Running Head: MIND WANDERING AND WORKING MEMORY
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Working Memory: modulating Task-Unrelated Thoughts and their subsequent effects
on Task Performance
Dima Obari
American University of Beirut
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Mind Wandering, also know as task-unrelated thoughts, is still a developing
topic in psychology. It is defined as the shift in attention from the task being
performed to thoughts that are irrelevant to the task. Typically, half our daily life is
spent mind wandering (Levinson, Smallwood & Davidson, 2012). Recent studies
have sought to explain individual differences in mind wandering propensity in terms
of differences in working memory capacity. In fact, extensive research has undertaken
the study of the nature of the relationship between working memory capacity and
mind wandering. Two main, conflicting approaches are of importance to us here.
While the resource-demanding view proposes that working memory resources are
required for the maintenance of task-unrelated thoughts (Smallwood, 2010), the
control failure x concerns view maintains that mind wandering in fact represents a
failure of working memory to inhibit task-related thoughts (McVay & Kane, 2012).
For our purposes, we will first proceed by integrating both approaches along with
their opposing findings, by taking a third factor into account: task demands. Then we
will conclude with the effects of mind wandering on the processing of external
stimuli, both relevant and irrelevant to task performance.
According to Smallwood (2010), mind wandering is a phenomenon that albeit
is initiated in a spontaneous manner, relies on working memory resources. Thus, one
would expect that the propensity to mind wander should vary according to the
availability of those resources. That is, when the task performed places a high demand
on cognitive resources, mind wandering should decrease. Indeed, Forster & Lavie
(2009) manipulated perceptual load in a series of perceptual search tasks by changing
the number of search items. They found that, as the perceptual load increased,
participants reported less task unrelated thoughts, a finding that was consistent across
all four conducted experiments. Furthermore, in an experiment requiring the
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generation of random numbers, participants produced significantly less random
sequences of numbers following stimulus-independent thoughts (SITs) compared to
no-thoughts (NTs). This suggests that when mind wandering did occur, it caused a
decrease in performance as a result of the sharing of cognitive resources (Teasdale, et
al., 1995).
Interestingly, in another experiment, by Teasdale, Proctor, Lloyd & Baddeley
(1993), this negative correlation between mind wandering and performance was not
found when the task did not significantly tax working memory. Indeed, when
participants were required to remember a single digit rather than five, the
experiencing of task-unrelated thoughts, though associated with a lower level of
awareness of the digits, did not interfere with memory performance, which was
perfect on all trials. Moreover, Mason et al. (2007) found that mind wandering
increased during performance on practiced blocks of working memory tasks, as
compared to novel blocks. Thus they concluded that practice resulted in a decrease in
processing demands, which allowed more resources to be allocated to mind
wandering.
So far, the evidence reviewed was in favor of a view of working memory that
facilitates mind wandering by providing it with the required resources, when the latter
are available. However, McVay & Kane (2010) proposed an alternative explanation
for the decrease in mind wandering associated with high-demanding tasks. According
to them, when the task necessitates cognitive resources, working memory inhibits
task-unrelated thoughts by focusing attention on the current task. Thus, mind
wandering represents a failure of attention control and, consequently, a limitation of
working memory capacity. Their argument is based on the findings that individuals
with higher working memory capacity, who, according to the resource-demanding
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view, should have more resources to mind wander, actually reported less taskunrelated thoughts (McVay & Kane, 2009).
This argument is in accordance with the control failure x concerns approach,
where mind wandering propensity is determined by the executive control system’s
efficiency in dealing with interference. This system consists in two main components,
each of which was associated with different brain regions. On one hand, proactive
control is necessary for maintaining on-task thought throughout the task and is
accompanied by an increase in activity in the dorsal lateral prefrontal cortex. On the
other hand, reactive control is introduced when proactive control fails, as to suppress
any off-task thought that has surfaced in response to a cue and that may cause a
conflict with on-task thought. It is associated with higher activation of the anterior
cingulated cortex. This division was based on a neuroimaging study that revealed a
double dissociation between the two components (MacDonald, Cohen, Stenger &
Carter, 2000). In another study involving a stroop task, Kane & Engle (2003)
examined how individual variation in working memory capacity affected attention
control. They found, consistent with the executive attention model, that individuals
with lower working memory capacity had more difficulty with incongruent trials (for
example, the word GREEN written in red ink), relative to those with higher working
memory capacity. However, they were faster on congruent trials (GREEN written in
green ink). This shows that they were reading the words instead of reporting the color
of the ink, as requested from them, thus revealing a problem with goal maintenance (a
type of proactive control). Additionally, they remained slower on incongruent tasks
when the goal was made accessible to aid with proactive control, suggesting also a
problem with resolving the competition between the color’s written name and the
color of the ink (a type of reactive control).
