Download Working Memory and Older Adults

Working Memory and
Older Adults:
Implications for
Occupational Therapy
Corinna Andiel, Lili Liu
Key words: aging. Alzheimer's disease
Atkinson and Shijfrin 's (1968) modal model 0/ memmy is still commonlv used by rehahilitation professionals to evaluate memory impairment in older
adults. However, research to date has heen unahle to
indicate that short-term memor)' declines with age.
These findings haue led some rehabilitation professionals to mistakenzy conclude that short-term memmy is not affected by the aging process. This article reviews both the traditional concept of short-term
memory, as outlined hy Atkinson and Shljfrin. and the
more recent conceptualization of short-term memory
in terms of Baddeley and Hitch's (1974) model of
working mem01)' The implications 0/ the concept 0/
working memory has implications for occupational
therapy interventions for older adults. For example,
clients with dementia may experience difficulties in
pel/arming tasks that require drawing inferences.
Similarly, language that contains vague references
may present problems for these clients. In addition,
changes in working memory in older adults suggest
that they may experience diffiCUlties with medication
management and whal Rule, k/i/ke, and Dobhs (1992)
called wayfinding. Therefore, evaluations of working
memory would provide a beller indication 0/ older
adults' memory performance than the modal model.
Corinna Andiel, MA. is a doctorate student in Rehabilitation
Science, 2-64 Corbett Hall. Department of Occupational Therapy, Faculty of Rehabilitation Medicine, University of Albena,
Edmonton, Alberta, Canada, T6G 2G4.
Lili Liu, PhD. is Assistant Professor, Depanment of Occupational Therapy, Faculty of Rehabilitation Medicine, University of
AJberta, Edmonton, Albena, Canada
Tbis arlicle was accejJted/or pub/lcatlo'" September 15, 1994.
ognitjve psychologists' conceptualization of shonterm memory has undergone significant
changes in the past twO decades. Currently,
shon-term memory tasks are commonly thought of as a
continuum, with involvement of primaly memory on one
end and working memory on the other (Craik, Anderson,
Kerr, & Li, in press). Although shon-term memory is
commonly evaluated in older adults, research has indicated that there is little change in this type of memory with
age (Craik & Jennings, 1992). On the other hand, a substantial body of evidence has indicated that older adults
display decrements in working memory (Hultsch, Hertzog, Small, & McDonald-Miszczak, 1992; Morris, 1986;
Saithouse, 1992). Nevertheless, a review of the occupational therapy literature revealedlitt\e discussion of working memory and how or why it should be evaluated. The
purpose of this article is to present a brief overview of
short-term memory and working memory and the implications for memory evaluation in older adults.
C
Modal Model of Memory
In the occupational therapy literature on aging, memory
is discussed in terms of a distinction between recall of
events from the immediate past and recall of events from
the distant past (Hansen & Atchison, 1993; Pedretti,
1985). Such references to memory reflect Atkinson and
Shiffrin's (1968) modal model of memory (see Figure 1)
There are three structural components of memory in this
model: the sensory register, short-term store, and 10ngterm store. The sensory register is where an incoming
stimulus is immediately registered in a form that is consistent with the sense modality of the stimulus (e,g., visually,
auditorily). From the sensory register, information is
transferred to the short-term store, which will be discussed in more detail Finally, information is transferred
From the short-term to the long-term store, where inFormation storage is relatively permanent and the capacity
for holding information is relatively large.
In contrast to long-term store, short-term store is
assumed to have a much more limited capacity. It is the
site of temporary memory processes, such as subvocal
rehearsal or a mnemonic that is used when a list of items
is to be memorized. It is believed by Atkinson and Shiffrin
(1968) that the capacity of the short-term store is reHected in one's performance on immediate memory span
tasks, such as the digit span task. In the digit span task, a
person is presented with a series of digits and then is
asked to repeat the sequence of digits he or she just
heard (Baddeley, 1989). The number of digits an individual recalls in the correct order reRects the short-term
store capacity (Morris & Baddeley, 1988).
In their model, Atkinson and Shiffrin (1968) assumed that an item must pass through the short-term
store before it can enter the long-term store. They also
assumed that the longer the item is held in the short-term
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681
Incoming
Stimulus
--.
