Age-Related Deficits in Component Processes of Working Memory
University of California, San Francisco, and University of
Margaret A. Sheridan, Jeffrey W. Cooney, and
University of California, Berkeley
Working memory deficits in normal aging have been well documented, and studies suggest that high
memory load plus the presence of distraction negatively impacts successful memory performance to a
greater degree in older individuals. However, characterization of the component processes that are
impaired by these task manipulations is not clear. In this behavioral study, younger and older subjects
were tested with a delayed-recognition and recall task in which the encoding and delay period were both
manipulated. During the encoding period, the subjects were presented with either a single letter or
multiple letters at their predetermined forward letter span, and the delay period was either uninterrupted
or interrupted with a visual distraction. There was an age-related impairment of working memory
recognition accuracy only in the combination of high memory load and distraction. These results suggest
that when working memory maintenance systems are taxed, faulty recognition processes may underlie
cognitive aging deficits in healthy older individuals.
Keywords: aging, distractor, working memory, delayed-recall task, delayed-recognition task
Memory loss is a frequent complaint in older adults, and it
involves not only difficulty remembering recent events but also
impairments in holding information “in mind” over short periods
of time. The latter cognitive process is referred to as working
memory (WM), and age-related deficits in WM have been dem-
onstrated in many studies (Belleville, Peretz, & Malenfant, 1996;
Dobbs & Rule, 1989; Foos & Wright, 1992; Salthouse, Babcock,
& Shaw, 1991; Wingfield, Stine, Lahar, & Aberdeen, 1988).
WM refers to the temporary representation of information that
was just experienced or just retrieved from long-term memory but
is no longer accessible in the external environment (Baddeley,
1986). These internal representations are short lived but can be
maintained for longer periods of time through active rehearsal or
maintenance strategies, and they can be subjected to various op-
erations that manipulate the information in such a way that makes
it useful for goal-directed behavior. To maintain and manipulate
relevant information that is not accessible in the environment, the
brain needs a storage process as well as rehearsal or maintenance
processes that can prevent the contents of the storage system from
decaying (see, for example, D’Esposito & Postle, 1999).
Although not completely dissociable, these component pro-
cesses of WM can be studied with some degree of isolation with
the help of different task designs. Storage capacity is often as-
sessed by a span test, in which a series of letters, digits, words, or
images are presented to subjects for immediate recall. WM main-
tenance processes are often assessed with delay tasks, which
require subjects to hold information in mind over an interval of
time. In general, storage processes, as assessed by span tasks, are
not affected by normal aging (see, for example, Wingfield et al.,
1988). In contrast, WM maintenance processes, as assessed by
delay tasks, have been found to be impaired in normal aging
(Anders, Fozard, & Lillyquist, 1972; Byrd, 1986; Craik & Rabi-
nowitz, 1985; Nielsen-Bohlman & Knight, 1995). However, not all
studies that have assessed WM maintenance processes have found
age-related impairments (e.g., Boaz & Denney, 1993). Moreover,
in those studies that have found deficits, the precise nature of the
deficit is not clear. There are several possible explanations for the
discrepant findings in the cognitive aging literature. First, in stud-
ies that have not found age-related impairment on delay tasks it is
possible that WM maintenance processes were not sufficiently
taxed. For example, older individuals were not impaired on delay
tasks that required the maintenance of only a single item (Chao &
Knight, 1997; Della-Maggiore et al., 2000). In these studies, im-
pairments may have been observed if more demands had been
placed on WM maintenance processes by increasing the memory
Even in studies that have found an age-related impairment on
delay tasks, it is still plausible that deficits in other processes,
rather than WM maintenance processes, contributed to impairment
on the task. For example, some delay tasks require free recall,
whereas others test by recognition (e.g., Crook & Larrabee, 1992;
Crook & West, 1990). Although both types of delay tasks tap WM
maintenance processes, they differ in the types of cognitive pro-
cesses that are necessary for retrieving information that is being
actively maintained. Thus, impairment in retrieval-related pro-
cesses, rather than maintenance processes, could account for the
age-related impairments that were observed.
Adam Gazzaley, Department of Neurology and Physiology, University
of California, San Francisco, and Helen Wills Neuroscience Institute and
Department of Psychology, University of California, Berkeley; Margaret
A. Sheridan, Jeffrey W. Cooney, and Mark D’Esposito, Helen Wills
Neuroscience Institute and Department of Psychology, University of Cal-
This work was supported by National Institutes of Health Grants
AG025221, MH63901, AG15793, and NS40813; the National Research
Service Award; the American Federation for Aging Research; and the
Veterans Administration Research Service. We thank Marcia Johnson and
Karen Mitchell for helpful comments on the article.
