=Paper=
{{Paper
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|storemode=property
|title=Effects of Emotion and Age on Cognitive Control in a Stroop Task
|pdfUrl=https://ceur-ws.org/Vol-1419/paper0058.pdf
|volume=Vol-1419
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==Effects of Emotion and Age on Cognitive Control in a Stroop Task==
https://ceur-ws.org/Vol-1419/paper0058.pdf
Effects of Emotion and Age on Cognitive Control in a Stroop Task
Natalie Berger (n.berger@bbk.ac.uk)
Department of Psychological Sciences, Birkbeck, University of London, Malet Street
London, WC1E 7HX, UK
Eddy J. Davelaar (e.davelaar@bbk.ac.uk)
Department of Psychological Sciences, Birkbeck, University of London, Malet Street
London, WC1E 7HX, UK
Abstract congruent and incongruent trials relative to ‘neutral’ trials
Research indicates that cognitive control is affected by aging
(non-words such as XXXX printed in different ink colors) is
and by emotion. However, no studies have addressed whether thought to facilitate a shift to proactive control due to high
performance in an emotional Stroop task varies in older expectancy of conflict (e.g., Entel, Tzelgov, Bereby-Meyer,
relative to younger adults. We examined the effect of aging in & Shahar, 2014). In contrast, reducing the amount of
a classic Stroop color-naming task (Experiment 1) and in an congruent and incongruent trials relative to neutral trials is
emotional Stroop task using faces (Experiment 2). Results thought to facilitate a shift away from proactive to reactive
suggest that aging is associated with changes in cognitive control due to low expectancy of conflict. Similarly, trial-
control but that older adults benefit more than younger adults
from positive information in an emotional Stroop paradigm. by-trial changes in control modes can be introduced in cuing
paradigms (e.g., Goldfarb & Henik, 2013). Incongruent
Keywords: cognitive control; emotion; aging; Stroop task trials that are cued are thought to induce shifts to proactive
control in contrast to non-cued items. Studies using the
Background and Motivation Stroop task to test cognitive control usually report longer
The ability to exert cognitive control in the presence of task- RTs for congruent than neutral trials (reversed facilitation)
irrelevant information is crucial for adaptive cognitive and relatively increased RTs for incongruent compared to
functioning in everyday life and has been studied neutral trials (interference) when proactive control is low
extensively in experimental research. A commonly used (e.g., Goldfarb & Henik, 2007).
task to examine cognitive control is the classic Stroop color- Despite a large body of research examining cognitive
naming paradigm (Stroop, 1935). In this task, color words control, studies investigating the effect of aging on different
are printed in congruent or incongruent ink (e.g., “red” control modes are relatively sparse to date. In studies using
printed in red vs green ink) and participants have to name the AX-CPT task, which requires participants to maintain
the color of the ink while ignoring the color word. While goal-related information and to make target responses on
congruent items require the same response for both word cued trials and non-target responses on all other trials, older
reading and color naming, word reading interferes with the adults were found to show significantly impaired goal
correct color-naming response for incongruent trials. Thus, maintenance relative to younger adults (e.g., Haarmann,
incongruent trials are typically associated with slower, less Ashling, Davelaar, & Usher, 2005). These results are
accurate responses than congruent trials (MacLeod, 1991). usually interpreted as evidence for a reduction in proactive
Although the exact mechanisms that enable cognitive control among older adults. However, such results have not
control are still debated, there is reason to believe that been replicated in other experiments (e.g., Paxton, Barch,
cognitive control is not a unitary process. According to the Racine, & Braver, 2008, Exp. 2) suggesting that age-related
dual mechanisms of control (DMC) theory (Braver, Gray, & changes in proactive control are still poorly understood.
Burgess, 2007), cognitive control operates in two distinct Reactive control seems relatively preserved in aging
control modes, ‘proactive control’ and ‘reactive control’. In (Braver, 2012), but brain-imaging data suggest that reactive
their theory, Braver et al. conceptualize proactive control as control is associated with an increase in transient activation
an actively sustained control mode, which is initiated before in older relative to younger adults (Paxton et al., 2008). This
the occurrence of conflict. Thus, proactive control is thought pattern of results was interpreted as evidence that older
to bias attention and action systems in a goal-directed way. adults might perform similar to younger adults by resorting
In contrast, reactive control is activated by the occurrence of to compensatory mechanisms. However, more research is
conflicting events and thus, is only mobilized when needed. needed to understand age-related changes in control modes.
