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'We can implant entirely false
You were abducted by aliens, you saw Bugs Bunny at Disneyland, and then
you went up in a balloon. Didn't you? Laura Spinney on our remembrance of
By Laura Spinney, The Guardian (UK), Dec. 3, 2003
To see this story with its related links on the Guardian Unlimited site, go
Alan Alda had nothing against hard-boiled eggs until last spring. Then the
actor, better known as Hawkeye from M*A*S*H, paid a visit to the University
of California, Irvine. In his new guise as host of a science series on
American TV, he was exploring the subject of memory. The researchers showed
him round, and afterwards took him for a picnic in the park. By the time he
came to leave, he had developed a dislike of hard-boiled eggs based on a
memory of having made himself sick on them as a child - something that never
Alda was the unwitting guinea pig of Elizabeth Loftus, a UCI psychologist
who has been obsessed with the subject of memory and its unreliability since
Richard Nixon was sworn in as president. Early on in her research, she would
invite people into her lab, show them simulated traffic accidents, feed them
false information and leading questions, and find that they subsequently
recalled details of the scene differently - a finding that has since been
replicated hundreds of times.
More recently, she has come to believe that lab studies may underestimate
people's suggestibility because, among other things, real life tends to be
more emotionally arousing than simulations of it. So these days she takes
her investigations outside the lab. In a study soon to be published, she and
colleagues describe how a little misinformation led witnesses of a terrorist
attack in Moscow in 1999 to recall seeing wounded animals nearby. Later,
they were informed that there had been no animals. But before the
debriefing, they even embellished the false memory with make-believe
details, in one case testifying to seeing a bleeding cat lying in the dust.
"We can easily distort memories for the details of an event that you did
experience," says Loftus. "And we can also go so far as to plant entirely
false memories - we call them rich false memories because they are so
detailed and so big."
She has persuaded people to adopt false but plausible memories - for
instance, that at the age of five or six they had the distressing experience
of being lost in a shopping mall - as well as implausible ones: memories of
witnessing demonic possession, or an encounter with Bugs Bunny at
Disneyland. Bugs Bunny is a Warner Brothers character, and as the Los
Angeles Times put it earlier this year, "The wascally Warner Bros. Wabbit
would be awwested on sight", at Disney.
Elizabeth Loftus' research has obvious implications for the reliability of
eyewitness testimony. And it was as a result of her findings that in 1994
she co-wrote her book, The Myth of Repressed Memory, and took a strong stand
in the recovered memory debate of the 90s, for which she was reviled by
those who claimed to have uncovered repressed memories of abuse - alien,
sexual or otherwise.
The American Psychological Association (APA) now takes the line that most
people who were sexually abused as children remember all or part of what
happened to them, and that it is rare (though not unheard of) that people
forget such emotionally charged events and later recover them. But it states
that, "Concerning the issue of a recovered versus a pseudomemory, like many
questions in science, the final answer is yet to be known." And the debate
simmers on. Several new lines of evidence suggest that the interaction
between memory and emotion is more complex than was thought. Powerful
emotions, it seems, can both reinforce and weaken real memories. We may be
able to actively degrade painful memories. And false memories, once
accepted, can themselves elicit strong emotions and thereby mimic real ones.
To try to tease apart these complex relationships, the psychologist Daniel
Wright and his colleagues at the University of Sussex have been looking into
what it is that makes some people more susceptible to false memories than
others. On average, studies show that around a third of those subjected to
the "misinformation effect" wholly or partially adopt a false memory, but it
seems to depend on both the person and the memory. Alan Alda swallowed the
hard-boiled egg story, to the extent that he declined to eat one at the UCI
picnic, but he wasn't taken in by Bugs Bunny in Disneyland. In one study
published last year, 50% of volunteers were persuaded they had taken a ride
in a hot-air balloon when they had not. But when Kathy Pezdek of the
Claremont Graduate University, California, tried to make people believe they
had received a rectal enema, she met with almost universal resistance.
Amid all this variability, Wright's group did find one significant correla
tion - though it was not dramatic: those who were more vulnerable to false
memories also tended to suffer more frequent lapses in attention and memory.
The trouble is, he says, "People who have been traumatised also tend to
score higher on tests of lapses in memory." Their traumatic experiences may
contribute to their forgetfulness, but their forgetfulness may lay them open
to memory distortion - so true and false become harder to disentangle.
Among the symptoms suffered by victims of post-traumatic stress disorder (PTSD)
are chilling flashbacks. But, says Michael Anderson of the University of
Oregon, "People who suffer PTSD represent a very small fraction of the
people who experience trauma. The great majority of people who experience
trauma never develop PTSD and eventually are able to adapt in the face of
these events." He argues that they do so by suppressing the memory, and that
this suppression gradually erases it.
