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J Int Neuropsychol Soc. 2014 March ; 20(3): 342–348. doi:10.1017/S1355617714000058.

Second-Language Fluency Predicts Native Language Stroop

Effects: Evidence from Spanish–English Bilinguals
Paola A. Suarez1,2,4, Tamar H. Gollan2, Robert Heaton1,2,4, Igor Grant2,3,4, Mariana
Cherner1,2,4, and HNRC Group4
1San Diego State University/University of California San Diego Joint Doctoral Program in Clinical
Psychology, San Diego, California
2Department of Psychiatry, University of California San Diego, La Jolla, California
3VA San Diego Healthcare System, San Diego, California
4HIV Neurobehavioral Research Center, University of California San Diego, San Diego, California
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Abstract
Studies have shown reduced Stroop interference in bilinguals compared to monolinguals defined
dichotomously, but no study has explored how varying degrees of second language fluency, might
affect linguistic inhibitory control in the first language. We examined effects of relative English
fluency on the ability to inhibit the automatic reading response on the Golden version of the
Stroop Test administered in Spanish. Participants were 141 (49% male) adult native Spanish
speakers from the U.S.–Mexico border region (education range =8–20 and age range =20–63). A
language dominance index was calculated as the ratio of English words to total words produced in
both languages using the Controlled Oral Word Association Test with letters PMR in Spanish and
FAS in English. Greater degree of English fluency as measured by the dominance index predicted
better speed on the Stroop incongruent trial independent of education effects. On the other hand,
neither the dominance index nor education predicted performance on the word reading and color-
naming trials. These results suggest an advantage in inhibitory control among those with greater
second-language ability.
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Keywords
Bilingualism; Hispanic Americans/psychology; Executive function; Verbal fluency; Regression
analysis; Educational status; Spanish speaker

INTRODUCTION
Studies emanating primarily from the cognitive science literature suggest both advantages
and disadvantages of bilingualism for cognitive performance. According to the Inhibitory

Copyright © INS. Published by Cambridge University Press, 2014.

Correspondence and reprint requests to: Paola Suarez, Department of Psychiatry, University of California San Diego, 9500 Gilman
Drive, La Jolla, CA 92093-0847. pasuarez@ucsd.edu.
The authors have no conflict of interest.
 Suarez et al. Page 2

Control Model, bilinguals must suppress the non-target language to allow production of the
intended language (Green, 1998). This constant experience with linguistic conflict resolution
can be seen as practice of executive and attentional control, thus predicting a bilingual
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advantage on tasks requiring these abilities. While most of the work in bilingual
neurocognition has been conducted using experimental paradigms, often with college
students, translation into clinical applications for linguistically diverse groups requires
understanding how these performance predictions hold when using tests that are commonly
administered in clinical settings and with a broader demographic representation. Given that
Spanish speakers in the United States vary in their English proficiency, it is important to
understand how this second language ability affects neuropsychological (NP) performance
in the first language. This has implications for the interpretation of test results when
diagnosing brain dysfunction in bilingual patients, as bilingualism may affect NP test
performance beyond what would be predicted by normative corrections for age, education,
sex and ethnicity. To this end, the current study examined the effects of English fluency on
performance in Spanish on a test that measures executive and attentional functioning.

In support of the Inhibitory Control Model (Green, 1998), research (Bialystok, 2001, 2010,
Bialystok & Viswanathan, 2009, Carlson & Meltzoff, 2008) has shown bilingual advantages
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in young children on tasks measuring selective attention and inhibition. When tested in a
language in which they are proficient, bilingual advantages can also be demonstrated in
adults, particularly on tasks measuring inhibition of an unwanted response (e.g., flanker task
and Simon task). For example, Bialystok, Craik, and Luk (2008) showed that bilinguals who
learned English as a second language but were considered proficient in English (with a
variety of languages as their first language), showed smaller Stroop interference effects,
compared to matched monolingual English speakers. This effect was particularly prominent
in older bilinguals, who also displayed more facilitation (i.e., words printed in their own
color relative to neutral condition) and less costs (i.e., incongruent condition relative to
neutral condition), relative to older monolinguals. These effects remained robust after
controlling for the effects of aging on speed of information processing, suggesting that
bilingualism may attenuate the expected age-related decline in certain executive functions.

Tzelgov, Henik, and Liser (1990) documented robust proficiency effects in a bilingual
Stroop task as measured by reaction time differences between the congruent and incongruent
trial, considering both within and between language Stroop effects in Hebrew–Arabic
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bilinguals. Relatively balanced bilinguals exhibited Stroop interference within-languages

and between languages, but Stroop effects were larger within- than between-languages. In
contrast, for unbalanced bilinguals, Stroop effects (both within- and between-languages)
tended to be smaller when the stimulus language (i.e., reading) was not their native
language. In addition, Tzelgov and colleagues showed that the size of the Stroop effect was
modulated by second language proficiency such that some minimum proficiency level is
required for interference effects to emerge, but at higher levels of proficiency, bilinguals
also become better at controlling target language activation.

