False memories, failing recall are not an inevitable consequence of
aging, research suggests
Aug. 11, 2003 — In his old age, American humorist Mark Twain once
mused that his mental faculties had decayed such that he could remember only
things that never happened.
"When I was younger, I could remember anything, whether it happened or
not," Twain wrote. "But my faculties are decaying now and soon I shall be so
I cannot remember any but the things that never happened. It is sad to go to
pieces like this, but we all have to do it."
Modern science has confirmed Twain's conjecture — research shows that
memory skills tend to decline dramatically in old age, with decreasing
levels of accuracy and increasing errors. However, new research from
Washington University in St. Louis suggests age-related cognitive decay may
not be as inevitable as Twain contended.
"Our study suggests that the failing memories of older adults, including
their tendency to remember things that never happened, are not an inevitable
consequence of aging," said Henry L. "Roddy" Roediger III, study co-author
and the James S. McDonnell Distinguished University Professor at Washington
University.
In research to be presented Aug. 8 at the American Psychological
Association meeting in Toronto, Roediger provides evidence that false
memories and other cognitive declines often associated with normal aging can
be more directly linked to measurable declines in executive control
functions in the frontal lobes of the brain.
"We tested a group of adults with an average age of 75 years and found
that about one out of four had managed to avoid the memory declines so
common in older adults," said Roediger. "Older adults who maintain high
frontal lobe function were shown to have memory skills every bit as sharp as
a group of college students in their early 20s."
Roediger, a leading expert on human memory, has focused recent research
on understanding cognitive processes behind the creation of false memories,
also known as memory illusions. Human memory, he explains, is not a
storehouse of crystal clear, video images available for immediate and 100
percent accurate recall. Instead, memories are recalled through a
constructive process that retrieves sights, sounds, words and other
seemingly pertinent information, weighs their relevance to the memory task
at hand, and then weaves them into a "best available" representation of a
past experience.
Veridical memories are those that generally conform to reality --
memories that provide a relatively true and accurate representation of a
past experience. False memories occur when we remember events differently
from the way they occurred, or in the most dramatic cases, when we remember
events that never happened. False memories often result when we mistakenly
merge elements of various past experiences or when imagination is used to
fill holes in a sketchy recollection.
"There has been a lot of research in recent years that suggests
deterioration in the prefrontal cortex is linked to age-related declines in
veridical memory, but this is the first study to firmly establish a similar
link to increases in false memories," Roediger said. "The idea that frontal
lobe decline is associated with susceptibility to false memories is
relatively new."
Although we're all susceptible to false memories, the increased
vulnerability associated with aging has serious implications for day-to-day
challenges faced by older adults. Those on daily medications often admit
difficulty recalling whether or not they took a scheduled dose.
Telemarketing scams aimed at the elderly often are fashioned to take
advantage of failing memory skills. And, while the elderly are more likely
to be targets of crime, their susceptibility to false memories might raise
doubts about their ability to provide eyewitness testimony in court cases.
When it comes to memory, it's clear that all people are not created
equal. Test the memory skills of a random sampling of young healthy adults
and you'll find wide individual differences in memory abilities. Test older
adults and you'll find that this variance in individual skills levels has
grown much greater. Interestingly, while some older adults hold onto their
memories, exhibiting skills on a par with the average young adult, other
older adults show dramatic declines.
Several theories exist for why false memories increase with age. One
suggests that older adults fail to properly encode information as an event
is experienced or have problems retrieving and sorting through such details
during recall - a problem known as source monitoring.
A related theory suggest frontal lobe problems make it difficult for
older adults to focus attention on the memory task at hand and to
effectively place retrieved information in the proper context. That is,
frontal lobe functioning underlies the ability to monitor accurately the
source of information, and when frontal lobe functioning declines, so does
memory for the source of the events.
"If the frontal lobes are responsible for controlling attention or source
monitoring, such that false memories can be distinguished from true
memories, then we thought it possible that older adults with high frontal
lobe function scores would not show greater false recall," Roediger said.
"The idea here is that the increased susceptibility for memory illusions
with older adults is carried by older adults with relatively low frontal
lobe function. Our findings support this theory."
Previous research has attempted to establish a clear link between
diminished frontal lobe function and increased false memories, but these
experiments may have failed, suggests Roediger, because methods used did not
effectively assess whether an older adult had relatively high or low frontal
lobe function.
Roediger's team addressed this issue by assessing each participant using
a composite score from performance on a battery of five neuropsychological
tests, each previously shown to measure some facet of frontal lobe function.
Once categorized as high- or low-function, older adults in the study were
tested again to see how each fared in experiments designed to lure them into
the creation of false memories.
In one test, researchers used a standard list of 22 bird names that
people mention most often when asked to list as many types of birds as they
can recall. Researchers provided subjects with the names of 17 birds drawn
from the norm, but left out the five most-often mentioned bird names. Later,
when asked if the name of a particular bird had been presented, some
participants developed a false memory --recalling one or more of the top
five bird names as included in the original list.
In another experiment, researchers created an eyewitness scenario by
showing a video of a workman stealing a wallet from an office desk.
Researchers then interviewed subjects and casually introduced some
misinformation about what was seen on the video. Some subjects took the lure
and included the misinformation in their "eyewitness" accounts of how the
robbery took place.
As a benchmark, researchers conducted the same tests on a group of
college students in their early 20s. Surprisingly, older adults with high
frontal lobe function performed virtually as well as their young
counterparts, both in terms of recalling real events and in avoiding traps
designed to induce false memories.
Although the study identified significant differences in memory
performance among older adults with relatively high or low frontal lobe
function, it's important to note that each of the 36 older adults in this
study might be considered as high functioning when compared to the general
population of older adults, Roediger said.
"Our older adult study group includes many retired academics and most
have high levels of education. All of them drove themselves to the
experiments and were excited to be taking part," Roediger said. "On measures
of knowledge, such as vocabulary, many of the older adults in our study
outscored the college students. "
Thus, while this study found that one-in-four adults had memory skills as
sharp as college students, that ratio most likely would not hold true in the
general population. Skill levels are likely to be much different in a sample
of older adults at the local nursing home.
"In terms of appearance, conversation skills and other surface measures,
it's very difficult on first impression to tell which of the older adults in
this study have high frontal lobe function and which have relatively lower
function," Roediger said.
"Although the differences are subtle, it is interesting to speculate as
to why some of these older adults have been able to retain their executive
processing skills. It's possible that those with diminished cognitive
functioning are on their way to developing Alzheimer's, but it's impossible
to say based on this experiment."
In future research, Roediger and colleagues will be looking for clues
about what is causing age-related declines in frontal lobe function. They
also hope to identify and test techniques that could help older adults
compensate for age-related exaggerations in memory illusions.
Gerry Everding - Washington University In St. Louis |