As both control modes are thought to be associated with As the results reported above have been found using the
advantages and limitations (e.g., resource-demanding but AX-CPT paradigm, other tasks may help to shed light on
fast mode of proactive control vs. parsimonious but slow age-related changes in cognitive control.
mode of reactive control), it is suggested that both systems The Stroop task has also been adapted to investigate the
are needed for successful cognitive performance. effects of emotion on cognitive control, often in the context
The Stroop task has also been used to induce shifts in of anxiety or mood disorders. For instance, negative words
control modes. For instance, increasing the amount of (e.g., ‘death’ printed in red) vs neutral words (e.g., ‘desk’
370
printed in red) have been used to investigate interference information, older adults were even more accurate than
caused by emotional content. Generally, participants were younger adults when updating positive information (Mikels,
found to be slower in naming the color of emotional relative Larkin, Reuter-Lorenz, & Carstensen, 2005).
to neutral words (Williams, Mathews, & MacLeod, 1996). Despite evidence of age-related changes in the effects of
A common interpretation is that the affective nature of the emotion on attention, episodic memory and WM, to date, no
emotional words interferes with color-naming by capturing study has examined cognitive control of emotional material
attentional resources (Williams et al., 1996). Similar results in older as compared to younger adults.
were observed for studies using pictures or faces as
emotional stimuli (Kindt & Brosschot, 1997). Although Present studies
some findings suggest that this effect is restricted to We report results of two behavioral studies investigating
negative items (McKenna & Sharma, 1995), other studies proactive and reactive control in aging. The first experiment
have shown that both positive and negative pictures focused on neutral material in the classic Stroop color-
interfered stronger with color-naming than neutral pictures naming paradigm. In the second experiment, we extended
as evidenced in longer RTs (Constantine, McNally, & the task to include emotional material by using facial
Hornig, 2001). In a more recent study, Krug and Carter stimuli. Cognitive control was manipulated by varying the
(2012) reported higher interference by irrelevant emotional amount and thus, expectancy of congruent and incongruent
relative to irrelevant neutral information in a Stroop task. trials relative to neutral trials as in the study of Tzelgov,
This effect was marginally more pronounced under low than Henik, and Berger (1992). High-expectancy (HE) blocks
under high expectancy conditions and thus, when proactive were thought to be associated with increased proactive
control was low. However, as in previous studies emotional control, whilst low-expectancy (LE) blocks were thought to
information was task-irrelevant, it is less clear how task- be associated with reduced proactive control.
relevant emotion would affect performance in a Stroop task. Based on previous research, we expected to find reduced
As suggested by the dual-competition model (DCM; Pessoa, cognitive control in older adults in Experiment 1. In
2009), emotion can improve cognitive performance through Experiment 2, we expected that task-relevant emotion
enhanced target processing. Thus, it is possible that in a would facilitate Stroop performance and reduce age-related
Stroop paradigm, the processing of target emotional differences. It was an open question, whether task-relevant
information can be more resilient against distraction. emotion would interact with expectancy of conflict.
More importantly, no previous study has investigated how
aging affects cognitive control in an emotional Stroop task. Experiment 1
It is important to consider age-related changes when
investigating the interaction between emotion and cognitive Methods
control, as aging is associated with preserved or even
Subjects. Twenty younger (ages 20–40) and 20 older (ages
improved emotional functioning (Charles & Carstensen,
60–85) participated in the experiment. Younger adults were
2010). Older adults seem to place greater importance on
students at Birkbeck, University of London, and received
emotional information compared to younger adults (Fung &
either course credits or £7.50/hour for their participation.
