Psychology
2013. Vol.4, No.3A, 224-231
Published Online March 2013 in SciRes (http://www.scirp.org/journal/psych) http://dx.doi.org/10.4236/psych.2013.43A034
224
Rumination, Mood and Cognitive Performance
Jay K. Brinker, Mel Campisi, Laura Gibbs, Rebekah Izzard
Research School of Psychology, The Australian National University, Canberra, Australia
Received October 29th, 2012; revised December 10th, 2012; accepted January 9th, 2013
Rumination, DEFINED AS REPETITIVE, RECURRENT AND UNCONTROLLABLE THINKING, has
been implicated in cognitive impairments, particularly dysexecutive function, in people with depressed
mood, what is now critical is an examination of the link between rumination and cognitive impairment
independent of mood. Rumination’s direct relationship to basic cognitive functions may help explain the
stability of rumination, and how it predicts future episodes of depressed mood. Two experiments exam-
ined how trait and experimentally induced rumination, and negative mood relate to attention and inhibi-
tion at varying levels of cognitive load in non-depressed participants. Study 1 found trait rumination sig-
nificantly predicted errors of attention when cognitive load was low or high, but not at a medium level.
Trait rumination also interacted with frequency of task unrelated thoughts to predict performance. Nega-
tive mood significantly predicted errors of inhibition also when the cognitive load was low or high. Study
2 expanded on the first by including two additional measures of executive function. Results were repli-
cated for the first study and showed a ruminative thought style predicted inhibition, reaction time and set
shifting in the additional measures.
Keywords: Rumination; Mood; Executive Functions; Cognitive Load; Off-Task Thoughts
Introduction
There are many ways to conceptualise rumination; a response
to depressed mood (Nolen-Hoeksema, Parker, & Larson, 1994;
Verhaeghen, Joorman, & Khan, 2005), an emotion regulation
strategy (Nolen-Hoeksema, Wisco, & Lyubomirsky, 2008), a
form of self-focused attention (Mor & Winquist, 2002), as a
process or style of thinking (Brinker & Dozois, 2009) and so on.
These conceptions are not necessarily contradictory, but simply
different ways of considering and examining a complex phe-
nomenon. In its most general sense, rumination is a style of
thinking characterised by repetitive, recurrent, intrusive and un-
controllable thoughts (Brinker & Dozois, 2009). The relation-
ship between rumination and cognitive impairment has been
demonstrated, but what is not known is 1) the relationship be-
tween rumination and cognition independent of depressed
mood; and 2) examination of the causal relationship between
rumination and impairment. These may be addressed by meas-
uring rumination as an individual difference in a non-depressed
sample using a measure of the process of rumination, and by
experimentally manipulating rumination to observe changes in
cognitive performance.
Within the different conceptions of rumination, it is generally
agreed that rumination is a stable phenomenon (Brinker & Do-
zois, 2009; Nolen-Hoeksema, Wisco, & Lybomirsky, 2008)
with serious clinical implications due to the consistent rela-
tionship with depressed mood. Rumination is related to greater
depressed mood, longer depressive episodes and the occurrence
of future depressive episodes (Brinker & Dozois, 2009; Nolen-
Hoeksema, Wisco, & Lybomirsky, 2008). The link to future
episodes of depression raises two important points. First, even
when negative mood is ameliorated, the process of thinking in a
ruminative style may continue, and the vulnerability posed by
rumination may continue. Second, the stability of ruminative
thinking suggests the process may be related to individual dif-
ferences in basic cognitive function—in particular executive
functioning.
Executive functions are a group of cognitive abilities that
enable goal directed behaviour including attentional control,
inhibitory systems and cognitive flexibility. Regardless of con-
tent, ruminative thoughts reflect an unintentional shift in atten-
tion away from the task at hand (Martin & Tesser, 1996), and
the failure of cognitive inhibitory systems to limit attention to
task-relevant information (Carson, Peterson, & Higgins, 2003;
Hertel, 1997; Joormann, 2004). In other words people who ru-
minate are unable to inhibit the ruminative thoughts and main-
tain attention elsewhere.
