Working memory (WM) is the capacity to store and
manipulate information for brief periods of time. According to
researchers at the University of York, "It provides a mental workspace
that is used in many important activities in learning...and is a pure
measure of a child's learning potential." WM deficits contribute
to difficulties with attention and learning for many children with ADHD
and individuals with poor WM typically make poor academic progress
during the school years. In fact, "...of those children whose WM
abilities fall in the bottom 10%, over 80% have substantial problems in
either reading or mathematics or, most commonly, in both (Gathercole
& Allow, 2008). You can find additional information on Working
Memory and its role in learning and attention at
http://www.york.ac.uk/res/wml/FAQ.htm
Until recently, WM capacity has been believed to be fixed and it seemed
unlikely that the adverse effects of poor WM on learning could be
overcome. However, several recent reports indicate that intensive
training of WM can enhance WM capacity in many individuals and that
this leads to better attention and improvements in daily cognitive
functioning. This research has included randomized-controlled
trials of WM training for children with ADHD, normally developing
preschoolers, adult stroke victims, and healthy younger and older
adults. (The study of WM training for children with ADHD is
reviewed at
www.helpforadd.com/2005/march.htm ). In
an especially intriguing study, WM training was found to improve fluid
intelligence in normal adults - the text of this study can be viewed
online at
www.pnas.org/content/105/19/6829.full.pdf+html?sid=820a43a6-71cf-4563-b0e2-cd208b1de8ee
The authors of the current study reviewed note that "while these early
findings look promising, the educational significance of WM training is
as yet untested." In addition, prior studies of school-age
children were conducted with children diagnosed with ADHD and did not
include youth with poor WM who did not also have ADHD. Thus, the
goals of their study [Holmes. J., Gathercole, S.E., & Dunning, D.L.
(2009). Adaptive training leads to sustained enhancement of poor
working memory in children. Developmental Science] was test whether WM
training helps children with documented WM deficits and whether the
benefits are sufficient to overcome learning difficulties associated
with poor WM.
Participants were 42 eight- to eleven-year-old children attending six
schools in the North-East of England who were selected based on scoring
in the bottom 15% on a validated test of WM. Children were
randomly assigned to one of two conditions - a high intensity (HI) WM
training condition and a low intensity (LI) WM training condition that
served as the control condition. (Note - Children attending the
same school all received the same type of training.)
The HI treatment consisted of performing WM tasks via a computer
program developed called Cogmed Working Memory Training. The WM
tasks visuospatial tasks - remembering the position of objects on the
screen - as well as verbal tasks - remembering sequences of letters,
sounds, and digits. In all cases, children responded to the WM
task by clicking on various choices with the computer mouse.
Each training session provided exposure to 115 WM trials and required
about 35 minutes to complete; training occurred at school during the
regular school day. In the HI condition, the difficulty level of
the WM trials was adjusted to match the WM ability of the child on a
trial-by-trial basis. For example, if a child successfully
recalled three digits in reverse order, on the next trial he had to
recall four. When a trial was failed, the next trial was made
easier by reducing the number of items to be recalled By this
method of 'adaptive training', children were challenged to work at a
level that closely matched their ability and to stretch their WM
capacity by presenting more difficult tasks after easier ones were
successfully passed.
The LI condition was identical to that described above except that the
difficulty of the WM trials remained at a low level throughout, i.e.,
the number of items children were required to recall never increased
beyond two. Thus, these children had the same experience as
children in the HI group, i.e., they spent the same amount of time
engaging in computerized WM tasks, but they were not challenged to
improve. As a result, they were not expected to show the same
improvement in WM as children who received HI treatment.
Both groups of children completed a minimum of 20 training sessions
spread over five to seven weeks.
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Measuring the impact of training
-
The impact of WM training was assessed in several ways. First,
children completed a computerized assessment of WM immediately before
and immediately after training was completed using tasks that differed
from those on which they trained. Prior research has demonstrated
that performance on this WM assessment does not improve the second time
it is taken. Therefore, any gains associated with HI training
would reflect actual gains in WM rather than mere practice
effects.
Standardized measures of IQ and of reading and math were also completed
pre- and post training. The reading test was a measure of single
word reading which does not place demands on WM in the same way that
reading comprehension does. The math test was an assessment of
mathematical reasoning, a task for which WM is more important.