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This view also takes into account the current concerns of the participants, cued
by the context in which the task is being performed. Indeed, Antrobus, Singer &
Greenberg (1966) tested the assumption that task-unrelated thoughts are generated
spontaneously when individuals are presented with information that does not match
the expectations they have of the future. For that matter, they presented the
experimental group with a false broadcast stating that communist China has
announced war to the United States, before they had them complete a simple signal
detection task. Relative to the control group who did not hear the broadcast,
participants experienced more spontaneous, off-task thoughts during the task. In
another study, Klos & Singer (1981) measured adolescents’ history of interpersonal
stress with a parent, and had them simulate either a coercive, or a collaborative
confrontation with that parent. They then measured their levels of affect arousal and
the frequency of repetitive thoughts they experienced afterwards. They found that,
when knowledge of the person’s stress history was added to knowledge of the
situation, this led to a significantly better prediction of both affective and cognitive
responses. Indeed, participants with a long-standing history of interpersonal stress
who simulated the coercive confrontation experienced more repetitive thoughts, as
they had to cope with both internal (stress history) and external (simulation of the
confrontation) sources of affect. Thus repetitive cognition is determined not only by
situational cues, but also by self-generated determinants pertaining to the participants’
past, a finding that is supported by the control failure x concerns approach to mind
wandering. Finally, Giambra (1989) found an inverse relationship between age and
task-unrelated thoughts, a finding that was consistent across all of the five
experiments he had conducted. This could be explained by the hypothesis that older
adults have fewer concerns, and thus are less subject to internal sources of
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interference. Carlton, Klinger & Perlmutter (1988) did indeed obtain a correlation
between concerns and mind wandering in older adults. Indeed, in their study, older
participants reported a lower number of current concerns, and engaged in fewer taskunrelated thoughts during task performance, as compared to college students.
Thus far, we have reviewed two conflicting approaches of mind wandering;
one supports that mind wandering necessitates working memory resources (resourcedemanding view), while the other attributes an inhibitory influence to working
memory over task-unrelated thoughts (control failure x concerns view). A more recent
study by Levinson, Smallwood & Davidson (2012) attempted to integrate both
models by having participants complete tasks that placed minimal demands on
cognitive resources. For that mater, they had participants complete a low-load visual
task and a breath-awareness task, and found that, consistent with the resourcedemanding view, participants with greater working memory capacity mind wandered
more during both tasks. However, they interpreted their findings by attributing a dual
role to working memory, which, they argued, modulates mind wandering according to
the situational demands created by the task being performed. However, do these
objective laboratory findings generalize to more natural settings? In an experience
sampling method of daily life, Kane, Brown, Little & Sylvia (2007) found that while,
individuals with higher memory capacity experience more off-task thoughts when
they were not trying to concentrate, their mind wandering decreased when they
deliberately focused attention on the task, which is in accordance with laboratory
research results.
We will now turn to a third approach, the decoupling hypothesis, which
maintains that, contrary to the control failure x concerns view, mind wandering does
not represent an instance of failure to maintain attention on task-relevant stimuli, but
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consists in fact in one’s attention being turned away from all external stimuli, toward
one’s internal thoughts. Perhaps the best supporting evidence of this view comes form
an experiment conducted by Barron, Singer & Greensberg (2012), in which eventrelated potentials in relevant brain areas where measured while participants conducted
an oddball task, thus allowing an ongoing assessment of attention. Two components,
P3a and P3b were studied; variation in the amplitude of the P3a component indicated
the level of external distraction, while variation in the P3b component was used as an
index of the attention allocated to task relevant stimuli. These measures were
followed by retrospective self-reports that allowed to assess the frequency of taskunrelated thoughts and thus to separate participants into a low and a high taskunrelated thoughts groups. The experimenters observed that the group that was higher
in task-unrelated thoughts had lower amplitudes for both the P3a and P3b
components. Thus they concluded that mind wandering involves a decrease in the
processing of both task-relevant and task-irrelevant thoughts. The decoupling
hypothesis thus suggests that mind wandering consists in the decoupling of attention
from all external, perceptual stimuli, regardless of their relevance. It thus insulates the
internal train of thoughts in order to prevent interference form external perceptual
events.
All in all, when the tax being performed places high demands on cognitive
processes, working memory prevents task-unrelated thoughts from surfacing by
the means of proactive and reactive processes, thus focusing attention on the
task being performed. However, when the task is more permissive for mind
wandering to occur, working memory not only facilitates task-unrelated
thoughts, but also protects them from interference by limiting the processing of
all external stimuli, regardless of relevance.
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