Research has demonstrated a relationship between rumina-
tion and attentional inflexibility (Davis & Nolen-Hoeksema,
2000; Lo, Lau, Cheung, & Allen, 2012). Watkins and Brown
(2002) suggest that rumination reduces cognitive flexibility by
overloading cognitive resources, primarily in the form of defi-
cits in switching and inhibition (Miyake et al., 2000). Whit-
mer and Banich (2007) suggest that switching attention from
one conceptual set to another is difficult for individuals who
ruminate and show rumination is linked to difficulties with
inhibiting previously relevant task sets in a non-depressed sam-
ple. Davis and Nolen-Hoeksema (2000) also found evidence for
attentional inflexibility, with ruminators making more per-
severation errors on the Wisconsin Card Sorting Test and tak-
ing more time on a measure of psychomotor speed compared to
non-ruminators.
As mentioned, Watkins and Brown (2002) argue perform-
ance impairment may result from limited cognitive resources,
and rumination may further consume resources that would oth-
erwise be directed towards the primary task. Increasing the
cognitive demands of the current external task has been found
to lead to a reduction in the frequency of off-task thoughts (e.g.

J. K. BRINKER ET AL.
Teasdale et al., 1995). Antrobus (1968) observed that increas-
ing the speed of stimulus presentation in a signal-detection task
increased the cognitive demands for processing task related
information, resulting in an improvement in task performance.
This was attributed to more cognitive resources needing to be
directed towards the task, leaving fewer cognitive resources
available for the production of off-task thoughts. These results
suggest that attention-demanding tasks may disrupt rumination
(Teasdale et al., 1995). Lyubomirsky and colleagues (2003)
tested the effect of dysphoric rumination on participant’s per-
formance on three academic tasks (reading a passage, watching
a videotaped lecture and proofreading written text) and found
that decrements in task performance tended to be greater for
tasks with mild to moderate difficulty. Lyubomirsky and col-
leagues (2003) also found that dysphoric participants who ru-
minated were slower at the tasks than the other comparison
groups even if their accuracy was equivalent.
Typically, rumination is tested in participants experiencing
dysphoric mood (natural or induced) with much research sug-
gesting it is the combination of negative mood and rumination
that produces effects (Lyubomirsky, Kasri, & Zehm, 2003).
However, there is reason to suppose that a ruminative style of
thinking may be related to impaired executive functions re-
gardless of mood. The previous research examining intrusive
thoughts, inhibition and executive function in relation to cogni-
tive performance illustrates differences in non-depressed sam-
ples without inducing negative mood (Carson, Peterson, & Hig-
gins, 2003, Teasdale et al., 1995, Whitmer & Banich, 2007).
Rumination has been linked to executive function (Davis &
Nolen-Hoeksema, 2000) and Williams, Suchy and Rau (2009)
argue that there are individual differences in executive function
both in conjunction with and independent of mood. Given the
firm basis of research in rumination and depression combined,
it is now time to examine the influence of rumination in a
non-depressed sample without inducing negative mood. It is
hypothesised that rumination, even in the absence of depressed
mood, will be related to impairment in executive function.
Study 1
Several variables are involved when considering the above
findings; attention, inhibition, cognitive load, task unrelated
thoughts and both trait and induced rumination. This project
will examine these variables together by employing a continu-
ous performance task to directly manipulate cognitive load and
measure attention and inhibition. Further, a baseline measure of
trait rumination and experimentally induced rumination will be
included. It is hypothesised that participants in the rumination
condition will show poorer performance than those in a distrac-
tion condition, on attention and inhibition when cognitive load
is low. It is also predicted that participants high on trait rumina-
tion will perform more poorly than those with low trait rumina-
tion. Finally, greater frequency of off-task thoughts will be
related to poorer cognitive performance.
Method
Participants
One-hundred first year psychology students (31 male and 69
female) from the Australian National University participated in
the study ranging in age from 17 - 57 years (M = 19.83, SD =
4.77). Participants WERE RECRUITED VIA POSTERS
PLACED AROUND THE DEPARTMENT AND ON THE
FIRST YEAR COURSE WEBSITE. THEY received one hour
of course credit for their participation. THERE WAS NO SET
INCLUSION OR EXCLUSION CRITERIA AND PARTICI-
PANTS WERE NOT RECRUITED BASED ON PREVIOUS
MENTAL HEALTH HISTORY.