SENSORY REGISTER
SHORT-TERM
STORE
LONG-TERM
STORE
(e.g. visual, auditory)
(Includes temporary
processes such as
rehearsal)
(e.g. visual, auditory)
Figure 1. Schematic representation of the modal model of memory.
store, the greater the learning involving the item that will
occur. However, the results of several studies question
the assumptions of the modal model. For example, Craik
and Watkins (1973) failed to find a positive correlation
between the amount of time an item is held in short-term
memory and the amount of long-term learning that has
occurred. Moreover, patients with brain damage and severely impaired short-term memory have exhibited longterm learning (Baddeley, 1989).
Working Memory
Because of the problems the above research poses for the
modal model, several alternative models of memory have
been proposed. Since the 1970s, the concept of shortterm memory has evolved into a continuum of memory,
with primary memory at one end and working memory at
the other. Primary memory is based on the more traditional notion of short-term memory as a unitary system
involving the temporary storage of information (Morris &
Baddeley, 1988; Salthouse, 1990). Its capacity is reflected
in the amount of information that can be held in conscious awareness (Craik et aI., in press). Primary memory
is assessed by using tasks that require only passive storage of information, that is, tasks in which information is
given to a person who is then required to repeat the
information immediately. Thus, the information is given
back in the same form it was presented, as in the digit
span task (Craik et aI., in press). Interestingly, research
results have suggested that older adults display little performance decrement in primary memory tasks (Craik &
Jennings, 1992). Despite this finding, memory span tasks
are often used in assessments of memory of older adults.
However, working memory tasks are seldom included.
Like primary memory, working memory is presumed to have a limited capacity (Salthouse, 1990). However, working memory is distinguished from primary
memory by it~ simultaneous involvement in storing and
processing information (Daneman & Tardif, 1987; Light,
1991; Salthouse, 1990; Salthouse, Babcock, & Shaw,
1991). Working memory function is exemplified in a mental arithmetic task in which two-digit numbers are multi-
682
plied without the aid of pen and paper. In this task a
person is required to do the computations mentally, store
the results of the computations, and coordinate between
the storage and processing of that information to arrive at
the answer (Salthouse, 1991).
Much of the research on working memory has been
conducted within the context of Baddeley and Hitch's
(1974) three-component model, the Working Memory
Model (see Figure 2). The model includes a processing
component called the Central Executive System, along
with twO of what Baddeley and Hitch called slave systems,
the visuospatial scratch pad and the articulatory loop. The
latter two systems are part of the working memory's storage component and are responsible for the temporary
storage of visuospatial information and speech-based information, respectively (Baddeley, 1989). The Central Executive System is responsible for selecting and controlling
processing of information (Light, 1991); because working memory is assumed to have a limited capacity, its
allocation between the processing and storage components varies according to the demands of the task (see
Figure 2).
The implications of this more recent conceptualization of short-term memory as including not only primary
memory but also working memory are particularly noteworthy for the evaluation of older adults' memory functioning. In general, the research to date has indicated
that, for a memory task, differences between older and
younger adults increase with the demands of working
memory (as opposed to primary memory) (Craik et aI., in
press; Craik & Jennings, 1992; Morris, Gick, & Craik,
1988). This pattern is even more pronounced when older
adults with Alzheimer's disease are considered (Becker,
1988; Morris & Baddeley, 1988; Spinnler, della Sala, Bandera, & Baddeley, 1988).
The influence of working memory demands on older
adults' task performance is illustrated by Dobbs and
Rule's (1989) findings. In their study, 228 adults in 5 age
groups (30-39 years, 40-49 years, 50-59 years, 60-69
years, and 70 years and older) were given a variant of a
working memory task outlined by Kirchner (1958). Participants were presented a series of digits auditorily. In
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Central Executive
Systems (CES)
Slave Systems:
(Processing Component)
..
CES
(Processing
- visuo-spatial
scratchpad
- articulatory
loop
(Storage Component)
As demands made by the storage component increase,
allocation of working memory to the processing
component decreases.
