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.