Carstensen, 2003). It was argued that an increased striving
Older adults were high-functioning volunteers, who were
for emotional well-being might underlie age-related changes
recruited from the University of Third Age in London and
in emotional functioning. For instance, socioemotional
were paid £7.50/hour. Participants were community-
selectivity theory (SST; Carstensen, 1993) suggests that
dwelling, pre-screened for psychiatric disorders and a
perceiving time as limited promotes a prioritization of
history of neurological disorders and had normal or
emotional well-being. Consequently, older adults are
corrected-to-normal vision. Subjects were tested
thought to focus more on emotional and particularly on
individually.
positive information, resulting in a ‘positivity bias’ in
Stimuli. Three color words were used in this experiment:
attention and episodic memory (for a review, see Reed &
red, green, yellow. Congruent items were created by
Carstensen, 2012). For instance, it was found that older
printing each of the color names in their own color (e.g.,
adults showed gaze preferences towards positive and away
‘red’ printed in red ink). Incongruent items were created by
from negative stimuli (e.g., Isaacowitz, Wadlinger, Goren,
printing each of the color names in one of the two other
& Wilson, 2006) and that they remembered positive
colors (e.g., ‘red’ printed in green or yellow ink). Neutral
information better than negative information (Charles,
items were created by printing a string of ‘XXXX’ in the
Mather, & Carstensen, 2003).
three different colors. The stimuli were presented centrally
Other studies from the domain of working memory (WM)
on black background in 42-point Courier New font.
have shown that older adults can benefit from task-relevant
Procedure. After giving consent and completing a short
emotional rather than neutral information in cognitive tasks.
visual acuity test, participants were instructed to perform the
For instance, Mammarella and colleagues (2013a; 2013b)
computerized Stroop task. The task consisted of two blocks,
found that older adults showed poorer performance than
and the order of the blocks was counterbalanced across
younger adults in an operation WM span task with neutral
participants. In the HE block, 75% of the trials were either
but not emotional words. In an n-back task with emotional
congruent or incongruent (37.5%, respectively), while 25%
371
of the trials were neutral. In the LE block, 25% of the trials
were either congruent or incongruent (12,5%, respectively)
and 75% of the trials were neutral. Each block consisted of
192 randomly ordered items and the task was preceded by a
practice block of 24 items with an equal amount of
congruent, incongruent and neutral items. Participants were
instructed to indicate the color of the ink as quickly and
accurately as possible by pressing one of three color-labeled
buttons. Button presses initiated the next trials and the
assignment of color labels to buttons was counterbalanced
across participants. Median RTs for correct responses were
analyzed as the main dependent variable in this experiment.
Results and Conclusions
Older adults were generally slower than younger adults,
F(1, 38) = 21.49, MSE = 15280, p < .001. There was also a
main effect of congruency, F(2, 76) = 74.52, MSE = 10480,
p < .001, with significantly longer RTs for incongruent than
congruent or neutral trials. No significant difference was
observed between neutral and congruent trials across both
conditions (p = .880). This main effect was qualified by a
significant congruency × age interaction, F(2, 76) = 8.83,
MSE = 10480, p = .004, as older adults showed a more
pronounced RT difference between incongruent and
congruent or neutral trials than younger adults.
Although there was no main effect of condition (p = Figure 1: RT facilitation and interference in two age
.178), there was a significant condition × age interaction, groups under low-expectancy (LE) and high-expectancy
F(1, 38) = 8.47, MSE = 5091, p = .006, as older adults were (HE) conditions. Error bars represent standard errors.
significantly slower under LE conditions than under HE
conditions. No such effect was observed for younger adults.
Both younger and older adults showed marginally Experiment 2
significant reversed facilitation (RT-congruent vs RT-
neutral) and significantly increased interference under LE to Methods
HE conditions, as revealed by a significant condition ×
Subjects. Twenty-four younger (ages 20–40) and 24 older
congruency interaction, F(2, 76) = 12.66, MSE = 1759, p <
(ages 60–85) participated in the experiment. Both younger
.001. This interaction was qualified by a significant
and older adults were recruited from the same pool of
condition × congruency × age interaction, F(2, 76) = 8.85,
volunteers as in Experiment 1 and met the same criteria.
MSE = 1759, p < .001. This interaction was driven by higher
They were compensated in the same way and none of the
Stroop interference (RT-incongruent vs RT-neutral) in older
subjects, who participated in Experiment 1, were included in
adults, t(19) = 7.01, p < .001, relative to younger adults, p <
Experiment 2. Subjects were tested individually.
.001, t(19) = 3.96, p = .001, in the LE condition (Figure 1).
