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2009-02-10 12:30:22
LiveScience.com Livescience Staff
livescience.com Mon Feb 9, 11:01 am ET
Sometimes when you think you're guessing, your brain may actually know better.
After conducting some unique memory and recognition tests, while also recording
subjects' brain waves, scientists conclude that some gut feelings are not just
guesswork after all. Rather, we access memories we aren't even aware we have.
"We may actually know more than we think we know in everyday situations, too,"
said Ken Paller, professor of psychology at Northwestern University and
co-researcher on the study. "Unconscious memory may come into play, for
example, in recognizing the face of a perpetrator of a crime or the correct
answer on a test. Or the choice from a horde of consumer products may be driven
by memories that are quite alive on an unconscious level."
The findings were published online Sunday in the journal Nature Neuroscience.
The research, done with only a couple dozen participants, adds to a growing
body of conflicting evidence about decision-making. In one study done in 2007,
researchers found that quick decisions were better than those given lots of
thought. But a study last year suggested neither snap judgments nor "sleeping
on it" trump good old-fashioned conscious thought.
The new study
During the first part of the memory test in the new study, participants were
shown a series of colorful kaleidoscope images that flashed on a computer
screen. Half of the images were viewed with full attention as participants
tried to memorize them. While viewing the other half, the participants were
distracted: They heard a spoken number that they had to keep in mind until the
next trial, when they indicated whether it was odd or even.
In other words, they could focus on memorizing half of the images but were
greatly distracted from memorizing the others.
A bit later, they viewed pairs of similar kaleidoscope images in a recognition
test.
"Remarkably, people were more accurate in selecting the old image when they had
been distracted than when they had paid full attention," Paller said. "They
also were more accurate when they claimed to be guessing than when they
registered some familiarity for the image."
Splitting attention during a memory test usually makes memory worse.
"But our research showed that even when people weren't paying as much
attention, their visual system was storing information quite well," Paller
said.
The brain's role
During the tests, electrical signals in the brain were recorded from a set of
electrodes placed on each person's head. The brain waves during implicit
recognition were distinct from those associated with conscious memory
experiences. A unique signal of implicit recognition was seen a quarter of a
second after study participants saw each old image.
Other related research has shown that amnesia victims with severe memory
problems often have strong implicit memories, Paller and his colleague, Joel L.
Voss of the Beckman Institute, said in a statement.
"Intuition may have an important role in finding answers to all sorts of
problems in everyday life," Paller said.