For students who received HI training, a six-month follow-up was also
conducted so that the maintenance of any training related gains could
be determined.
Finally, the researchers devised a following directions task that
represents a practical assessment of WM that is closely linked to what
happens in the classroom. On this task, children listened
to an increasingly long set of directions, e.g., "touch the yellow
pencil and then put the blue ruler in the red folder..." and then had
to perform that designated actions. When they passed a trial, the
number of directions to be followed increased on the next trial.
The test continued until the child was unable to produce the behaviors
in the correct sequence with the number of trials passed to that point
serving as each child's score.
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Results
-
*
Impact on WM *
Children completing the HI training showed significant improvements in
all aspects of WM - both verbal WM and visuo-spatial WM. The
magnitude of their improvement would be considered large by
conventional standards, as the effect sizes were greater than 1.0. In
contrast, control subjects who received LI training did not make
significant gains in either area. Furthermore, 68% of children
receiving HI training had WM scores at post-test that fell in the
normative range compared to only 25% of children in the LI group.
WM gains for the HI group remained significant at the six-month
follow-up. Although the magnitude of the improvements had
diminished slightly, the effect sizes remained in a range that is
considered large by conventional standards.
*
Listening Test *
Similar results were obtained on the task that measured children's
ability to follow spoken directions. Children in the HI group
showed significant improvement at post-test on this task, i.e., they
were able to correctly remember a longer string of instructions, while
those in the control condition were not. The magnitude of the
gains made by HI children would be considered large and remained
evident at the six-month follow-up.
*
IQ and Academic Achievement *
No significant improvements in IQ were found. In addition, no
significant gains in reading or math were evident at post-test.
However, at the six-month follow-up, children who received HI training
showed a significant gain in their mathematical reasoning scores
compared with pre-training baseline levels. The magnitude of this
effect would be considered moderate, i.e., an effect size of .49.
-
Summary and
Implications -
The authors begin their discussion by noting that in a classroom of 30
children, there will typically be four to five who have low WM
abilities that hamper their academic progress. They go on to note
that their study demonstrates that WM deficits and associated learning
difficulties can "...be ameliorated, and possibly even overcome, by
intensive training over a relatively short period." In fact, the
majority of children completing the intensive training improved their
WM substantially and these gains were maintained six months out.
It should be noted that not all outcomes showed improvement following
training. Thus, there were no gains in IQ and gains in word
reading and mathematics reasoning were not evident immediately after
training. The authors suggest the absence of IQ gains indicates
that although IQ and WM are related, the contribution of WM to learning
is not directly linked to IQ. They note that gains in academic
achievement were not anticipated immediately post-training because
achievement gains associated with better WM would be expected to take
time to develop. Indeed, this was found for children's mathematics
reasoning as their achievement scores showed significant improvement
six months after training ended. The absence of benefits on the
reading measure may reflect the fact that the test used - a basic word
reading test - does not depend heavily on WM skills. Had a
reading measure that is more WM dependent been used, i.e., a
comprehension task, perhaps such gains would have
emerged.Of course, this is only speculation and would need to be
documented in subsequent
work.
Although these are encouraging results, there are limitations of the
study that should be noted. First, the sample size - 42 children
- is relatively small and replicating these results with a larger
sample would be important. Second, six month follow-up data was
not collected on children in the control condition, and one cannot be
certain that achievement gains would not have also emerged for this
group. This seems unlikely given that no improvement in WM was found
for control children at the conclusion of training, but cannot be ruled
out entirely.
The study would have also been strengthened by the inclusion of teacher
ratings of children's behavior and academic performance. In a
prior trial of Cogmed WM training in children with ADHD, although
significant improvement in parents' ratings of children's inattentive
behavior was found, similar gains were not reported by teachers.
Thus, it would have been helpful to document whether teachers of
children in this study observed them to show better attention and
academic performance in the classroom.
Despite these limitations, results from this study add to the research
indicating that intensive training of WM can yield important benefits
for children and adults who struggle because of WM deficits. A
number of additional studies of this new cognitive training approach
are currently underway, and will be summarized in future issues of
Attention Research Update as they are published.