Correspondence concerning this article should be addressed to Adam
Gazzaley, University of California, San Francisco, 1700 4th Street, Byers
2007, Vol. 21, No. 5, 532–539
Copyright 2007 by the American Psychological Association
Finally, in some WM studies, distracting stimuli are presented
during the delay period, resulting in age-related deficits (e.g., Chao
& Knight, 1997). In these studies, the possibility exists that the
age-related deficit is not in WM maintenance processes per se but
in the ability to inhibit or suppress irrelevant information. In fact,
Hasher and Zacks’ (1988) inhibitory deficit hypothesis proposed
that aging leads to an impaired ability to suppress task-irrelevant
information in WM, resulting in performance deficits, and there
are many studies that have supported age-related deficits in inhib-
itory control (Alain & Woods, 1999; Chao & Knight, 1997;
Gazzaley, Cooney, Rissman, & D’Esposito, 2005; Sweeney, Ro-
sano, Berman, & Luna, 2001). In this model of cognitive aging,
WM maintenance processes were not considered to be the source
of age-related WM impairments. Thus, the main purpose of this
study was to precisely characterize the nature of the WM deficits
found in normal aging and to distinguish among these possibilities.
To our knowledge, a behavioral study of normal aging has not
been performed in which individuals have been tested with a delay
task in which WM maintenance processes are taxed at different
load levels, interrupted with distracting stimuli, and tested with
both recall and recognition.
In the current study, we employed a very simple WM mainte-
nance task, in which it was expected that there would be no
performance impairment in older adults (i.e., remembering a single
letter over a short delay without distraction). However, we also
manipulated the task design to assess different processes (e.g.,
maintenance, inhibition, retrieval mode) and evaluate which fac-
tors, or combination of factors, result in impairment. To accom-
plish this, 52 healthy younger and older adults were tested with a
delay task in which both the encoding and delay period were
manipulated and the influence on both recall and recognition
performance was evaluated. During the encoding period, the sub-
jects were presented with either a single letter (low load) or
multiple letters (high load), and the delay period was either unin-
terrupted or interrupted by a distractor (a simple, visual attention
task). Not all subjects were exposed to the same high load, because
the demands of different loads may vary between subjects, espe-
cially across different age groups. Rather, subjects performed the
high load task with the amount of letters equivalent to their
individually predetermined storage capacity.
This experimental design allowed us to tax WM maintenance in
two different manners: by increasing memory load, which introduces
greater rehearsal demands, and by using distraction, which directly
interrupts rehearsal processes. Furthermore, it allowed us to explore
not only the impact of load and distraction on WM maintenance but
also, for the first time, potential interactions between load and dis-
traction on WM performance in older adults. Thus, by exploring the
impact of these manipulations independently and in combination, we
investigated factors that contribute to WM deficits in normal aging.
We hypothesized that the demands of the WM task in both the low
load and distractor-free version would be insufficient to impair per-
formance in older adults but that the combination of these factors
would lead to significant impairment.
Subjects consisted of 26 older adults (ages 60–82 years) and 26
younger adults (ages 18–30 years). Prior to the study, all subjects
were screened for any disorders and/or medication usage that
might affect cognitive functioning. All subjects reported no med-
ical, neurological, or psychiatric disorders and were not taking
medications that had central nervous system actions. This restric-
tion included medications for heart disease, diabetes, and blood
pressure, as well as psychotropic and sleeping medications.
Young adult subjects were recruited primarily from the popu-
lation of undergraduates at the University of California, Berkeley.
Older adult subjects were recruited in and around Berkeley, Cal-
ifornia. None of the older subjects exhibited evidence of depres-
sion as screened by the Beck Depression Inventory (Beck, 1978) or
dementia as documented by a score of 27 or greater on the
Mini-Mental State Exam (Folstein, Folstein, & McHugh, 1975) at
the time of testing. Older subjects were well educated (range ?
14–24 years). All subjects signed informed consent and were paid
for their participation.
Behavioral testing consisted of three parts. First, subjects re-
ceived several neuropsychological tests. Next, they completed a
task designed to assess their maximum WM span, and finally, they
participated in the delay tasks. The entire testing session lasted
between 2 and 3 hr.