SLAVE SYSTEMS
(Storage Component)
Component)
Figure 2. Schematic representation of working memory.
the Lag 0 (control) condition, a participant repeated each
digit out loud immediately after it was presented. In the
Lag 1 condition, a participant repeated the digit heard
before the one just presented. In the Lag 2 condition, a
participant repeated the digit heard before the two digits
just presented. In the Lag 1 condition there was minimal
emphasis on storage, but some demands were made 0"
processing. In the Lag 2 condition, there was a slight
increase in the storage component with an increased emphasis on the processing component. When the authors
examined the numher of correct responses produced before the first error, there were no age differences in performance ar Lag O. However, participants in the 60-69
years and 70 years and older age grou ps performed significantly more poorly than did the younger groups in
both Lag 1 and Lag 2 conditions, and they performed
significantly more poorly in the Lag 2 condition than in
the Lag 1 condition. These results support the hypothesis
that older adults have more difficulty performing a task as
the demand on working memory increases.
Working memory may also deteriorate in age-related
pathologies. Baddeley (1992) and Morris and Baddeley
(1988) have provided evidence to indicate thar Alzheimer's disease selectively involves the Central Executive System. These researchers have shown that with the
progression of Alzheimer's disease, performance on specific phonological tasks remains intact, whereas performance on combined tasks deteriorates when compared
[0 that of young and old control subjects without Alzheimer's disease.
Implications for Occupational Therapy
Given the findings suggesting that older adults demon-
strate difficulty in working memory tasks, but not in primary memory tasks, the question that inevitably arises is
how these findings translate into perfol;'dnce of daily life
tasks. The research discussed thus far suggests that tasks
involving passive reproduction of inFormation should be
spared. For example, older adults should demonstrate
little, if any, difficulty in looking up and dialing telephone
numbers (Craik et aI., in press).
Intact working memory is required when a person
draws inferences in order to comprehend complex text or
discourse (Campbell & Charness, 1990; Salthouse, 1990).
Drawing inferences is especially problematic for older
adults who have Alzheimer's disease (Craik & Jennings,
1992). Consequently, clients with dementia may experience difficulties when they perform tasks that require
inference. For example, Kortman (1992) found that the
success of splint treatments depends on a client's ability
to recall and understand the regimen. Therefore, he recommended that short sentences be used when therapists
provide written instructions.
Literal language minimizes the amount of inference
required by a client with Alzheimer's disease. For example, "Sit down" may be easier For the client to understand
than "Take a seat." Vague rderences sucn as "it," "he" or
"she," and "over there" should be aVOided, and sentences
should he simple without being condescending.
Impaired working memory affects medication management. Deficits in working memory may make it difficult For older adults to follow instructions and plan their
medication schedules. For example, Kendrick and Bayne
(1982) found that some clients did not take their medications because they misinterpreted the instructions, and
Anderson (1993) reported that a group of older adults
was able to interpret medication instructions for intake if
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683
the instrucrions required minimal inference Const:4uent]y, Anderson (1993) argued that, to compensate for
older adults' decline in working memory, caregivers
should monitor the pace and amount of information ren-
Salthouse, 1990; Foos, 1989; Salthouse, 1990). Second,
researchers (Daneman & Tardif, 1987; Morris et aI., 1988
Salthouse, 1990; Salthouse, 1991) have disagreed on
whether working memory should be thought of as a do-
dered. That is, older adults display better understanding
main specific or general purpose system. For example, is
of medications when they are given specific information
in small amounts.
Researchers have also suggested that deficits in
working memory may be at least partially responsible for
older adults' problems with what Rule, Milke, and Dobbs
(1992) called wayfinding, because this activity is assumed to involve continual storage and processing of
information (Aubrey & Dobbs, 1989; Kirasic, 1991; Kirasic, Allen, & Haggerty, 1992). Moreover, wayfinding may
be especially difficult for older adults when they are in
unfamiliar environments (Kirasic, 1991). Similarly, Liu,
Gauthier, and Gauthier (1991) found that when persons
in the early stages of Alzheimer's disease are asked to find
their way in new environments and in familiar ones, they
are impaired in the new environments, but not in the
familiar environments. In terms of Baddeley and Hitch's
(1974) model of working memory, more demands are
placed on the slave system of tile storage component of
working memory (specifically, the visuospatial scrarehpad) when a person is in an unfamiliar environment.