Materials
Positive and Negative Affect Schedule (PANAS-X; Watson
& Clark, 1994): THIS MEASURE WAS INCLUDED TO
CONTROL FOR BASELINE MOOD. The PANAS consists of
20 mood adjectives: 10 positive (PANAS-P) and 10 negative
(PANAS-N). Respondents are asked to rate on a 5-point scale
the degree to which they have experienced each of these moods
in the past 24 hours. The scale ranges from 1 (not at all) to 5
(very much). These scales were used as a baseline measure of
the degree of positive and negative affect participants were
experiencing prior to completing the study. The Chronbach’s
alphas for this study were .87 for the PANAS-P and .85 for the
PANAS-N.
Ruminative Thought Styles Questionnaire (RTS; Brinker &
Dozois, 2009). The RTS is a measure of a general ruminative
thought style characterised by repetitive, recurrent, intrusive
and uncontrollable thinking. It consists of 20 statements that
respondents rate as self descriptive or not on a Likert-type scale
from 1—not at all like me to 7—very much like me. The total
scores range from 20 to 140 with higher scores indicating
greater ruminative thinking. The RTS shows good internal re-
liability (α = .87 to .92), good test-retest reliability (r = .80) and
good convergent and divergent validity (Brinker & Dozois,
2009). Cronbach’s alpha for the current study is .91.
Rumination/Distraction Induction (Lyubomirsky & Nolen-
Hoeksema, 1993): This task IS THE EXPERIMENTAL MA-
NIPULATION AND was designed to induce either a rumina-
tive or distractive style of thought in participants, and has been
widely used in rumination research (e.g. Rimes & Watkins,
2005; Watkins & Moulds, 2005; Lyubomirsky, Kasri, & Zehm,
2003). The rumination condition asks participants to think
about a series of 45 self-focused statements, (e.g. “think about
what your feelings might mean”), and is designed to focus par-
ticipants on the meaning, causes and consequences of their
current feelings (Nolen-Hoeksema, Wisco, & Lyubomirsky,
2008). The distraction condition required participants to focus
on 45 statements designed to shift participants’ focus away
from themselves, (e.g. “think about a boat sailing on the
ocean”). Each induction lasted for eight minutes. While these
are typically used with individuals currently experiencing de-
pressed mood they may be of use with a healthy sample by
inducing self-focused attention, a component of the ruminative
response style.
Continuous Performance Task (CPT): THIS TASK MEAS-
URES ATTENTION AND INHIBITION—THE DEPEND-
ENT VARIABLE. Participants completed a computer task
involving attending to a series of letters presented on the screen
and responding by pressing the space bar whenever an “X” was
presented. Letters were presented in nine blocks of 20 letters,
five of which were “X”s in each block. All letters were dis-
played for 250 ms each. The inter-stimulus intervals were 1, 2
and 4 seconds (fast, medium and slow speeds, respectively)
creating 3 levels of cognitive load—high, medium and low.
Participants viewed three blocks for each of the speeds. Par-
ticipants were also given a ‘practice round’ before commencing

J. K. BRINKER ET AL.
the task. The task took approximately eight minutes to complete,
and produced two outcome measures for each of the speeds:
number of correct hits (attention) and number of false hits
(failure to inhibit). Because the key comparison is across ex-
perimental groups, not across speed blocks, the order of pres-
entation speed was held constant for all participants.
Off-Task Thoughts: Following the CPT, participants reported
the type and frequency of off-task thoughts they experienced
AS A POSSIBLE MEDIATING VARIABLE. Participants
reported frequency of task related and unrelated thoughts, and
frequency of repeating thoughts using Likert scales ranging
from 1 (not at all) to 7 (frequently).
Mood Rating Scale: A visual analogue scale (VAS) was in-
cluded as a brief, repeatable mood measure to assess changes in
participant’s mood throughout the study. Based on Lyubomir-
sky & Nolen-Hoeksema’s (1995) measure, participants were
asked to indicate the degree of positive or negative affect they
were currently experiencing by moving a marker up or down a
100 mm line representing a continuum from 0 (extremely nega-
tive affect) to 100 (extremely positive affect). Higher scores on
these reflect lower negative mood.
