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Kayla Duperreault
Sarah Ryan
CO300
March 26, 2010
The Influence of Long-Term Representations on Refreshing Information in Working Memory
Abstract
Working memory is an on-line cognitive system that controls our ability to concurrently
maintain and process information. Using simple span and complex span tasks, the functions of
working memory can be directly observed and measured.
Results from McCabe (2008)
demonstrated that immediately recalling items from a simple span task (word span) is much
easier than doing so from a complex span task (operation span), however an opposite effect is
observed at delayed recall. Specifically, participants showed an increase in performance when
recalling items after a delay for words that were studied during the operation span task, than
those from the word span task. Based on Cowan’s embedded-process model (1999), McCabe
(2008) developed the covert retrieval model to explain this delayed recall effect. According to
this model, the processing component of the complex span task gives participants an opportunity
to attentionally refresh and brings items back into the focus the attention from the activated
portion of long-term memory. It has been proven that we hierarchically process items with
different depths or levels, starting with shallow processing for phonological characteristics, such
as what the word sounds like, and then accessing deep levels of processing for the semantic
characteristics, or the meaning of the word. Items, such as non-words, are lacking long-term
semantic networks and, therefore, only have access to phonological characteristics. The purpose
of this research is to replicate the delayed recall effect findings from McCabe (2008) and to
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examine if it is possible to attentionally refresh items that are lacking pre-existing semantic
networks. It is predicted that it will be more difficult to retrieve non-words than words because,
without long-term networks, non-words will not be as readily available in the activated portion
of long-term memory.
What is Working Memory and how do we examine it?
Working memory, as originally proposed by Baddeley and Hitch in 1974, is a multi-store
cognitive system responsible for the simultaneous temporary storage and manipulation of
information (Miyake & Shah, 1999). According to the multi-component model of working
memory, the central executive is the attentional control component responsible for coordination
of the two subsidiary memory systems, the phonological loop and the visuospatial sketchpad
(Baddeley & Logie, 1999). An additional function of the central executive is the act of
refreshing, or briefly reactivating previously attended items back into the focus of attention
(Cowan, 1993). Given that working memory is accountable for both processing and storage,
working memory tasks are designed to directly test these functions (Daneman & Carpenter,
1980). Simple span tasks typically involve consecutive presentation of the to-be-remembered
items for, usually, one-second each, subsequently followed by recall test. Complex span tasks
are roughly identically to simple span tasks, except a processing component is presented prior to
each to-be-remembered item. Simple span trials with short list-lengths allow items to be recalled
directly from primary memory, so items are briefly stored and then recalled (Unsworth & Engle,
2006). Alternatively, the processing component of complex span tasks causes items to be
displaced out of the focus of attention and retrieved from secondary memory instead (McCabe,
2008; Unsworth & Engle, 2006). Because complex span tasks tax both the maintenance and
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processing functions of working memory, they are thought to more related to higher-order
cognition than simple span tasks (Unsworth & Engle, 2007).
The Delayed Recall Effect and the Role of the Covert Retrieval Model
The delayed recall effect, as tested in McCabe (2008), compares retrieval rates for words
processed during simple span tasks and complex span tasks. Subjects completed trials of two,
three, and four to-be-remembered words using both word span and operation span tasks. Items
processed with the simple span task showed higher rates of retrieval during immediate recall than
those processed with complex span task. A converse effect resulted after a delay in which there
was a greater recall for words processed during the operation span task than the word span task
(McCabe, 2008). This increase in performance for complex span task at delay was also directly
related to the number of covert retrieval opportunities that was given during the operation span
task. McCabe (2008) proposed the covert retrieval model as the explanation for the delayed
recall effect. Concurrent with other research (McCabe & Loaiza, 2010; Unsworth & Engle,
2007), more attentional resources are engaged during complex span tasks to retrieve and
maintain the items for longer periods of time. Specifically, the processing component of the
operation span task is used as an opportunity to refresh the to-be-remembered item in order to
maintain that item. Based on the embedded-process model in which working memory is defined
as an activated portion of long-term memory (Cowan, 1999), items processed during the simple
span task are held in the focus of attention. Alternatively, the processing portion of complex
span tasks results in a shift of attention between the to-be-remembered item and the operation
task itself, resulting in displacement from the focus of attention (McCabe, 2008; McCabe &
Loaiza, 2010). The covert retrieval model suggests that subjects use some of the time during the
processing phase to attentionally refresh, or covertly retrieve, the to-be-remembered items, and
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indicates that this maintenance process is important for long-term retention of information
(McCabe, 2008).
The Embedded-Process Model
The delayed recall effect allows the relationship between working memory and long-term
memory to be examined directly (McCabe & Loaiza, 2010). Cowan’s embedded-process model
(1999) explains the focus of attention, activated long-term memory, and long-term memory as
functionally distinct components, which each factor being more highly activated than the next.