Tests of emotional, cognitive, and
motor functioning were administered to the older adult subjects.
These included the Mini-Mental State Exam, the Beck Depression
Inventory, and the Digit Symbol—Coding subtest from the Wechs-
ler Adult Intelligence Scale—Third Edition (WAIS–III; Wechsler,
Immediate serial recall.
Subjects viewed letters presented on a
computer screen in a sequential manner. After seeing the initial
presentation of two letters, subjects were required to immediately
repeat aloud and in the same order the letters that they had just
read. This was conducted for two trials. If both trials were per-
formed correctly, then subjects were presented with two sequential
trials of three letters. This process continued with increasing num-
bers of letters until the subjects were unable to correctly repeat the
letters for either of the two trials. The number of letters for which
a subject could correctly repeat at least one trial was then defined
as the subject’s WM span and was used in the delay task.
Delayed recall and recognition.
task, subjects performed the delayed-response task. During this
task, they viewed letters presented sequentially on a computer
screen for 750 ms per letter (encoding period), followed by
a 6,500-ms delay period, and then were asked to indicate whether
they remembered the letters presented during the encoding period
During the encoding period, subjects were required to remember
either one letter (low load) or as many letters as was previously
defined as their WM span (high load). During the delay period,
subjects viewed either a simple fixation cross hair (distractor
absent) or a series of nine words presented at a rate of 333 ms per
word (distractor present). Subjects were instructed to view and pay
attention to the words but not to attempt to remember them,
because they would not be tested on them later. Words were
randomly selected from a list of 57 unique words and were
repeated randomly throughout the experiment. All words had one
syllable; contained three to five letters; were restricted to nouns,
After completing the span
AGING DEFICIT IN WORKING MEMORY WITH DISTRACTION
verbs, and adjectives; and were medium to high on the scale for
Brown verbal frequency, familiarity, concreteness, and meaning-
fulness (Coltheart, 1981). There were two types of response peri-
ods during the trials: recognition and recall. During half of the
trials, subjects viewed a single letter and indicated with a right
button press if the letter was a member of the set they had viewed
at encoding and with a left button press if it was not (recognition).
During the other half of the trials, subjects were required to state
aloud, and in the same order they had seen them, the letters they
had viewed at encoding (recall).
The combination of these conditions resulted in a 2 (load) ? 2
(distractor) ? 2 (response) ? 2 (age group) mixed analysis of
variance (ANOVA) design. The within-subject conditions were
counterbalanced in the following way: There were two blocks of
low load and two blocks of high load for each response condition
(recognition and recall). Each block contained 40 trials of delay
task. Blocks were presented in a set order, alternating between low
and high loads and beginning with low load. All four blocks for
one response condition were presented together, and the order of
response condition was counterbalanced across subjects. For ex-
ample, subjects would first complete 40 trials of the recognition
condition at low load, then 40 trials of the recognition at high load;
they then would perform another recognition low load block and
finally a recognition high load block before moving to the recall
condition. Half of the trials in each block had distractors during the
delay period, and half did not. The presentation of these trials was
varied randomly across the block. In total there were 320 delayed
and performance were automatically recorded for each subject’s
button press response. Performance was analyzed for hits, misses,
correct rejections, and false alarms. From these variables we
calculated accuracy (accuracy ? hits ? correct rejections/total
possible items), response bias, and discriminability. Response bias
is a subject’s propensity to respond “yes” or “no” in situations of
truly random noise and is calculated with the following formula:
response bias ? 0.5 ? [(z score of hits)2– (z score of false
alarms)2]. Discriminability is the measure of a subject’s ability to
correctly remember an item that had been previously viewed and
is uncontaminated by the subject’s response bias. Discriminability
is calculated with the following formula: (z score of hits) – (z score
of false alarms). Z scores were determined on the basis of the
normal distribution to avoid biases associated with the older or
younger group mean and standard deviation.
During the recall condition, subjects gave their re-
sponses verbally, and an experimenter recorded them. Later, these
responses were scored for accuracy. Because subjects had to repeat
each letter in the same order that they were presented during the
encoding period, this task was scored according to both lenient and
stringent criteria. For the stringent standard, each trial was scored
as either correct or incorrect. For the lenient standard, if subjects
repeated the letters from the encoding period in the order pre-
sented, they received 2 points. If they missed one letter or made
one transposition, they received 1 point. If they made more than
one mistake of either kind, they received 0 points.