Two years ago, Anderson's group showed that people who deliberately try to
keep a word out of their mind find it harder to recall later than if they
had not suppressed it. Counter- intuitively, this form of forgetting seems
more likely to occur when people are confronted by reminders of the very
memory they want to avoid. Anderson says an extreme example of this might be
a child who is forced to live with an abusing care-giver, and must put the
memory of abuse to one side in order to interact with that care-giver. "If
people continue to work at it, the amount of forgetting grows with
repetition and time," he says.
At the annual meeting of the US Society for Neuroscience in New Orleans last
month, Anderson's group presented new data on how this "motivated
forgetting" might arise in the brain. When people tried to suppress memories
for certain words while having their brains scanned in a magnetic resonance
imaging machine, not only did the researchers see a dampening of activity in
the hippocampus, a structure known to be critical for memory formation, but
the frontal cortex was highly active. Since the frontal cortex is important
for conscious control, they believe that neurons here may be suppressing the
representation of the unwanted word in the hippocampus, and in the process
impairing its memory.
However, Anderson admits that his experiments ignore the effect of a
memory's emotional intensity on a person's ability to suppress it. And there
is plenty of evidence that memory for emotionally charged events can be
enhanced - albeit at a cost. Also last month, Bryan Strange of the Wellcome
department of imaging neuroscience at University College London and
colleagues showed that people were more likely to remember a word if it was
emotionally arousing - "murder" or "scream", say - than if it was neutral.
And the words most likely to be forgotten were neutral ones presented just
before emotionally arousing ones. The effect was more pronounced in women
than in men, and both the enhanced memory for the emotional word and the
forgettability of the preceding neutral one could be reversed by dosing the
volunteers in advance with the drug propranolol.
Propranolol, a commonly prescribed beta-blocker, interferes with the
neurochemical pathway thought to be responsible for making emotionally
arousing events more memorable - the beta-adrenergic system - and it has
already been used experimentally in the treatment of patients with PTSD. In
one study, published in October, Guillaume Vaiva of the University of Lille
and colleagues offered prop- ranolol to victims of assault or motor
accidents shortly after their traumatic experience, and then invited them
back for psychological testing two months later. On their return, almost all
the patients exhibited some symptoms associated with PTSD, but they were
twice as severe among those who had not taken the drug.
The finding that propranolol can be effective at blocking memory when given
after an event as well as before is important because, as Loftus explains,
"In the real world you can't be there to exert your manipulations right at
the time an event is happening, but you can get on the scene later." It has
been proposed that propranolol should be offered to victims of rape as a
standard measure to prevent them developing PTSD. But could it also be used
to erase false memories - for instance, "recovered" memories of alien
abduction - that nevertheless elicit all the physiological responses
associated with harrowing, real memories?
"If the formation of false memories depends on beta-adrenergic activation,
then it would seem very possible that propranolol administration could
affect them," says the UCI neuro- biologist Larry Cahill, who has also
investigated the effects of the drug in PTSD patients. But Ray Dolan of UCL,
a co-author with Bryan Strange of the study on memory for emotional words,
points out that not all false memories have a common basis. If they are
interpolations into gaps in memory, such as the gap that opened up before
the presentation of an emotionally arousing word, or possibly the gap into
which Alan Alda inserted a memory of having over-indulged in eggs, then it
is conceivable the drug would work. But, says Dolan, "Other classes of false
memory, for example, where the memories are fantasies or out-and-out
fabrications, would be immune to propranolol."
The idea of doctors having the power to wipe the memory clean sends shivers
down many people's spines. False memories could safely be erased, perhaps,
assuming there was a reliable way of differentiating them from true ones.
Although brain-imaging techniques highlight some differences in patterns of
brain activation when a person recalls a true as opposed to a false memory,
these are statistical differences only. "We are so far away from being able
to use these techniques to reliably classify a single memory as being real
or not real," says Loftus, "Yet that is what the courts have to do."
True memories, too, can get out of control and become destructive, leading
to PTSD and other anxiety disorders. But they start out as an important
self-defence mechanism - teaching you, for instance, that too many
hard-boiled eggs are bad for you. Erasing them completely could be
In the end, says Loftus, it will come down to personal choice. "What would
you rather be in the world, sadder but wiser, all too well remembering the
horrors of your past and feeling depressed, or perhaps not remembering them
very much and being a little happier?"
The Myth of Repressed Memory by Dr Elizabeth Loftus and Katherine
Ketcham, 1996 paperback (St Martin's Press, New York). ISBN 0312141238
American Psychological Association website with links to questions and
answers about memories of childhood abuse:
Suppressing unwanted memories by executive control by Michael C
Anderson and Collinn Green, Department of Psychology, University of Oregon,
2001 (Nature, 410 , 366-9)
Copyright Guardian Newspapers Limited