The focus of attention is thought to be capacity limited, in that it can only retain approximately 3
to 5 items at a given time (similar to Unsworth & Engle’s (2006) concept of primary memory),
while the temporarily activated subset of long-term memory is limited by duration (Cowan,
1999; 2008). By covertly retrieving information, participants can keep the to-be-remembered
items available in activated long-term memory so they are more readily available for subsequent
recall (McCabe, 2008; McCabe & Loaiza, 2010). It is also thought that the time used to
attentionally refresh items during covert retrieval opportunities provides retrieval cues that can
aid performance on delayed recall tests (McCabe & Loaiza, 2010). By controlling for the
amount of time allotted for covert retrieval, covert articulation, and number of covert retrieval
opportunities results by McCabe & Loaiza (2010) rule out any alternative arguments and indicate
that the delayed recall effect actually is determined by attentional refreshing. Findings support
the idea of focus of attention and other components as being functionally separate, as suggested
by Cowan (1999), and these delayed recall data are generally consistent with the embeddedprocess model (McCabe & Loaiza, 2010). Items that are presented from simple span tasks are
more easily retrieved than those from complex span tasks at immediate recall because they are
being reported directly from the focus of attention, while to-be-remembered items presented with
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operation span must be retrieved from secondary memory. It is due to attentional refreshing that
complex span items can be brought back into the focus of attention from the activated portion of
long-term memory (McCabe & Loaiza, 2010).
Levels of Processing and Semantic Networks
According the Craik and Lockhart’s (1972) conception of levels of processing,
information is processed hierarchically with greater depth entailing greater cognitive analysis.
Items that are more familiar or have more extensive semantic networks will be processed more
quickly than items that lack pre-existing semantic representations. Therefore, there is an
increase in performance on delayed recall tests for items that were initially encoded at a deep
level of processing, such as semantic characteristics, rather than items that were encoded for
physical characteristics, which would be considered a shallow level of processing (Craik &
Lockhart, 1972). When subjects encounter to-be-remembered items during span tasks, they are
initially processed phonologically, for the sound of the word, and then the semantic
representation is activated so the meaning of the word can be accessed. On the contrary, items
that are lacking long-term semantic networks, such as non-words, can only be encoded at a
phonological level and therefore do not have the potential for high levels of activation within the
activated long-term memory. Lower levels of activation within the activated long-term memory
will make attentional refreshing more difficult, because the item must be retrieved from the
activated long-term memory back into the focus of attention (Cowan, 1999).
Research Proposal
In replication of McCabe (2008), the delayed recall effect is tested with both word and
nonword stimuli. If attentional refreshing in working memory is a domain-general function, the
type of stimuli should be irrelevant making the maintenance of information for long-term
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retention effective regardless of whether the stimuli had pre-existing semantic networks.
Alternatively, attentional refreshing may rely on these long-term semantic networks to function,
thus the delayed recall effect may only be seen when words are used as stimuli. By using nonwords in addition to words, it is tested whether pre-existing representations are necessary for
items to be attentionally refreshed. Because refreshing is such a brief process, it is hypothesized
that words will be easier to refresh than non-words, as they already have pre-existing semantic
representations in long-term memory.
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References
Baddeley, A., & Logie, R. (1999). Working memory: The multiple-component model. Models of
working memory: Mechanisms of active maintenance and executive control (pp. 28-61).
New York, NY US: Cambridge University Press.
Cowan, N. (1993). Activation, attention, and short-term memory. Memory & Cognition, 21(2),
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Cowan, N. (1999). An Embedded-Processes Model of working memory. In: Miyake A. and Shah
P. (Eds.), Models of Working Memory: Mechanisms of Active Maintenance and
Executive Control. Cambridge University Press, Cambridge, UK, pp. 62-101.
Cowan, N. (2008). What are the differences between long-term, short-term, and working
memory? Progress in Brain Research, 169, 323-338.
Craik, F., & Lockhart, R. (1972). Levels of processing: A framework for memory research.
Journal of Verbal Learning & Verbal Behavior, 11(6), 671-684.
Daneman, M., & Carpenter, P. (1980). Individual differences in working memory and reading.
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McCabe, D.P. (2008). The role of covert retrieval in working memory span tasks: Evidence from
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McCabe, D.P. & Loaiza, V. (2010). The relationship between working memory and episodic
memory: Differential effects of available time and number of opportunities for covert
retrieval. Manuscript submitted for publication.
Miyake, A., & Shah, P. (Eds.) (1999). Models of working memory: Mechanisms of active
maintenance and executive control. New York, NY US: Cambridge University Press.
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Unsworth, N., & Engle, R. (2006). Simple and complex memory spans and their relation to fluid
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