'We can implant entirely false memories' - Thursday December 4, 2003
The Guardian

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 things past

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 happened.

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 dangerous.

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?"

Further reading

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: www.apa.org/pubinfo/

Suppressing unwanted memories by executive control by Michael C
Anderson and Collinn Green, Department of Psychology, University of
Oregon, 2001 (Nature, 410 [6826], 366-9)

http://www.guardian.co.uk/life/feature/story/0,13026,1098943,00.html