During the recognition condition, response time
this investigation a power analysis was computed. We used Co-
hen’s (1988) calculations for power of an F test at ? ? .05 and u ?
3(2 ? 2 ? 2 ANOVA; Cohen, 1988). Given the preponderance of
evidence for a memory deficit in the elderly population (Folstein et
al., 1975), we estimated a large effect size for our analysis. At
predicted effect size of .40 and group N ? 26, power for our
analysis was .94. This was determined to be an acceptable level of
In accordance with the requirements of the journal,
for each significant comparison of interest, effect size was calcu-
lated. As a conservative measure of effect size Cohen’s d was
calculated for both independent and dependent comparisons on the
basis of the mean and standard deviation for each group (Cohen,
To determine the appropriate sample size for
Older adults exhibited a significantly lower mean WM span than
did younger subjects (older ? 4.82, younger ? 5.36; t ? 2.201,
p ? .033; d ? 0.7).
Because accuracy was calculated differently for the recognition
and recall conditions, analysis of the delay tasks was performed
independently for the recall and recognition tasks. Accuracy, dis-
criminability, response bias, and response time on the recognition
task and accuracy on the recall task were evaluated on the basis of
an Age (young, old) ? Load (span, single letter) ? Distractor
(present, absent) mixed ANOVA. Post hoc comparisons were
performed only for significant interactions, and significance was
set at p ? .05 for all results.
The recall trials were scored on the basis of both strict and
lenient criteria. When recall accuracy was scored according to the
lenient standard, all subjects performed less accurately at high
load, F(1, 50) ? 101.55, p ? .001, d ? 0.38, and no other effects
reached significance. Scoring recall accuracy according to the
strict standard (see Table 1 and Figure 1) revealed a main effect of
load, F(1, 50) ? 158.5, p ? .001, d ? 2.3, and a main effect of
distraction, F(1, 50) ? 8.45, p ? .005, d ? 0.10. Additionally,
there was a significant Load ? Distraction interaction such that
subjects were significantly less accurate when remembering mul-
tiple letters in the presence of distractors, F(1, 50) ? 9.814, p ?
.003, d ? 1.28. Neither scoring criteria revealed a significant main
effect or interaction with age.
Accuracy (see Table 1 and Figure 2A).
effect of load, such that all subjects were less accurate when
remembering multiple letters, F(1, 50) ? 22.7, p ? .001, d ? 0.75.
There was also a significant three-way interaction, Load ? Dis-
tractor ? Age, F(1, 50) ? 11.58, p ? .001, d ? 0.57. When
subjects performed the task at high load in the presence of dis-
There was a main
GAZZALEY, SHERIDAN, COONEY, AND D’ESPOSITO
tractors, older adults performed less accurately than did younger
adults. There were no other main effects or interaction effects with
age. In addition, there was no significant main effect of distraction
on accuracy, nor was there a Load ? Distraction interaction.
Discriminability (see Table 2).
older adults had significantly lower discriminability than did
younger adults under conditions of high load in the presence of
distractors, F(1, 50) ? 7.134, p ? .01, three-way interaction,
d ? 0.73. There was a main effect of load where all subjects had
significantly lower discriminability when remembering multiple
letters, F(1, 50) ? 21.57, p ? .001, d ? 0.64. Two additional
effects were significant when discriminability was examined.
There was a significant Load ? Distractor interaction, F(1,
50) ? 4.613, p ? .037, d ? 0.53, where all subjects showed a
greater effect of load in the presence of distraction. In addition,
older subjects showed greater decrement in performance than did
younger subjects in the presence of distractors, resulting in an
Age ? Distraction interaction, F(1, 50) ? 3.988, p ? .05,
d ? 0.17. There was no main effect of distraction on discrim-
As was found for accuracy,
with response bias as the dependent variable, no significant main
effects or interactions emerged. There was no main effect of age;
that is, older adults do not show a greater propensity to give
affirmative or negative responses.
Response time (see Table 3 and Figure 2B).
performed more slowly at high load relative to low load, F(1,
50) ? 47.622, p ? .001, d ? 0.99. There were no other main
effects or interactions for response time.
