The New York Times

June 27, 2008
Op-Ed Contributor
Your Brain Lies to You
By SAM WANG and SANDRA AAMODT

FALSE beliefs are everywhere. Eighteen percent of Americans think the
sun revolves around the earth, one poll has found. Thus it seems
slightly less egregious that, according to another poll, 10 percent of
us think that Senator Barack Obama, a Christian, is instead a Muslim.
The Obama campaign has created a Web site to dispel misinformation.
But this effort may be more difficult than it seems, thanks to the
quirky way in which our brains store memories — and mislead us along
the way.

The brain does not simply gather and stockpile information as a
computer's hard drive does. Facts are stored first in the hippocampus,
a structure deep in the brain about the size and shape of a fat man's
curled pinkie finger. But the information does not rest there. Every
time we recall it, our brain writes it down again, and during this
re-storage, it is also reprocessed. In time, the fact is gradually
transferred to the cerebral cortex and is separated from the context
in which it was originally learned. For example, you know that the
capital of California is Sacramento, but you probably don't remember
how you learned it.

This phenomenon, known as source amnesia, can also lead people to
forget whether a statement is true. Even when a lie is presented with
a disclaimer, people often later remember it as true.

With time, this misremembering only gets worse. A false statement from
a noncredible source that is at first not believed can gain
credibility during the months it takes to reprocess memories from
short-term hippocampal storage to longer-term cortical storage. As the
source is forgotten, the message and its implications gain strength.
This could explain why, during the 2004 presidential campaign, it took
some weeks for the Swift Boat Veterans for Truth campaign against
Senator John Kerry to have an effect on his standing in the polls.

Even if they do not understand the neuroscience behind source amnesia,
campaign strategists can exploit it to spread misinformation. They
know that if their message is initially memorable, its impression will
persist long after it is debunked. In repeating a falsehood, someone
may back it up with an opening line like "I think I read somewhere" or
even with a reference to a specific source.

In one study, a group of Stanford students was exposed repeatedly to
an unsubstantiated claim taken from a Web site that Coca-Cola is an
effective paint thinner. Students who read the statement five times
were nearly one-third more likely than those who read it only twice to
attribute it to Consumer Reports (rather than The National Enquirer,
their other choice), giving it a gloss of credibility.

Adding to this innate tendency to mold information we recall is the
way our brains fit facts into established mental frameworks. We tend
to remember news that accords with our worldview, and discount
statements that contradict it.

In another Stanford study, 48 students, half of whom said they favored
capital punishment and half of whom said they opposed it, were
presented with two pieces of evidence, one supporting and one
contradicting the claim that capital punishment deters crime. Both
groups were more convinced by the evidence that supported their
initial position.

Psychologists have suggested that legends propagate by striking an
emotional chord. In the same way, ideas can spread by emotional
selection, rather than by their factual merits, encouraging the
persistence of falsehoods about Coke — or about a presidential candidate.

Journalists and campaign workers may think they are acting to counter
misinformation by pointing out that it is not true. But by repeating a
false rumor, they may inadvertently make it stronger. In its concerted
effort to "stop the smears," the Obama campaign may want to keep this
in mind. Rather than emphasize that Mr. Obama is not a Muslim, for
instance, it may be more effective to stress that he embraced
Christianity as a young man.

Consumers of news, for their part, are prone to selectively accept and
remember statements that reinforce beliefs they already hold. In a
replication of the study of students' impressions of evidence about
the death penalty, researchers found that even when subjects were
given a specific instruction to be objective, they were still inclined
to reject evidence that disagreed with their beliefs.

In the same study, however, when subjects were asked to imagine their
reaction if the evidence had pointed to the opposite conclusion, they
were more open-minded to information that contradicted their beliefs.
Apparently, it pays for consumers of controversial news to take a
moment and consider that the opposite interpretation may be true.

In 1919, Justice Oliver Wendell Holmes of the Supreme Court wrote that
"the best test of truth is the power of the thought to get itself
accepted in the competition of the market." Holmes erroneously assumed
that ideas are more likely to spread if they are honest. Our brains do
not naturally obey this admirable dictum, but by better understanding
the mechanisms of memory perhaps we can move closer to Holmes's ideal.

Sam Wang, an associate professor of molecular biology and neuroscience
at Princeton, and Sandra Aamodt, a former editor in chief of Nature
Neuroscience, are the authors of "Welcome to Your Brain: Why You Lose
Your Car Keys but Never Forget How to Drive and Other Puzzles of 

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