1. Running head: EXECUTIVE CONTROL IN MONOLINGUALS AND BILINGUALS
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! ! Potential Effects of Bilingualism on Executive Control!
Marcella Lovo!
Bowdoin College!
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! ! ! ! ! ! Author Notes!
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Marcella K. Lovo, Department of Psychology, Bowdoin College. The author wishes to
thank Louisa Slowiaczek for feedback on an earlier version of the manuscript, as well as
research partners, Emma Stanislawski and Autumn Nelor for their support and
collaboration. Correspondence concerning this article should be addressed to Marcella
K. Lovo, 17 Cleaveland Street, Brunswick, ME 04011. E-mail: mlovo@bowdoin.edu. !
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2. Running head: EXECUTIVE CONTROL IN MONOLINGUALS AND BILINGUALS
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Abstract!
! A potential bilingual advantage on executive control was examined in the present
experiment. Monolingual and Bilingual subjects had to manipulate a set of discs
separated by pegs of different heights presented in an original state to match a goal
state. The difficulty of the task increased as the number of moves required to solve the
problem increased. Subjects were the fastest and most accurate at responding to tasks
that required the least amount of moves; and inversely were slowest and least accurate
at responding to tasks that required the most amount of moves. The results did not
support past findings of a bilingual advantage, and suggest that more attention should
be focused on defining the limitations of the present experiment in order to find a
potential bilingual advantage in future replications of the study.!
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3. Running head: EXECUTIVE CONTROL IN MONOLINGUALS AND BILINGUALS
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Potential Effects of Bilingualism on Executive Control!
! ! Past literature has shown consistent findings that bilinguals outperform
monolinguals in tests that measure executive control (i.e., the control of thought and
action) such as tests of inhibitory function, flanker paradigms, and Stroop tests,
therefore implying a bilingual advantage on executive control. Cognitive processes that
include the control of thought and action include the coordination of habit and skills,
monitoring and correcting performance, making choices among tasks, and planning
future actions. Other experimenters have extended their findings of a bilingual
advantage on executive control to potentially find a bilingual advantage on tests that
assess for creativity. Divergent explanations have attempted to define the potential
effects of a bilingual advantage. One popular theory among researchers suggests that
the the regular use of two languages requires a mechanism to control attention in order
to select the target language--an experience that may enhance executive control. !
! Researchers Emmorey, Pyers, Luk, and Bialystok (2008) examined the source of
the enhanced cognitive control in bilinguals by manipulating a set of flanker tasks
counterbalanced across subjects. Emmorey et al. (2008) expected to find significant
differences between subjects who spoke two spoken languages compared to
monolinguals and participants who spoke a sign and a spoken language.The
researchers predicted that the bilingual advantage stems from a mechanism that forces
language selection acquired from the same modality and not from different modalities
(Emmorey et al, 2008). Researchers selected bimodal bilinguals (i.e., speak sign and
spoken language), unimodal bilinguals (i.e., speak two spoken languages), and
4. Running head: EXECUTIVE CONTROL IN MONOLINGUALS AND BILINGUALS
unimodal monolinguals (i.e., speak one spoken language) to participate in a study
where subjects were told to indicate the direction of a visually presented image of a red
chevron flanked in four different conditions. Participants were told to either give or
withhold their response (i.e., go/no-go condition), or presented with flankers that pointed
in the same direction as the chevron or the opposite direction (i.e., congruent/
incongruent). The results of the study revealed that unimodal bilinguals in both the go/
no-go trials and congruent/incongruent trials responded faster than the other groups,
who did not differ from each other, suggesting that the bilingual advantage for executive
control arises from acquiring two languages in the same modality and not simply from
being bilingual (Emmorey et al., 2008). The higher performance of unimodal bilinguals
on Emmorey et al.’s (2008) flanker tests demonstrates that the bilingual advantage is
not simply found in tasks that measure an increase in inhibitory control, but may also be
found in other aspects of executive control that the flanker tests assessed, such as
attentional mechanisms, monitoring, and task switching processes. !! !