When recognition performance was analyzed
Digit Symbol—Coding Test
Older adults scored within the normal range for their age group
on the Digit Symbol—Coding test, 48.3 (SD ? 8.3), and this test
was not correlated with any dependent measures from the delay or
span tasks. The Digit Symbol—Coding test is used to evaluate
motor and perceptual processing speed, which have been revealed
to decline with age (Salthouse, 1992; Wielgos & Cunningham,
1999). It was used here to evaluate whether age-related changes in
processing speed correlated with the changes in memory measures.
In this study, age-related changes in WM performance on delay
tasks were evaluated at two memory loads, with and without
distraction during the retention period: a low load, consisting of a
single letter, and a high load equivalent to each subject’s prede-
termined digit span. The high memory load resulted in a decrease
in accuracy on the recall and recognition task in both younger and
older adults, consistent with increased difficulty in maintaining
multiple items. The presence of distraction during the delay period
resulted in a decrease in accuracy only in older subjects, and only
when they were maintaining high loads during the recognition
task, not the recall task. Thus, the principal aging finding of this
study was that older adults compared with younger adults exhibit
a significant impairment in accuracy on the delayed-recognition
task, but only during high memory load when maintenance was
interrupted with a distractor. The same finding of a three-way
interaction was observed for discriminability, but for the discrim-
inability measure it was also revealed that there was an Age ?
Distraction interaction, such that older subjects showed more of a
detrimental impact by distraction alone.
It is of interest that the current study revealed an age-related
WM deficit only in recognition performance and not for recall. It
Means and Standard Deviations in Accuracy (Percent Correct)
Younger subjectsOlder subjects
M SDM SDM SDM SD
scoring criteria. A Load ? Distractor ? Age analysis of variance reveals
only a main effect of load and distractor, such that there is a decrease in
recall accuracy at the higher load and with distractor but no age-related
effect. Error bars indicate standard error of the mean.
Bar graphs showing accuracy in the recall task for the strict
AGING DEFICIT IN WORKING MEMORY WITH DISTRACTION
may seem that this finding is disparate with studies that report an
age-related recall deficit out of proportion to an impairment in
recognition (Craik & McDowd, 1987; Erber, 1974; Gordon &
Craik, 1974; Perlmutter, 1979; Shonfield & Robertson, 1966).
However, previous studies used a very different experimental
design, testing superspan memory only after all material had been
presented, a more consolidated form of memory. Thus, the larger
recall deficit in older adults has been reported for episodic mem-
ory, not WM, and so different processes were being tapped from
those assessed in the current study. Studies that have used WM
delay tasks similar in design to the task used in our study have
documented recognition deficits with aging (Chao & Knight, 1997;
Nielsen-Bohlman & Knight, 1995), but they did not also assess
recall performance. Our finding of an age-related deficit in recog-
nition, with preserved recall performance in a WM delay task,
should lead us to question and further investigate the widely held
view that aging preferentially impacts recall.
Although recall performance at high load with distraction was
worse in both groups compared with recognition performance, it is
unlikely that the lack of an age-related difference during recall was
due to a floor effect. This is because recall performance in both age
groups was well above what would be expected by chance on a
recall task. The absence of an age-related deficit on the delayed
recall task, even in the presence of high load and distraction,
suggests that normal aging does not significantly affect WM main-
tenance/rehearsal processes. This leads one to question the mech-
anistic underpinnings of the selective recognition deficit.
The cognitive processes involved in recognition and recall are
clearly different and suggest that normal aging preferentially af-
fects cognitive processes engaged during the response period
(Rypma, Berger, Genova, Rebbechi, & D’Esposito, 2005).
Whereas recall on this task involved the “reading out” of items
represented in WM (Kieras, Meyer, Mueller, & Seymour, 1999),
recognition required at least two operations not required by the
recall task: comparison of the probe against items represented in
WM and a decision about how to interpret and act on the outcome
of this comparison (Ratcliff, 1978; Sternberg, 1969). Our findings
suggest that these recognition processes are differentially affected
by aging and result in a performance deficit when the WM main-
tenance system is stressed under the presence of high load and
Distractor ? Age analysis of variance reveals a main effect of load, such that there is a decrease in accuracy at
the higher load. Analysis also revealed an Age ? Load ? Distractor interaction (*p ? .05), such that there is
an age-related decrease in accuracy only at the higher load in the presence of distraction. (B) For response time,
a Load ? Distractor ? Age analysis of variance reveals only a main effect of load, such that there is an increase
in response time at the higher load but no age-related effect. Error bars indicate standard error of the mean.