Procedure
Participants completed the study in a computer lab in groups
of 5 - 10 and were randomly assigned to either the rumination
or distraction condition. All sections of the study were pre-
sented and completed by participants on computer, and partici-
pants simply clicked on the “Next” button to move through the
protocol. Participants first completed the PANAS-X and the
first visual analogue scale mood measure (Mood 1) to assess
their baseline mood, and the RTS to assess their trait ruminative
thinking style. THESE VARIABLES ACT AS CONTROL
WHEN EXAMINING THE EFFECT OF THE EXPERIMEN-
TAL MANIPULATION. They were then presented with their
assigned induction procedure. Participants were asked to rate
their current mood using a second visual analogue scale (Mood
2) and then complete the Continuous Performance Task. Par-
ticipants reported the off-task thoughts they experienced during
the CPT and completed a final VAS (Mood 3).
Results and Discussion
T-tests revealed no significant between group differences for
age (t = –1.46, p = .15) or mood as measured by the PANAS
(positive mood t = –.70, p = .49; negative mood t = 1.62, p
= .11) and VAS1 prior to the induction (t = –.87, p = .34).
However, despite participants being randomly assigned to con-
ditions, there was a significant difference between experimental
groups on baseline ruminative thought styles (t = 2.23, p < .05)
with the rumination group reporting higher levels of trait rumi-
native thought than the distraction group (M = 91.06 and 83.24
respectively). Because of this, analyses examining the RTS will
be interpreted with caution.
Correlations were conducted to examine the relationships
between baseline measures prior to the inductions (Table 1).
All correlations were significant and in the expected direction
(Papageorgiou & Siegle, 2003) with GREATER rumination
being significantly related to greater negative mood as meas-
ured by the PANAS-N and the visual analogue scales.
Group comparisons on post induction differences in mood
show the inductions produced a difference in mood between the
groups that was near to significance (t = 1.946, p = .06). Be-
cause of the imbalance in RTS scores across the experimental
groups, with the rumination group having higher RTS scores,
this difference in post-induction mood may be an artifact of
assignment bias due to the high correlation between ruminative
thought styles and negative mood. Hierarchical linear regres-
sion examined the prediction of post induction mood, with
baseline mood entered in the first step, and induction condition
and trait rumination entered into the second step. Only baseline
mood (β = –.223, p = .03) and ruminative thought style (β =
–.507, p = .000) were significant predictors.
Linear regression analyses predicted performance on the six
CPT variables (i.e. correct and false hits for each of the 3 levels
of cognitive load). Baseline mood was entered into the first step,
with RTS score and induction condition entered in the second.
For correct hits, as a measure of attention, RTS score was a
significant predictor at both the high and low cognitive load but
not the medium (Table 2). Mood was a significant predictor of
Table 1.
Baseline correlations.
PANAS-N Mood 1 M SD
RTS .540** –.604** 87.15 17.91
PANAS-N –.444** 20.47 7.05
Mood 1 .673 .208
Note: **p = .01.
Table 2.
Predicting cognitive performance by degree of cognitive load control-
ling for baseline mood.
False Hits (Inhibition) Correct Hits (Attention)
High Load B SE B  B SE B
Step 1
Mood .034.009 .362 –.040 .008–.444**
Step 2
Mood .031.011 .329** –.013 .008–.147
RTS Score .003.004 .085 –.021 .003–.575**
Condition .113.129 .085 –.110 .101–.086
Medium Load
Step 1
Mood .001.001 .036 .000 .007–.002
Step 2
Mood –.001.002 –.038 .004 .009.053
RTS Score .001.001 .115 –.004 .003–.149
Condition –.016.021 –.081 –.165 .105–.161
Low Load
Step 1
Mood .086.012 .600** –.090 .015–.514**
Step 2
Mood .093.014 .649** –.029 .014–.168*
RTS Score –.006.005 –.106 –.044 .006–.644**
Condition –.105.166 –.052 –.011 .171–.005
Note: *p < .05; **p < .01.