Because of the additional load that is placed on the storage component, less of the limited working memory capacity is available for the Central Executive System's processing component, which is reqUired for organizing and
integrating spatial information in wayfinding (Kirasic et
aI., 1992; Kirasic & Bernicki, 1990). This hypothesis suggests that wayfinding abilities of older adults may be improved by familiarizing them with an environment over a
period of time so that demands on the storage component of working memory will be minimized. Alzheimer's
disease may affect the ability to process information despite an intact ability to store visual or verbal information.
Alternatively, it is possible that Alzheimer's disease affects
both the slave systems and the Central Executive Systems.
there one working memory system for reading and a
separate system for mathematics, or is there is a general
working memory processor that is used for both tasks?
As a consequence of these issues, it is difficult to set
strict guidelines for selecting an appropriate assessment
instrument. Nevertheless, some general recommendations have been proposed. Some tasks are designed to tax
the storage component of working memory, whereas
others manipulate the processing component and still
others the coordination between these two components.
Therefore, occupational therapy practitioners are advised
to evaluate working memory with a few instruments that
test each of these components rather than relying on a
single, global instrument (Craik et aI., in press). For example, one type of working memory instrument was described in the Dobbs and Rule (1989) study discussed
earlier. The emphasis of thiS lag task on the active manipulation of information with minimal storage demands
suggests that it is a measure of the processing componem
of working memory. Clinicians may find the working
memory task outlined by Dobbs and Rule (1989) useful
because it is sensitive to aging and is easy to administer
(Craik et ai., in press). In addition, Salthouse (1990) provided a list of 10 working memory tasks that involve the
simultaneous processing and storage of information. An
example is the alphabet sran task, in which participants
are required to repeat out loud a series of words after
arranging them in alphabetical order. The rearranging of
the words alphabetically draws on the processing component of working memory; the storage component consists of holding in memory the list of words that were
presented.
Most research on working memory has been conducted with auditory stimuli, thereby examining the articulatory loop of working memory. Less is known about
the visuospatial scratchpad, which provides temporary
storage and maintenance of visuospatial rather than verbal material (Farmer, Berman, & Fletcher, 1986; Morris &
Baddeley, 1988). Occupational therapists who evaluate
older adults' working memory function in daily activities
are advised also to consider visuospatial stimuli. Results
from research that use visuospatial stimuli suggest that
working memory is task specific. For example, ClarksonSmith and Hartley (1990) found that bridge players between the ages of 55 and 91 years perform better on
working memory tasks than persons who do not play
bridge. An alternative explanation is that playing bridge
has delayed the decline of working memory that accompanies aging (Clarkson-Smith & Hartley, 1990).
Currently, occupational therapists use standardized
assessments to determine cognitive performance of c1i-
Clinical Evaluation of Working Memory
Given the abundance of research indicating that working
memory declines with age and therefore disrupts performance on a variety of tasks, the next question that
arises for occupational therapists is how to evaluate working memory in the clinic. To date, there is no clear consensus on this issue for two reasons. First, researchers
have disagreed on what component of working memory
is responsible for age differences (Salthouse, 1991).
Working memory is postulated to involve storage of information, processing of information, and coordination be
tween siorage and processing of the information; each of
these factOl's has been proposed as a source of age differences in working memory task performance (Babcock &
684
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ents. Examples of these are the Kitchen Task Assessment
(Baum & Edwards, 1993) and the Allen Cognitive Level
test (Allen, 1991). As these assessmentS do not address
working memory, other standardized functional assessments that examine working memory need to be
developed.
Conclusion
Some occupational therapy clinicians and rese3rchers
(e.g., Zoltan, 1990) may consider shon-term memory in
terms of Atkinson and Shiffrin's (1968) model- as a passive, temporary storage system. When applied to the evaluation of older adults, this model may lead to the conclusion that shon-term memory is not affected by age. One
of the many tasks occupational therapists are required to
perform is an evaluation of a client's ability to perform
daily life tasks. These evaluations should go beyond determining a client's level of independence to determine
why he or she may be experiencing difficulty (Robinson,
1992). We propose that a closer examination of working
memory will not only enhance occupational therapy evaluation but also provide a better indication of what interventions are needed .•
References
Allen, C. (1991). Allen Cognitive Level (ACL) Test ln Msessing adults: Functional measures and successful outcome
(Section I). Rockville, MD: American Occupational Therapy
Association.