Researchers Prior and Gollan (2011) explored the the different types of bilinguals in
non-linguistic task switching and language switching paradigms counterbalanced across
participants. Prior and Gollan (2011) expected to find a bilingual advantage on general
task-switching abilities for Spanish-English bilinguals, who reported switching languages
more frequently than Mandarin-English bilinguals. The researchers predicted that there
would be a positive correlation between the frequency of language switching and a
subjects’ performance scores on paradigms. In the non-linguistic task-switching
paradigm, both monolingual and bilingual participants were cued by either a color
gradient or a group of small shapes to make color and shape judgements on visually
5. Running head: EXECUTIVE CONTROL IN MONOLINGUALS AND BILINGUALS
presented stimuli, using the right hand to perform one task and the left hand for the
other. Only Bilingual subjects were cued by a language’s associated flag (i.e., Mexican
flag for spanish, American flag for english, and Chinese flag for Mandarin) to read the
visually presented single digits (1-9) in the cued language aloud for the language
switching paradigm. Bilingual subjects were instructed to either repeat saying the
number aloud in the cued language or to switch the language spoken in the linguistic
task; whereas, monolinguals and bilinguals were instructed to either repeat or switch the
hand used to make the color/shape judgements in the non linguistic task. ! ! !
! Results revealed that after controlling for between group differences in parental
education level, Spanish-English bilinguals were faster than Mandarin-English bilinguals
at switching the language used in the linguistic task and were also the fastest at
switching the hand used in the non-linguistic task. The findings suggest that Spanish–
English bilinguals might demonstrate more efficient task-switching skills compared to
monolinguals because they routinely switch languages, and suggest that Spanish-
English bilinguals are more efficient than Mandarin-English bilinguals because they
reported switching more frequently than the other bilingual group. (Prior & Gollan,
2011). Furthermore, the results demonstrate that specific aspects of bilingualism rather
than a general effect--in this case being the frequency of language switching, is
correlated to better performance on measures of executive control such as task
switching. Aside from executive control tasks, however, a bilingual advantage can be
found in other cognitive processes such as creativity. !
! A.V. Karhkhurin (2009) investigated the possible influences of bilingualism on an
individual’s creative potential by using a set of tests that evaluated both generative
6. Running head: EXECUTIVE CONTROL IN MONOLINGUALS AND BILINGUALS
capacity (i.e., the ability to activate a multitude of unrelated concepts and work through
concepts already activated) and innovative capacity (i.e., the ability to produce
innovative and useful ideas). Kharkurin (2009) defined both innovative and generative
capacity as aspects of divergent thinking (i.e., involves a broad search of information
and the generation of numerous novel alternative answers/solutions to a problem).
Researchers selected a group of Farsi-English speaking bilingual subjects and Farsi
monolingual subjects and instructed them to imagine, draw, and describe an alien like
creature on a drawing task named the Invented Alien Creature Task (IAC) . A separate
group of participants were asked to judge the creativity for each drawing and to rate
them (1-6). After the creativity scores were evaluated, independent research assistants
(both fluent farsi and english speakers) then had to measure how far the representation
deviated from a conventional human prototype. Using the study’s invariant coding
system, assistants analyzed the symmetry as well as the number of eyes and limbs of
each alien drawing. A value was assigned to each of the five categories within each
invariant (e.g., for the invariant “symmetry”, one of the categories was “not bilaterally
symmetrical”(2)), and assistants added the values to calculate the total invariant score.
The invariant score indicated how far the drawing deviated from the standard human
image. The researchers’ invariant score was expected to to positively correlate with the
participants’ creativity ratings. ! ! ! ! ! !