Stimuli. Stimuli consisted of 36 images of faces from the
Age-related effects were present but less pronounced in the
FACES database (Ebner, Riediger, & Lindenberger, 2010),
HE condition, where again higher interference was shown
a validated set of photographs of naturalistic faces of
by older adults, t(19) = 6.39, p < .001, than by younger
different ages in front view. Faces showed angry, neutral or
adults, t(19) = 4.41, p < .001.
happy expressions (12 items per emotion). Faces were
This pattern of results suggests that similarly to young
selected in a way that age group (young, middle-aged, older)
adults, older adults exhibited proactive control under HE
and sex (male, female) of the face models were balanced
conditions, as evidenced by facilitation and reduced
equally in each emotion category. The faces had been rated
interference in both age groups. Notwithstanding, aging was
in a preliminary evaluation study and were selected based
associated with changes in cognitive control as evidenced
on high agreement ratings between younger and older raters.
by an age-related increase in interference. Moreover, age-
Angry, neutral and happy faces varied significantly in
effects were more pronounced under LE conditions und
their valence and angry and happy faces were matched for
thus, when proactive control was low. Incongruent trials
arousal. Congruent items were created by printing matching
caused disproportionately longer RTs relative to neutral
emotion labels across the emotional faces (e.g., happy face
trials in older than in younger adults. This indicates that
with ‘happy’ label). Incongruent items were created by
Stroop-interference is affected by aging and interacts with
printing non-matching emotion labels across the faces (e.g.,
available levels of control.
happy face with ‘angry’ label). Neutral items were created
372
by printing a string of ‘XXXX’ across the faces. Face
pictures were turned to grey-scale, whilst labels were
printed in red, 38-point Courier New font, and placed
between eyes and mouths of the faces. To facilitate label
reading, labels appeared 100 ms before the face.
Procedure. After giving consent and completing a short
visual acuity test, participants were instructed to perform the
computerized emotional Stroop task. The task consisted of
two blocks and the proportion of congruent, incongruent
and neutral in the HE block and in the LE was identical as in
Experiment 1. Each block consisted of 288 randomly
ordered items and the task was preceded by a practice block
of 24 items with an equal amount of congruent, incongruent
and neutral items. Participants were instructed to indicate
the emotion of the face irrespective of the label as quickly
and accurately as possible by pressing one of three labeled
buttons (‘A’ for angry, ‘N’ for neutral, and ‘H’ for happy).
A button press initiated the next trial and the assignment of Figure 2: RTs for emotional stimuli in two age groups
labels to buttons was counterbalanced across participants. across items and conditions. Error bars represent standard
Median RTs for correct responses were analyzed as the errors.
main dependent variable in this experiment.
Results and Conclusions General Discussion
Older adults were generally slower than younger adults, The aim of the present research was to investigate how
F(1, 46) = 20.03, MSE = 472052, p < .001. A main effect of emotion and aging affect cognitive control in a Stroop task.
congruency, F(2, 92) = 42.24, MSE = 21342, p < .001, was Data from Experiment 1 show that older adults can deploy
observed as RTs were faster for congruent than neutral proactive control in the face of varying task demand. This
items and faster for neutral than for incongruent items. Both was evidenced by facilitation and reduced interference in
younger and older adults showed increased interference the HE relative to the LE block. However, cognitive control
under LE relative to HE conditions, as evidenced by a was found to be affected by aging in both conditions: Older
significant condition × congruency interaction, F(2, 92) = adults showed increased interference from incongruent trials
4.73, MSE = 6897, p = .019. Facilitation was unaffected by relative to younger adults. More pronounced age-related
condition. No further effects including the factor condition changes were observed when proactive control was low, as
were observed. Emotion significantly affected RTs, F(2, 92) interference in older relative to younger adults was more
= 21.17, MSE = 48104, p < .001, as all participants were increased under LE compared to HE conditions.
faster for happy than neutral or angry faces. No significant Data from Experiment 2 suggest that emotion affects
difference was found between angry and neutral faces (p > performance in a Stroop task irrespective of expectancy
.05). However, this main effect was qualified by a manipulations and thus, task demands. It was found that
significant emotion × age interaction, F(2, 76) = 3.95, MSE both age groups were fastest when responding to happy
= 48104, p = .04. This interaction was driven by a more faces rather than neutral or angry faces. However, this effect
pronounced RT advantage for happy faces relative to neutral was more pronounced for older adults as they showed a
and angry faces in older as compared to younger adults higher speed advantage for happy faces than younger adults.