Anderson, M. (1993). Age dif/erences in prescription
scheduling and recall as influenced hy schema development.
Unpublished doctoral dissertation, Universiry of Alberta.
Edmonton.
Atkinson, R., & Shiffrin, R. (1968). Human memory: A proposed system and its control processes. In K W Spence &] T
Spence (Eds.), The psychology of learning and rnotiuation.
Advances in research and theory (Vol 2) (Pp 89-195). New
York: Academic.
Aubrey,]., & Dobbs, A. (1989). Age differences in extrarersonal orientation as measured by performance on the locomotor maze. Canadian journal on Aging, 8, 333-342
Babcock, R, & Salthouse, 1'. (1990). Effects of increased
processing demands on age differences in working memory
PsychOlOgy and Aging, 5, 421-428
Baddeley, A. (1989). The uses of working memory In P
Soloman, C Kelley, G. Goethals, & B. Sterhens (Eds.), iYlemoly
Interdisciplinary appmaches CPr. 107-123). New York: SpringerVerlag.
Baddeley, A. (1992). Working memory Science, 225,
556-559
Baddeley, A., & Hitch, G. (1974) Working memolY In G A
Bower (Ed.), The psychology of learning and rno/ivation (Vol
8). New York: Academic.
Baum, C, & Edwards, D. (1993). Cognitive performance in
senile dementia of lhe Alzheimer's lype: The Kilchen Task As·
sessment. American journal of Occupational Therapv, 47.
431-436.
.
Becker,]. (1988). Working memory and secondarv memory deficits in Alzheimer's Disease. journal of Clinical and
Fxperimental
Neurop~ycholof!,y,
]0, 739-753.
Camphell,] ,& Charness, N. (1990). Age-related declines in
working memory skills: Evidence from a complex calculation
task. Developmental Psycholog)/, 26, 879-888.
Clarkson-Smith. L., & Hartley, A. A (1990). The game of
hridge as an exercise in working memory and reasoning. journal 0/ Gerontology Psvchological Sciences, 45, P233-238.
Craik, F., Anderson, N. Kerr, S, & Li, Z. (in press) Memory
changes in normal ageing. Tn A. D. Baddeley, B. A. Wilson, & F.
Watts (Eds). Handbook ofmernory disorders. Chichester, England: Wiley.
Craik, F., &Jennings,j. (1992) Hum3n memory In F. Craik
& T Salthouse (Eds.), Handbook of aging and cognition
(pp. 51-110) Hillsdale, N] Erlbaum.
Craik, F., & Watkins, M. (1973) The role of rehearsing in
short-term memory. journal 0/ Verbal Learning and Verbal
Behaviour, ]2, ')99-607
Daneman, M., & Tardif, T (1987). Working memory and
reading skill re-examined. In M. Colt heart (Ed.), Allen/ion and
PeJjormance XlI The psychology of reading (pp. 491-508).
East Sussex, England: Erlhaum.
Dobbs, A., & Rule, B G (1989). Adult age differences in
working memory. Psychology and Aging, 4, 500-503.
Farmer, E. W, Berman, ]. V F., & Fletcher, Y L. (1986).
Evidence for a visuo-sratial scratch-pad in working memory.
Quarterlv journal of E,perimental Psychology, 38A, 675-688
Foos, P (1989). Adult age differences in working memory.
Psychology and Aging 4, 269-275
Hansen, R, & Atchison, B. (1993). Thinking like an OT In
R. Hansen & B. Atchison (Eds.), Conditions in occupational
therapy Effect on occupational performance (pp. 1-15). Ballimore Williams & Wilkins.
Hullsch. D, Hertzog, C, Small, B, & McDonald·Miszczak.