226

J. K. BRINKER ET AL.
correct hits, but only when cognitive load was low. For false
hits, as a measure of failed inhibition, only baseline mood was a
significant predictor, but again, only at high or low cognitive
load (Table 2).
In relation to inhibition, it appears that mood alone accounts
for variance in scores at fast and slow speeds. This supports the
previous literature showing that negative mood is related to
cognitive deficits (Austin, 2001). In particular, Koster, De Lis-
snyder, Derakshan and De Raedt (2011) propose the impaired
disengagement hypothesis as a comprehensive explanation of
the neurocognitive basis of these findings. This theory suggests
that individuals encounter some stressor that prompts self-re-
flective/negative thinking.
Some individuals are unable to disengage from this negative
thinking leading to prolonged rumination and subsequently task
impairments and negative mood. This model is circular with
negative mood feeding back into the loop at the point where the
person fails to disengage from the self-reflective/negative
thinking. The current findings linking negative mood to re-
duced ability to inhibit responses, may be one mechanism by
which this happens—these individuals are unable to inhibit the
self-reflective/negative thoughts. Disengagement may be fur-
ther hampered by the person’s inability to maintain attention
elsewhere due to the ruminative style of the self-reflective/
negative thinking.
Scores on the ruminative thought styles scale predicted errors
of attention after controlling for negative mood. It appears that
mood and ruminative processes each relate to a different im-
pairment in abilities needed to disengage from maladaptive
thoughts and engage their attention elsewhere. The common co-
occurrence of rumination and mood may be a particularly pow-
erful vulnerability.
Following the continuous performance task, participants
were asked to report the frequency of off-task thoughts in gen-
eral, off-task thoughts directly related to the induction proce-
dure and frequency of repeating thoughts. The two induction
groups did not significantly differ in the self-reported frequency
of these thoughts. However, the RTS significantly predicted
general off-task thought frequency, even when controlling for
baseline negative mood and induction condition (β = .241, p
= .05). Hierarchical regressions were used to further explore the
predictive ability of ruminative thought styles and off-task
thoughts on task performance.
Baseline mood was entered into the first step, the main ef-
fects of RTS score and frequency of off-task thoughts were
entered into the second step, and the interaction of these two
variables was entered into the third (Table 3). Ruminative
thought style and frequency of off-task thoughts interacted to
significantly predict errors of attention when cognitive load was
high or low. As suggested by previous research, increasing
cognitive demands may improve performance by preventing the
intrusion of off-task thoughts, but there may be a point where
the demands are too great and a decrement in performance is
seen (Lyubomirsky et al., 2003; Teasdale et al., 1995). These
results suggest it is the combination of a ruminative style of
thinking and the experience of off-task thoughts that predicts
impaired performance.
The results of this study are very interesting and speak to the
possible differential effects of a ruminative thought style and
negative mood. The separation of these two variables may be
artificial because of their high co-occurrence, but recognition of
this divide may have important consequences for treatment.
Table 3.
Rumination and off task thoughts predicting attention.
Correct Hits (Attention)
High Load B SE B
Step 1
Baseline Mood –.040 .008 –.444**
Step 2
Baseline Mood .031 .011 .329**
RTS Score .003 .004 .085
Frequency of Off Task Thoughts .113 .129 .085
Step 3
Baseline Mood –.010 .008 –.113
RTS Score –.003 .008 –.081
Frequency Off Task Thoughts .427 .199 .774*
RTS × Frequency Off Task Thoughts –.005 .002 –1.051*
Low Load
Step 1
Mood .086 .012 .600**
Step 2
Mood .093 .014 .649**
RTS Score –.006 .005 –.106
Condition –.105 .166 –.052
Step 3
Baseline Mood –.022 .013 –.126
RTS Score .001 .013 .013
Frequency Off Task Thoughts 1.157 .321 1.085**
RTS × Frequency Off Task Thoughts –.014 .004 –1.454**
Note: *p < .05; **p < .01.
While depressed mood may be ameliorated by treatment, the
lingering ruminative thinking style may remain as the link to
future episodes of depressed mood (Brinker & Dozois, 2009).
