What limits dual-tasking in working memory? An investigation of the effect of sub-task demand on maintenance mechanisms employed during dual-tasking
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Date
28/11/2016Item status
Restricted AccessEmbargo end date
31/12/2100Author
Doherty, Jason Michael
Metadata
Abstract
A number of models of working memory have been proposed since the seminal work of
Baddeley and Hitch (1974) on the Multiple Component Model (MCM). Subsequent
MCM research focussed on developing a theoretical framework based on modality-specific
stores that can operate in parallel during dual-tasking. The MCM can be
contrasted with theories of working memory that assume an attention-based domain-general
shared resource responsible for both short term retention as well as on-line
cognition, such as the Time-Based Resource Sharing (TBRS) model (Barrouillet,
Bernardin, & Camos, 2004; Barrouillet, Bernardin, Portrat, Vergauwe, & Camos,
2007). The TBRS model assumes that short-term memory is dependent on access to
attention, and any diversion of attention results in increased forgetting. The model
describes ‘refreshing’ as the process of serially bringing memory items briefly into the
focus of attention. Barrouillet and colleagues have demonstrated in numerous studies
that memory spans lower as the cognitive demand of the secondary task increases
- findings that are incompatible with the MCM. However, Camos, Mora, and Oberauer
(2011) found that both sub-vocal rehearsal (the verbal maintenance mechanism
described in the MCM) and attention-based refreshing can be selectively employed
by participants depending on task demands. Since TBRS methodology compares
spans measured under different cognitive load levels that are the same for every participant,
we were interested in whether ensuring that secondary task demand was set
within each participant’s abilities would avoid ‘over-taxing’ the working memory system
and reduce dual-task costs. Our initial investigations re-measured memory and
processing spans under dual-task conditions with secondary tasks’ demand titrated
according to each individual’s measured ability (Experiments 1 and 2, and Doherty &
Logie, 2016). We found that memory span was unaffected when processing demand
was titrated, but that processing performance was lower when memory load was set
above participants’ span. Subsequent experiments (3-8) investigated the effect of setting
memory and processing load ‘below span’, ‘at span’, and ‘above span’ on memory
and processing accuracy during dual-tasking. Overall it was found that processing
resources can be reallocated to support memory performance but memory resources
cannot be reallocated to support processing performance. We interpret the results
as evidence for specialised memory resources and rehearsal mechanisms that can
be supplemented by attention-based processes once storage capacities are exceeded.
Experiments 6-8 aimed to encourage the use of phonological- or attention-based rehearsal
mechanisms for verbal short term memory by either introducing articulatory
suppression (AS) or shortening available encoding time for memory items. It was
found that participants exhibited shared-resource effects when they completed the
dual-task under AS, suggesting a shift to attention-based rehearsal. When encoding
time was limited participants’ memory performance during dual-tasking was unaffected
by concurrent processing load, suggesting the use of a rehearsal method which
did not require access to attention. Experiment 9 investigated whether participants
could dynamically allocate attention to one task or the other, and found that while
‘priority’ tasks received no benefit, non-priority tasks exhibited a marked decrement
in performance. We conclude that the perceived incompatibility between the MCM
and attention-based theories of working memory such as the TBRS model may be
more apparent than real, and suggest that future research should incorporate procedures
and methodological considerations that take into account findings from both
literatures.