! The results did show a significant correlation between the creativity ratings and
the invariant score, and demonstrates that subjects judged the alien drawings which
deviated the most from the accepted human image as the most innovative. Interestingly
enough, Bilinguals had higher invariant scores and creativity ratings than monolinguals,
7. Running head: EXECUTIVE CONTROL IN MONOLINGUALS AND BILINGUALS
suggesting that bilinguals exhibit greater innovative capacity than monolinguals
(Kharkurin,2009). !
! In the second half of the experiment, researchers measured divergent thinking
ability using a written test (i.e., ATTA) that instructed participants to use their imagination
on three open ended activities. For example, in one activity, the respondent is given a
“just suppose” prompt and then asked to list problems that might arise. The results from
the ATTA test confirmed the significant differences between bilinguals and monolinguals
found in the IAC for innovative capacity, however, the results contradicted past findings
that demonstrated better performance among bilinguals for generative capacity
(Kharkurin, 2009).! ! ! ! ! ! ! ! ! !
Kharkurin’s (2009) study acknowledged the number of different uncontrolled
sociocultural factors that potentially could explicate the contradiction, such as
intelligence and socioeconomic status, as well as the divergent cultural values and
comprising meanings and schemas between monolinguals and bilinguals that construct
an individual’s subjective creativity. Kharkurin’s (2009) study provides sound
explanations of the limitations in his study, which can be applied to other studies aimed
at exploring the effects of bilingualism and at finding a potential bilingual advantage. !
The aim of the present study is to recreate previous findings regarding the bilingual
advantage in executive control through the Tower of London task. The Tower of London
is a spatial problem solving task that assesses executive control, specifically regarding
planning and problem abilities. Bilinguals should be more accurate and faster to
respond than monolinguals at every level of task difficulty because of their bilingual
advantage.!
8. Running head: EXECUTIVE CONTROL IN MONOLINGUALS AND BILINGUALS
! ! ! Method!
Participants!
! Twenty undergraduate students from Bowdoin College participated in the present
experiment to fulfill a course requirement. Half of the participants were bilingual, while
the other half were monolinguals. All participants had normal/corrected to normal vision.!
Materials!
! The stimuli included three different color discs (i.e., red, blue, green) and three
different sized pegs (i.e., small, medium, large) presented in an original and goal state.
Only one disk could fit in the smallest pig, two disks could fit in the medium sized peg,
and three disks could fit in the largest peg. The experiment was controlled by
Psychmate software (St. James, Schneider & Eschman, 2005). Participants were tested
on Dual Boot Macintosh computers on windows operating systems. Participants
responded using computer keyboards. !
Procedure!
Participants were presented a starting state and a goal state. Their task was to
manipulate the disks to duplicate the goal state. The disks varied in color (i.e., red, blue,
green), the pegs varied in height (i.e., small, medium, large) and the number of moves
required to solve the problem correctly varied in difficulty (i.e. four, five, six). Thirty trials
were presented, with an equal number of the difficulty levels (10). Presentation of the
conditions were randomized within participants. Subjects completed each of the 30
experimental trials given a two minute maximum response time before it was replaced
with the following trial.! ! ! ! ! ! ! !
9. Running head: EXECUTIVE CONTROL IN MONOLINGUALS AND BILINGUALS
! Each trial began with two rectangles at the top of the screen. The rectangles
displayed three pegs of different heights and three disks. The starting position was
displayed on the left side, while the goal state was displayed on the right side. Subjects
manipulated the disks at the starting position to duplicate the goal state by selecting a
disk and then clicking on the intended peg. For each trial, participants were told the
number of moves required to solve the problem correctly. Feed back was presented
after each trial in the form of cumulative accuracy as well as response time. Feedback
for correct responses was printed in blue and for incorrect responses were printed in
red. !
Design !
The present study was a 2 x 3 mixed design. Language type was manipulated between
subjects such that half of the subjects selected were monolinguals and the other half
were bilinguals. The level of difficulty was manipulated within subjects such that tasks
either required four, five, or six moves to come to a solution. !
Results!
