from the
postevent narrative. Put another
way, he tried to offset subjects' tendency to want to report an item they
remembered reading by harshly
warning the subjects not to report
anything they remembered from the
reading. If subjects continued to
base their test responses on suggested items, despite explicit instructions against doing so, Lindsay
could conclude that misled subjects
truly believe that they saw the suggested details at the time of the initial event. In fact, Lindsay obtained
such results. He first showed an
event via slides, and later provided
misinformation about some items.
Misinformed subjects who saw the
slides and read the narrative in the
same session claimed to have seen
the misinformation in the slides 27%
of the time, compared with 9%
for subjects who had not been
misinformed.
CONCLUDING REMARKS
Misleading information can turn a
lie into memory's truth. It can cause
people to believe that they saw
things that never really existed, or
that they saw things differently from
the way things actually were. It can
make people confident about these
Copyright © 1992 American Psychological Society
false memories and also, apparently,
impair earlier recollections. Once
adopted, the newly created memories can be believed as strongly as
genuine memories. If handled skillfully, the power of misinformation is
so enormous and sufficiently controllable that a colleague and I recently postulated a not-too-distant
"brave new world" in which misinformation researchers would be able
to proclaim: " 'Give us a dozen
healthy memories . . . and our own
specified world to handle them in.
And we'll guarantee to take any one
at random and train it to become any
type of memory that we might select
. . . regardless of its origin or the
brain that holds it.' "^^ The implications of these findings for the legal
field, for advertising, for political
persuasion, and for clinical settings
are far-reaching.
Notes
1 The author'^ research described in this article
was supported by grants from the National Institute
of Mentai Health, the National Science Foundatron,
and the U.S, Department of Transportation.
2, E.F, Loftus. Eyewdncii TaVmony (Harvard
University Press, Cambridge, MA, 1979).
3, E.F. Loftus and H,C. Hoffman, Misinformation and memory: The creation of new memories,
lourml oi Experinmntal Psycho/ogy: Genera/, 118,
100-104 (1989),
4, SJ, Ceci, D.F. Rosi, and M.P. Togiia, Suggestibility of children's memory: Psycholegal implications, lourndl of Experimental Psychology: CeneM/, 116, 38-49 (1987),
3 E.F. Loftus, B. Levidow, and S. Duensing,
Who remembers best? Individual differences in
memorv' for events that occurred in a science museum. Applied CogniUve Psychology, 6, 93-107
(1992).
6. |. Morton, R,H, Hammersley, and D.A. Bekerian. Headed records: A model for memory and
its failures, Cogn/!/on, 20, 1-23 (1965).
7. M, McCloskey and M, Zaragoza, Misleading
postevent information and memory for events: Arguments and evidence against memory impairment
hypotheses, journal oi Experimental Psychology
Ceneral, 114, 1-16 (1985).
8. C.C. Chandler, How memory for an event is
influenced by related events: Interference in modified recognition tests, lournal of Experimental Paychotogy: learning, Memory, and Cognition, 17,
115-125 (1991).
9. R.F. Belli, Influences of misleading postevent
information: Misinformation interference and acceptance, lournal of Experimental Psychology: Ceneral, 118, 72-85 (1989).
10. E.F. Loftus, Made in memory, in The Psychology of Learning and Molivation, Vol. 27, G.
Bower, Ed. (Academic Press, Orlando, FL, 1991).
11. D.S. Lindsay. Misleading suggestions can
impair eyewitnesses' ability to remember event details, lournal of Experimental Psychology: Learning,
Memory, and Cognition, )6, 1077-1083 (1990).
12. Loftus and Hoffman, note 3, p. 10:i.