Bar graphs showing accuracy and response time in the recognition task. (A) For accuracy, a Load ?
Means and Standard Deviations in Discriminability on the
Younger subjectsOlder subjects
M SDM SD
Means and Standard Deviations in Response Time (in
Milliseconds) on the Recognition Task
Younger subjects Older subjects
M SDM SD
GAZZALEY, SHERIDAN, COONEY, AND D’ESPOSITO
distraction. Signal detection methodology revealed that the recog-
nition deficit was not the consequence of a more liberal response
bias with aging but an impairment in the ability of older subjects
to discriminate between old and new stimuli.
Given reports that a deficit in preventing distracting information
from interfering with WM stores is associated with normal aging
(Chao & Knight, 1997; Gazzaley et al., 2005; Hasher & Zacks,
1988; West, 1999), it is possible that an age-related deficit in
inhibitory control contributes to the recognition performance def-
icits observed in this study. This inhibitory deficit may result in the
older subjects’ inadequately ignoring the distracting information
presented during the delay period, thus leading to interference with
maintaining relevant information (Gazzaley et al., 2005). Addi-
tionally, an inhibitory deficit may have expressed itself as proac-
tive interference from previously presented letters (Bowles &
Salthouse, 2003; Lustig, May, & Hasher, 2001), which may in turn
be accounted for by a deficit in monitoring the source of informa-
tion in WM (Hedden & Park, 2001; Henkel, Johnson, & De
Leonardis, 1998; Mitchell, Raye, Johnson, & Greene, 2006). A
source memory deficit would be consistent with our finding that an
age-related deficit in the delayed recognition task occurs only
under conditions of high load and distraction. It is during these
conditions that subjects would have the greatest difficulty in track-
ing the source of the information, thus resulting in the most
proactive interference and the worst recognition performance. Fur-
thermore, this mechanism is consistent with a selective recognition
impairment that is induced by confusion in distinguishing probes
from previously presented cues during recognition trials, a source
of confusion that is not present during the recall trials when the
subjects must actively generate a representation of the item.
A search for a parsimonious neural explanation for how an
interaction of distraction and memory load results in impaired WM
recognition performance suggests the possibility of an age-related
deficit in prefrontal cortical function. The prefrontal cortex has a
well-established role in the protection of memories held in WM
from distraction (Chao & Knight, 1995; Miller, Erickson, & Desi-
mone, 1996; Sakai, Rowe, & Passingham, 2002), and increasing
memory load leads to increased activity within the prefrontal
cortex during WM recognition tasks (Braver et al., 1997; Druzgal
& D’Esposito, 2001, 2003). Furthermore, an event-related poten-
tial experiment by Chao and Knight (1997) revealed that distrac-
tor-induced recognition accuracy deficits in older subjects was
accompanied by reduced attention-related activity over frontal
regions (Chao & Knight, 1997), and fMRI studies revealed a
reduced ability of older adults to increase prefrontal cortex activity
in response to increasing load relative to young adults (Mattay et
al., 2006; Rypma, Prabhakaran, Desmond, & Gabrieli, 2001).
Lastly, it has recently been revealed that age-related deficits in
source monitoring may also be associated with neural changes in
the prefrontal cortex (Mitchell et al., 2006). Thus, impairments in
prefrontal cortical function, as proposed by the frontal hypothesis
of aging (West, 1996, 2000), may represent an underlying etiology
for WM performance deficits observed in this study. This does not
imply that prefrontal cortical deficits are the only alteration that
occurs with aging, rather that it may represent a unifying expla-
nation for the observed interactions in this study.
Another interpretation to consider is that these findings may
reflect a generalized slowing of information processing in older
adults. This theory of cognitive aging promoted by Salthouse
(1996, 2000) proposes that an age-related decline in processing
speed results in deficits that cross a broad range of cognitive
domains. We suspect that this is unlikely because of the specificity
of age-related findings to one behavioral condition and the fact that
no difference was observed in response time associated with that
condition. Additionally, there was no correlation in the older
subjects between recognition performance and a measure of pro-
cessing speed (i.e., the Digit Symbol—Coding test).