! The mean number of correct responses as well as mean response time was
determined for the 18 subjects for the three levels of difficulty by two levels of language
type. Two scores that were reported below .20 were removed from the present study,
and two dummy variables that averaged across the conditions for the two subjects
replaced the missing values. The mean percent correct accuracy and response time
scores across subjects for each level of difficulty and language type are provided in
Table 1. !
! Two 2 x 3 Analyses of Variance (ANOVA) were conducted across the two levels
of language type and three levels of difficulty for both the response time and accuracy
10. Running head: EXECUTIVE CONTROL IN MONOLINGUALS AND BILINGUALS
data. Results did not reveal a main effect of language type, F(1,18)=.047,
MSe=289612914.3, p>.831 or an interaction, F(2,36)=.093, MSe=88539247.04 p>.912
for response time. Bilinguals (M=30403ms) were no faster than monolinguals
(M=31353ms) in any of the the levels of task difficulty.!
! Results did reveal a main effect of difficulty for response time, F(2,36)= 19.30,
MSe=88539247.04, p<.05. Follow up t-tests revealed significant differences between
trials that involved four (21407ms) and five (31350ms) moves, t(19)=-4.57, SE=2173.69,
between four (21407ms) and six moves (39877ms), t(19)=-5.36, SE=3445.74, and
between five (31350ms) and six moves (39877ms), t(19)=-2.89, SE=13187.48. These
findings reveal that when the task required more moves, participants were slower to
respond. !
! Results did not reveal a main effect of language type, F(1,18)=1.86, MSe=.070,
p>.05, or of an interaction, F(2,36)=1.04, MSe=.018, p>.05 for accuracy. Bilinguals (.81)
were not more accurate than monolinguals (.72) for any level of task difficulty.!
! A main effect of move was found for accuracy F(2,36)=7.18, MSe=.018, p<.05.
Follow up t-tests revealed significant differences between four (.85) and six moves
(.69), t(19)=4.56, SE=.053, p<.05, but no differences between four (.85) and five moves
(.76), t(19)-1.69, SE=05, p>.107, or between five (.76) and six moves t(19)=1.93,
SE=.04, p>.05. These findings reveal that participants were less accurate when the task
required five and six moves but only when compared to when it required four moves. !
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11. Running head: EXECUTIVE CONTROL IN MONOLINGUALS AND BILINGUALS
Discussion!
! A bilingual advantage was not found in the present experiment because there
were no significant differences of language type between bilingual and monolingual
participants for both accuracy and response time data. As predicted, an interaction
between the level of difficulty and language was not found in the experiment. Significant
differences were found, however, for the tower of London task for both response time
and accuracy data, revealing that participants were slower to respond when the trials
increased in difficulty (i.e., required more moves). !
! While significance was not found for language type between subjects, the
significant differences found for the task demonstrate that that the Tower of London is
an effective test for measuring a potential bilingual advantage between monolinguals
and bilinguals. Responses were the fastest and the most accurate for tasks that
required the least number of moves (i.e., four moves) and the slowest for tasks that
required the greatest number of moves (i.e., six moves). !
! Response time to any given trial was a function of planning and execution time.
Participants were slowest to respond to the trials that required six moves because the
task involved more extensive planning strategies, which therefore resulted in more time
needed to solve the problem. Inversely, subjects were the fastest in tasks that required
the least number of moves because less time was needed to strategize for a problem
that requires four moves in comparison with six moves. It was easier for subjects to
control their pre planning strategy and resulting action when the task was less
sophisticated. !
12. Running head: EXECUTIVE CONTROL IN MONOLINGUALS AND BILINGUALS
! Despite the present study’s lack of statistically significant findings, past literature
has found a bilingual advantage for executive control processes such as on attentional
mechanisms and task switching as well as for creativity. Emmorey, Luk, Pyers, and
Bialystok (2008) investigated the different modalities of bilingualism by testing on both
sign and spoken language speakers and only found a bilingual advantage for unimodal
bilinguals (i.e., subjects who spoke two spoken languages), suggesting that the bilingual
advantage on executive control stems from having to monitor and control for two
languages of the same modality. Similar to Emmorey et al.’s (2008) investigative
approach on bilingualism, Prior and Gollan (2011) explored the differences between
Spanish-English and Mandarin-English bilinguals on a task-switching paradigms and
expected to find a bilingual advantage for Spanish-English bilinguals because the
subjects reported switching languages more frequently the Mandarin-English bilinguals.