Trait rumination predicted frequency of off-task thoughts and
the interaction of these predicted impaired performance in the
absence of depressed mood. This speaks to the importance of
stable ruminative thinking styles occurring in everyday life and
the impact it may have on cognitive processes. However, the
inequity between groups on RTS scores requires confirmation
with a second sample to confidently draw conclusions.
Study 2
The unexpected group differences in RTS scores in the first
sample need to be addressed to confirm the findings from study
1 and provide a clearer understanding of how the constructs of
ruminative thought style, mood and cognitive performance are
related. This second study replicates the first but with the ex-
clusion of the unrelated thoughts measure and the addition of
two new measures of cognitive flexibility—The Wisconsin Cart
Sorting Task, and the Simon Task. The Wisconsin Card Sorting
Task (WCST) is a measure of perseveration—a presentation of
the inability to shift set. This task was designed to assess brain
pathology and therefore may not be sensitive enough to assess

J. K. BRINKER ET AL.
individual differences in a healthy population. Given this po-
tential limitation, the Simon Task, a computer based measure of
inhibition based on the Stroop task, was included having been
successfully used in analogue studies using non-impaired sam-
ples (Simon, 2010).
Method
Participants
One hundred and twenty eight participants completed the
current study. The majority of these participants were first year
psychology students at the Australian National University par-
ticipating as a course requirement. The remaining participants
included senior level psychology student volunteers and volun-
teer community members. The study included 65% females and
35% males, with an age range of 18 - 62 (M = 22.3, SD = 9.54);
58% were Caucasian.
Materials
In addition to the materials repeated from study one, this
study includes.
Wisconsin Card Sorting Task (WCST; Grant & Berg, 1948).
Grant and Berg (1948) designed this task as a measure of set
shifting ability. Participants match response cards at the top of
the screen to one of four stimulus cards at the bottom of the
screen. The response cards were four different possible colours
(blue, red, green and yellow), numbers (1 through 4) and four
shapes (triangle, star, circle and cross). The participant is re-
quired to match the response card to the stimulus card by one of
three rules (colour, number or shape) but is not told the rule.
They must deduce the correct sorting category based on feed-
back of “correct” or “incorrect”. After four correct matches the
rule changes and the participant must then identify the new
matching rule based on further feedback. Participants who per-
severate would not be able to complete as many shifts as those
who are able to shift quickly. The variable of interest for this
study is total number of shifts.
Simon Task. This task was based on a modified Stroop Task
designed by Hajcak, McDonald & Simons (2003). Much like
the Stroop task, the Simon task requires the respondent to in-
hibit a dominant response. The computer screen presents a se-
ries of red or green arrows oriented left, right or towards the top
of the screen. Participants are directed to respond to the colour
of the arrow by pressing the “j” key for green, and the “f” key
for red requiring them to inhibit responding to the direction of
the arrow. The incongruent trials are expected to incur the
greatest level of errors (i.e. pressing the j key for green, even
though the arrow is pointing left; Hajcak, McDonald & Simons,
2003). There were a total of 200 trials with half congruent and
half incongruent. The key variable of interest for this study is
number of correct responses in the incongruent trials and the
reaction time for these responses. Reaction time for correct
incongruent trials was also recorded.
Procedure
As with study 1, participants were tested in small groups and
were randomly assigned to either a rumination condition or a
distraction condition. They first completed the baseline ques-
tionnaires followed by the induction and then the 3 cognitive
tasks—CPT, WCST and the Simon task. Because the between
group differences were the key comparison, the cognitive meas-
ures were presented in the same order for every participant. As
with the first study, visual analogue scales assessed the partici-
pant’s current mood between the tasks.
Results and Discussion
For this sample, the two experimental groups did not signifi-
cantly differ on age (t = –.104) or baseline measures—RTS (t =
–1.103), PANAS-N (t = –.165) or PANAS-P (t = 1.22). They
also did not differ in their mood rating on the first visual ana-
logue scale prior to the rumination or distraction induction.
Correlations were completed between the baseline measures
and were as predicted (Table 4).
An examination of the change in mood from before and after
the induction shows that prior to induction, the two groups did
not significantly differ (t = –.737) nor following the induction (t
= –1.776, p = .08) although this did approach significance with
those in the rumination condition showing greater negative
mood. To examine the prediction of post-induction mood, a
hierarchical linear regression was completed.