(Figure 2). This facilitating effect of task-relevant positive emotion was
These findings suggest that emotion modulated RTs observed across congruent, incongruent and neutral items.
irrespective of item congruency or expectancy of conflict. In Both experiments shed light on age-related changes in
the presence of emotional material, interference was cognitive control in the presence of neutral and emotional
increased under LE conditions relative to HE conditions in material. The findings add to the empirical evidence
both younger and older adults, with no effects of conflict obtained in studies using the AX-CPT paradigm. Our results
expectation observed for facilitation. Happy faces were are compatible with studies showing impairments in goal
associated with fastest RTs compared with neutral or angry maintenance in older adults, which were interpreted as an
faces in both age groups. However, it was found that this age-related reduction in proactive control (Haarmann et al.,
RT advantage for happy faces was more pronounced for 2005). Under HE conditions, older adults showed increased
older than for younger adults. These results suggest that interference from incongruent trials relative to younger
older adults benefit from positive information as conveyed adults. This might indicate that active maintenance of task
by smiling faces to a greater extent than younger adults do. goals was reduced in older adults, resulting in higher
conflict experienced for incongruent stimuli. Moreover, our
results extend previous findings by showing that word-
373
reading interfered stronger with color naming in older than These changes to the original Stroop task might have
in younger adults when proactive control was low: older contributed to the discrepancy in results between the two
adults were disproportionately slower than younger adults experiments. Faces rather than words were used as they are
when responding to incongruent relative to neutral items ecologically valid emotional stimuli, whereas words convey
under LE conditions. Given the implication by the dual emotional meaning in a symbolic way. A comparison of
mechanisms of control (DMC) theory that a shift away from stimulus types indeed showed stronger effects of valence for
proactive control facilitates the use of reactive control pictorial stimuli than for words (Kensinger & Schacter,
(Braver et al., 2007), our results suggest that reactive control 2006). Also, it was suggested that even with word stimuli,
might also be affected by aging. Previous studies have emotional Stroop tasks differ from the Stroop color-naming
shown that reactive control is largely preserved in older task for a number of reasons (Algom, Chajut, & Lev, 2004).
adults (Braver, 2012), but there is also evidence that older For instance, it was argued that the Stroop effect cannot be
adults’ reactive control is less efficient, as compensatory calculated in an emotional Stroop as no “true” consistency
mechanisms might be recruited at neural levels (Paxton et exists for non-color words printed in different colors. Thus,
al., 2008). Our results are in line with those pointing at less the inclusion of stimuli other than color words comes with
efficient reactive control in older relative to younger adults. major methodological changes, independently of stimulus
Finally, the finding of increased interference in older adults type.
is consistent with findings of reduced inhibition of irrelevant To conclude, our studies extend previous research by
information with aging (e.g., Hasher, Stoltzfus, Zacks, & showing that age-related changes were more pronounced in
Rypma, 1991). a Stroop task when proactive control was low. Furthermore,
The results from Experiment 2 suggest that emotion it was shown that performance in an emotional Stroop task
affects Stroop performance irrespective of expectancy was affected by aging and by emotion. More specifically,
across all trial types. Both age groups were fastest when older adults were disproportionately faster when responding
responding to happy faces, but this RT advantage was more to happy rather than angry or neutral faces compared to
pronounced in older than in younger adults. The speed-up in younger adults. Further research is needed to clarify whether
responses for happy faces is in line with research showing this happy face advantage was driven by perceptual or
that happy expressions are processed quicker and more conceptual features of the stimuli. By furthering our
accurately relative to other facial expressions (Becker & understanding of the effects of emotion on cognitive control
Srinivasan, 2014). However, a purely perceptual account of in aging, such work can help identifying situations in which
our results would imply that older adults are faster or better older adults’ cognitive performance can be facilitated
in recognizing happy faces than younger adults, which is not through emotion.
supported by research (for a meta-analysis, see Ruffman,
Henry, Livingstone, & Phillips, 2008). In contrast, a more Acknowledgments
pronounced RT advantage for happy faces in older relative This work was supported by Birkbeck, University of
to younger adults is more consistent with a conceptual view London.
of emotional changes in aging and findings showing a
‘positivity bias’ in attention and memory in aging (Reed &
Carstensen, 2012). It is possible that the emotion × age
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