Although not the primary focus of this study, the memory span
analysis revealed that older adults exhibit a small but significantly
reduced forward letter span compared with that of younger adults
(older ? 4.82, younger ? 5.36). Simple span tests—when assessed
with the immediate serial recall of letters, digits, words, or
shapes—are thought to be a reflection of a storage system, or
purely mnemonic portion of WM, as described by Baddeley
(1986). There have been mixed results regarding the presence of
age-related span deficits in other studies (Dobbs & Rule, 1989;
Light & Anderson, 1985; Wingfield et al., 1988). One possible
reason for such a discrepancy is the variability in the type of tasks
used and the potential impact of subtle differences in design. For
example, Wingfield et al. (1988) found no age-related difference
on forward digit span; however, they used a verbal presentation of
digits in contrast to the written presentation of letters used in our
study. This discrepancy in findings may represent a difference in
letter versus digit WM or an age-related difference in reading
versus verbal processing efficiency rather than storage capacity. It
is also important to acknowledge that the aging process contributes
a great deal of performance variability, which can be reflected as
differences in studies even with modestly large study populations.
To address these confounds, a recent study involving 1,183 sub-
jects whose ages ranged across the entire life span examined WM
span with 11 different multimodal digit span tasks involving
combinations of different input/output options (e.g., hearing and
reading / writing and speaking; Karakas, Yalin, Irak, & Erzengin,
2002). Karakas et al. (2002) found that all measures of forward
digit span, when controlled by education level, decreased across
the life span after peaking at 18 years of age.
Our results and those of Karakas et al. (2002) suggest a decrease
in WM storage capacity with aging. An alternative interpretation
of this finding is that it does not represent a decrease in storage
capacity per se but rather increased proactive interference in aging,
as was hypothesized as one of the potential etiologies of the
delayed recognition deficit. When reading span was tested in a
manner to minimize proactive interference, span in older individ-
uals increased (Lustig et al., 2001; May, Hasher, & Kane, 1999).
Subjects in the present study performed a forward letter span task
with items repeated across trials, which generates increasing pro-
active interference with each subsequent trial secondary to the
presentation of items on the multiple preceding tests (May et al.,
1999). Thus, differences in span may correspond to differences in
the ability to suppress interference from competing items from
previous trials and therefore may be a reflection of inhibitory
deficits in aging.
In summary, this study revealed age-related impairments in WM
recognition performance only for the combination of high memory
load and distraction. These results suggest that recognition pro-
cesses are differentially vulnerable to aging effects and result in a
performance deficit when WM maintenance systems are taxed by
the presence of high load and distraction. It is important to note
AGING DEFICIT IN WORKING MEMORY WITH DISTRACTION
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Received April 17, 2006
Revision received April 18, 2007
Accepted April 23, 2007 ?
Call for Nominations
The Publications and Communications (P&C) Board of the American Psychological Association
has opened nominations for the editorships of Psychological Assessment, Journal of Family
Psychology, Journal of Experimental Psychology: Animal Behavior Processes, and Journal of
Personality and Social Psychology: Personality Processes and Individual Differences (PPID),
for the years 2010-2015. Milton E. Strauss, PhD, Anne E. Kazak, PhD, Nicholas Mackintosh, PhD,
and Charles S. Carver, PhD, respectively, are the incumbent editors.
Candidates should be members of APA and should be available to start receiving manuscripts in
early 2009 to prepare for issues published in 2010. Please note that the P&C Board encourages
participation by members of underrepresented groups in the publication process and would partic-
ularly welcome such nominees. Self-nominations are also encouraged.
Search chairs have been appointed as follows:
Psychological Assessment, William C. Howell, PhD, and J Gilbert Benedict, PhD
Journal of Family Psychology, Lillian Comas-Diaz, PhD, and Robert G. Frank, PhD
Journal of Experimental Psychology: Animal Behavior Processes, Peter A. Ornstein,
PhD, and Linda Porrino, PhD
Journal of Personality and Social Psychology: PPID, David C. Funder, PhD, and Leah
L. Light, PhD
Candidates should be nominated by accessing APA’s EditorQuest site on the Web. Using your
Web browser, go to http://editorquest.apa.org. On the Home menu on the left, find “Guests.” Next,
click on the link “Submit a Nomination,” enter your nominee’s information, and click “Submit.”
Prepared statements of one page or less in support of a nominee can also be submitted by e-mail
to Emnet Tesfaye, P&C Board Search Liaison, at email@example.com.
Deadline for accepting nominations is January 10, 2008, when reviews will begin.
AGING DEFICIT IN WORKING MEMORY WITH DISTRACTION