L. (1992). Short-term longitLIdinal change in cognilive performance in later life Psychology and Aging. 7, 571-584
Kendrick, R., & Bayne, J (1982). Comrliance and [)fe·
scribed medication by elderly ralients Canadian Medical MSOcia/ion./ournal, ]27, 961-962.
Kirasic, K. (1991). Spatial cognition and hehavior in young
and elderly adults: Implications for lear'ning new environments.
Psychology and I\.ging 6, 10-18
KinlSic. K. Allen. G., & Haggerty, D (1992). Age-related
differences in adults' macrospatial cognitive rrocesscs. Fxperi-
rnen/al /\gin!? Research, 18, 33-39
Kirasic, K, & Bernicki, M. (1990). Acquisition of sratial
knowledge under conditions of temperospatial discontinuity in
young and elderly adulls. Psychological Research, 52, 76-69.
Kirchner. W (19')8) Age diffel'ences in short-term relenlion of rapidly changing informalion.journal o/E>;:perimental
Psycholopy, 55, 352-358
Korrman, B (1992) Patient recall and understanding of
inslruuions concerning splints follOWing a zone 2 flexor lendon
rerair Australian Occupational Therapv./ournal. 39, 5-11.
Light. I.. (1991). MemolY and aging Four hypotheses in
search of dala. Annual Reuiew of PSl'cboloRl'. 42, 333-376.
Liu, L, Gaulhier, L.. & Gauthier, S. (1991) Spatial disorienlation in rersons Wilh early senile demenlia of lhe Alzheimer
tyre. American journal of Occupational Therapy, 45, 67-74.
Morris, R (1986). Working memory 1974-19iJ4 A review
of a decade of research. CurTent Psycholo!?ical Research and
Reuie/us. 5. 2iJl-29'i.
Morris, R. & Baclcleley, A. (198iJ) Primal)' and working
memory funCtioning in Alzheimer-lyre clementia joul71a1 of
Clinical and Etperimental Neuropsl'chology.
f().
279-296.
Morris, R., Gick, M. & Craik, F. (1988). Processing resources ancl age c1iffel'Cnces in working memory. iV/emory 'and
Cognition. !o, 562--\66
The American joumal o/OcCilpational Thempl'
Downloaded From: http://ajot.aota.org/pdfaccess.ashx?url=/data/journals/ajot/930172/ on 05/05/2017 Terms of Use: http://AOTA.org/terms
685
Pedn:rti, L (198'5) Evaluation of sensation, perception and
cognition. In I.. Pedretti (Ed.), Occupational therapy Practice
skills for physical dysfunction (pp. 99-111). Sr. Louis: Moshy.
Robinson, S (1992). Occupational therapy in a memory
clinic British Journal of Occupational Therapy, 55, 394-396
Rule, B. G, Milke, D. 1.., & Dohhs, A. R (1992). Design of
institutions: Cognitive functioning and social interactions of the
aged resirlent.j()urnal ofApplied Gerontology, I I (4), 47'5--488.
Sa!thouse, T (1990). Working memory as a processing rcSOUITe in cognitive aging. Developmental Review, 10, 101-124
Salthouse, T (1991). Reduced processing resources. In
Theoretical perspectives on cognilive aging (pp. 301-349).
686
Hillsdale, NJ: Lawrence Erlhaum.
Salt house, T (1992). Why do adult age rlifferences increase
with task complexity? Developmental Psychology, 28, 905-918.
Sa]thousc, T, Bahcock, R, & Shaw, R. (1991). Effects of age
on structural and operational capacities in working memory.
PS)lchology and Aging, 6, 118-127.
Spinnlcr, H., della Sala, S., Bandera, R, & Baddeley, A.
(1988). Dementia, ageing, and the structure of human memory.
Cognitive Neuropsychology, 5, 193-211.
Zoltan, B. (1990). Evaluation and treatment of cognitive
dysfunction. In Occupational therapy: Practice skills for physical dysfunction (pp. 202-207). Sr. Louis: Moshy.
julF/August 1995, Volume 49. Number 7
Downloaded From: http://ajot.aota.org/pdfaccess.ashx?url=/data/journals/ajot/930172/ on 05/05/2017 Terms of Use: http://AOTA.org/terms