Baseline mood was entered into the first step and induction
condition and RTS score were entered into the second. Both
baseline mood (β = –.235, p = .00) and RTS score (β = –.630, p
= .00) were significant predictors while induction condition was
not.
Hierarchical regressions examined the prediction of conti-
nuous performance scores. As with Study 1, baseline mood was
entered into the first step and RTS and condition in the second.
Results replicate those found in the first study with ruminative
thought style predicting errors of attention in the slow and fast
blocks (Table 5), and baseline negative mood predicting errors
of inhibition in the slow and fast blocks (Table 5). As before,
induction condition was not a significant predictor.
The same statistical procedures were used for the two new
measures of cognitive flexibility, the WCST and the Simon
Task (Table 6). Ruminative thought styles predicted percentage
correct on incongruent trials in the Simon task, and both rumi-
native thought style and baseline mood predicted reaction time
for these trials. Further, both baseline mood and RTS score sig-
nificantly predicted number of shifts in the WCST.
These findings support those obtained in Study 1 without the
limitation of the random assignment anomaly. A ruminative
thought style is related to impairments of attention and negative
mood with impairments in inhibition in the continuous perfor-
mance task. This suggests that for the continuous performance
measure, mood and ruminative thinking are differentially re-
lated to attention and inhibition. However, this becomes less
clear when we consider the findings for the Simon task and the
WCST.
The Simon task was included as a measure of inhibition,
however unlike the CPT, it is the ruminative thought style that
significantly predicts performance on this task, with both mood
and ruminative thought style predicting reaction time. Further,
Table 4.
Baseline correlations.
PANAS-N Mood 1 M SD
RTS .476** –.749** 89.58 19.62
PANAS-N –.539** 21.39 7.21
Mood 1 .599 .193
Note: **p < .01.
228

J. K. BRINKER ET AL.
Table 5.
Predicting cognitive performance by degree of cognitive load control-
ling for baseline mood.
False Hits (Inhibition) Correct Hits (Attention)
High Cognitive Load B SE B B SE B
Step 1
Baseline Mood .060 .010 .480** –.064 .014–.387**
Step 2
Baseline Mood .056 .011 .451** .001 .010.004
RTS Score .003 .004 .062 –.051 .004–.820**
Condition .008 .145 .004 .041 .126.017
Medium Load
Step 1
Baseline Mood –.018 .008 –.213 –.018 .011–.148
Step 2
Baseline Mood –.012 .008 –.142 –.018 .012–.150
RTS Score –.006 .003 –.175 .001 .004.017
Condition –.177 .109 –.142 .134 .154.078
Low Load
Step 1
Baseline Mood .025 .008 .257** –.069 .015–.387**
Step 2
Baseline Mood .018 .009 .191+ .003 .010.020
RTS Score .005 .004 .137 –.056 .004–.850**
Condition .000 .122 .000 .047 .127.018
Note: *p < .05; **p < .01; +p = .055.
both mood and RTS score predict performance on the WCST.
These tasks may draw upon different, if overlapping abilities in
executive function.
General Discussion
As hypothesised, a ruminative thought style predicted cogni-
tive impairments when cognitive load was low, and the combi-
nation of rumination and off-task thoughts surpassed the main
effect in predictive ability. This same relationship was found
when cognitive load was high. When task demands are low,
cognitive resources remain available for intrusive thoughts
which then detract from performance on the task at hand
(Teasdale et al., 1995) but there comes a point where the task
demands become too great, and the influence of ruminative
thought returns (Lybomirsky, Kasri, & Zehm, 2003). This is of
considerable clinical relevance when treating clients with de-
pressed mood and a tendency to ruminate. Depression can lead
to social withdrawal, and isolation to the point where the indi-
vidual may spend days or even weeks with very little external
stimulation (Watson & Andrews, 2002). In this situation, the
cognitive load would be minimal, leaving room for intrusive
ruminative thoughts to thrive. Watson and Andrews (2002)
suggest that this withdrawal and minimization of external dis-
tractions is an adaptive behaviour to help focus the individual
on finding solutions to their stressors. However, this adaptive-
behaviour may become maladaptive when paired with a dispo
Table 6.