Prior and Gollan’s (2011) as well as Emmorey et al’s (2008) findings suggest that a
bilingual advantage can be attributed to specific aspects of bilingualism rather than a
general effect of bilingualism. ! ! ! ! ! !
! Aside from processes of executive control, a bilingual advantage has been found
on other cognitive processes such as an individual’s creative potential. Karkurin (2009)
used imaginative alien drawing (e.g., IAC) tasks and a test that measured divergent
thinking (e.g., ATTA) on Farsi monolingual and Farsi-English bilingual subjects to assess
for levels of creativity. The results of the study suggest that bilinguals exhibited greater
innovative capacity (i.e., the ability to produce novel ideas); however, the findings
conflicted with past literature that found a bilingual advantage for generative capacity
(i.e., ability to activate a multitude of unrelated concepts). Kharkurin (2009) provided
13. Running head: EXECUTIVE CONTROL IN MONOLINGUALS AND BILINGUALS
insightful explanations of the contradiction by taking into account the variances of
economic status, intelligence, and divergent cultural values between monolinguals and
bilinguals. The uncontrolled sociocultural factors that were underlined in Kharkurin’s
(2009) study can be applied to the present study’s contradictory findings with past
literature. Underlying limitations such as those defined in Kharkurin’s (2009) study
prevented the present experiment from revealing a potential bilingual advantage on
executive control. !
! In future replications of the experiment, a bilingual advantage can potentially be
found by, for example doubling the number of subjects to twenty bilinguals and twenty
monolinguals. The increase in participants will increase the power of the test, and thus it
will be easier to detect the differences in response time and accuracy scores between
monolinguals and bilinguals. Another limitation of the study is that the software did not
distinguish between preplanning time and execution time. Given that executive control
is linked to processes that involve coordinating thought and action, the pre planning
time alone, required to strategize before the execution of the strategy, would have been
a more effective measure of executive control than combining both the preplanning and
execution times. Had the experiment distinguished between the two times, it is expected
that bilinguals would take less time strategizing and execute more accurately than the
monolinguals. Since bilinguals have to constantly inhibit one language in order to select
the target language, they are more experienced with monitoring their thoughts and
actions and therefore would hypothetically be faster at preplanning than monolinguals.!
14. Running head: EXECUTIVE CONTROL IN MONOLINGUALS AND BILINGUALS
! A bilingual advantage on either executive control or creativity has been
suggested and cited in past literature, which reminds experimenters to assess the
potential of their experiment rather than solely the raw data. !
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15. Running head: EXECUTIVE CONTROL IN MONOLINGUALS AND BILINGUALS
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References!
Emmorey, K., Luk, G., Pyers, J.E., & Bialystok, E. (2008). Psychological Science. The !
Source of Enhanced Cognitive Control in Bilinguals, 19, 1201-1206. !
Kharkhurin, A.V. (2009). Journal of Creative Behavior. The Role of Bilingualism in !
Creative Performance on Divergent Thinking and Invented Alien Creature Tests, ! 43,
59-71. !
Prior, A. and Gollan, T.H. (2011). Journal of the International Neuropsychological !
Society. Good Language-Switchers are Good Task-Switchers: Evidence from !
Spanish-Engilsh and Mandarin-English Bilinguals, 17, 682-691.!
St. James, J.D., Schneider, W., & Eschman, A. (2005). PsychMate: Experiments for
Teaching Psychology, Student Guide v. 2.0, Psychology Software Tools, Inc.
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