Predicting simon and wisconsin card sort task scores.
Simon Task Incongruent B SE B 
Step 1
Baseline Mood –.143 .176 –.073
Step 2
Baseline Mood .171 .191 .087
RTS Score –.263 .071 –.359**
Induction Condition –3.831 2.453 –.135
Simon Task Reaction Time
Step 1
Baseline Mood .519 .813 .057
Step 2
Baseline Mood 1.895 .892 .209*
RTS Score –1.119 .334 –.332**
Induction Condition –9.933 11.470 –.076
WCST Number of Shifts
Step 1
Baseline Mood –.051 .038 –.117
Step 2
Baseline Mood –.121 .042 –.280**
RTS Score .056 .016 .349**
Induction Condition .230 .540 .037
Note: *p < .05; **p < .01.
sition towards a ruminative style of thinking. At the other end,
numerous stressors, may increase cognitive load to a point
where mood and rumination again reduce the ability to inhibit
intrusive thoughts and to maintain attention elsewhere, such as
on problem solving strategies that might otherwise resolve the
stressors.
Koster, De Lissnyder, Derakshan and De Raedt (2011) pro-
pose the impaired disengagement hypothesis and describe a
circular process of stress, ruminative thinking, negative mood,
further ruminative thinking and so on. If one is predisposed to a
ruminative style of thinking, as a result of or concomitant to an
individual difference in executive function, the experience of
this stressor may indeed trigger this maladaptive cycle, espe-
cially if the stressor consumes considerable cognitive resources,
or compels the individual to withdraw thereby eliminating ex-
ternal demands or distracters. In these two situations, the indi-
vidual would not be able to maintain attention elsewhere such
as identifying strengths and resources or on solution generation.
A key consideration in this process is the apparent differen-
tial influences of mood and ruminative thinking. Intuitively,
rumination would seem to be a combination of inability to in-
hibit ruminative thoughts and the inability to maintain attention
elsewhere. However current findings suggest that negative
mood is the phenomenon related to the inability to inhibit and
this has been supported in previous research (Lau et al., 2007).
Rogers et al. (2004) describe mixed results from numerous
studies examining negative mood and executive dysfunction,
but state that most studies have reported deficits in set-shifting.
Much of the previous research has measured set-shifting using

J. K. BRINKER ET AL.
the Wisconsin Card Sorting Task, which does not easily differ-
entiate between the inhibition of previous set and the maintain-
ing of attention on the new set. Executive functions are a com-
plex set of abilities and reside in a number of brain structures
limiting the ability to examine them in isolation (Rogers et al.,
2004). In reality, attempts to differentiate executive functions
may be as artificial as trying to separate depression and rumina-
tion since the interaction between these functions is inevitable.
However, it does suggest that the amelioration of depressed
mood may not necessarily influence the tendency to ruminate,
and this lingering behaviour, may pose a vulnerability to future
depressive episodes.
Finally, it is important to note that the experimental induc-
tions used in these experiments did not produce differences in
mood or cognitive performance and this makes perfect sense
given the theory on which they were created (Lyubomirsky &
Nolen-Hoeksema, 1995; Nolen-Hoeksema, Parker, & Larson,
1994). In the response style theory, individuals ruminate in re-
sponse to existing depressed mood. Asking participants to
spend time focusing on themselves, how they feel and the pos-
sible causes and consequences of those feelings would not pro-
duce consistent outcomes if those individuals are not all ex-
periencing negative mood. Viewing rumination as a style of
thinking is not in conflict with the response style theory, but
simply a different perspective that examines the process of
rumination. New induction procedures that mimic the process
of rumination, independent of content and mood, are needed to
undertake an experimental examination and to establish causal
direction. Current findings show that a ruminative style of
thinking predicts subsequent performance, and it may be that
rumination impairs executive function. However, it seems more
intuitive that structure leads function, and therefore individual
differences in executive function dispose some individuals to a
ruminative style of thinking. Until it is possible to manipulate
one and to observe changes in the other, the causal direction in
this relationship will remain unknown. This area of research has
many more questions than answers, but in time the relationship
between ruminative thinking, executive function and mood will
be clarified and provide further guidance in treating depressed
mood.
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