By contrast, some studies examining the differences on the Stroop task between bilingual
and monolingual groups have failed to find a bilingual advantage. For example, the Stroop
Color–Word incongruent trial was administered in both English and Spanish at separate

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times to a sample of 36 cognitively intact Hispanic American bilingual adults who were
classified as either English-dominant, balanced bilinguals, or Spanish-dominant (Gasquoine,
Croyle, Cavazos-Gonzalez, & Sandoval, 2007). The main aim of this study was to examine
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differences in neuropsychological performance according to language dominance and

language of test administration (English vs. Spanish). Among balanced bilinguals, no main
effect of language of administration was found on the Color–Word incongruent trial as
measured by number of colors named in 45 s. While this study made no direct comparisons
between balanced bilinguals and Spanish-dominant participants, calculation of an effect size
with the data provided yielded only a small effect (Cohen’s d =0.22). On average, Spanish-
dominant participants were able to name two more colors on the Spanish Stroop incongruent
condition than did the bilingual participants.

Along the same lines, Rosselli et al. (2002) examined the Stroop effect in Spanish-English
bilinguals who were tested in both English and Spanish on the Word Reading and Color
Naming conditions, and an inter-language condition (e.g., word written in English and asked
to name color in Spanish) for the Color–Word incongruent trial. Spanish and English
monolingual groups were also tested with the Stroop administered only in their native
language. The outcome variable was the number of correct words named in 45 s.
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Comparisons between the bilingual and monolingual participants were made using the
monolinguals’ language as the stimuli language for the bilingual group (e.g., performance of
monolingual Spanish speakers vs. performance of bilinguals on the Spanish version). The
results showed no bilingual advantage or disadvantage on the incongruent condition. While
bilinguals were significantly slower than the monolinguals by approximately 10 to 15% in
the English Color Naming condition, they performed comparably on the incongruent trial,
performing only 5 to 10% slower, based on time to complete the task, when compared to
monolinguals. Thus, bilinguals may have exhibited somewhat better ability to manage
interference in this study (given their relatively better performance on the incongruent trial
than expected based on their slow Color Naming times). However, as noted by Rosselli and
colleagues, their failure to find significant differences between the bilingual and
monolingual groups could have resulted from a small number of Spanish monolinguals
tested (n =11), and a larger sample may have yielded different results.

While bilingual effects on inhibitory and attentional control are increasingly well
documented in controlled experimental settings, it remains to be understood how these
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findings apply to natural populations with varying degrees of second language fluency, such
as might be the case with immigrant groups in the United States. It is important to note that
in the existing literature, bilingualism has been treated as a dichotomous variable, and
research has been conducted primarily with college age students along with a few studies
with elderly populations and children. Thus, the present study addresses gaps in the
literature by examining effects of second language fluency on Stroop performance in the
first language in a sample with a range of age and education that is presumably more
representative of the general population. In addition, relative English fluency will be treated
as a continuous variable, which is a closer reflection of the state of second language fluency
that would be encountered in typical clinical situations in the United States.

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Spanish-speakers in the United States vary in degree of English proficiency. However, it is

not well understood whether levels of English proficiency affect test performance in native
Spanish speakers who prefer to be evaluated in Spanish. To examine the effects of English
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proficiency when Spanish speakers are performing in their native language, we developed an
index based on measures of phonemic fluency in each language (i.e., English letter fluency,
FAS; and Spanish letter fluency, PMR). A dominance index was calculated as the number of
total words produced in English compared to total words uttered in both English and
Spanish. This index makes it possible to examine second language fluency in relation to first
language fluency as a continuous variable, as opposed to quantifying persons as strictly
bilingual or monolingual, balanced or unbalanced. Moreover, treating relative English
fluency as a continuous variable provides a potential way of adjusting neuropsychological
test scores for this variable when assessing Spanish speakers. We hypothesized that greater
relative English fluency among native Spanish speakers would be associated with a smaller
Stroop effect on the Golden version of the Stroop Test administered in Spanish. More
specifically, greater second language fluency would be associated with better ability to
inhibit the automatic reading response in the native language on the Color–Word
incongruent trial as measured by a speed score. Since demographic variables (i.e., years of
education, sex, and age) have been found to predict performance on the Stroop Test (Artiola
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i Fortuny, Hermosillo, Heaton, & Pardee, 1999), we also examined how much of the
variance in each outcome measure is explained by these predictive variables.

METHOD
Subjects
Participants were selected from two larger normative studies of native Spanish speakers of
Mexican descent from the U.S.–Mexico border region (see Table 1). To be selected from
these normative samples, subjects were required to have valid scores for the Stroop test,
PMR in Spanish, and FAS in English, have at least 7 years of education, and be between 18
and 65 years old. This resulted in inclusion of 118 subjects from San Diego, California, and
Tucson, Arizona, that were participants in a norming effort for an expanded Halstead-Reitan
battery in Spanish, as well as 23 participants from the normative group for La Batería
Neuropsicológica en Español (Artiola i Fortuny et al., 1999). As part of the larger normative
studies, efforts were made to recruit participants into the approximate same sized cells
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according to sex as well as pre-set age and education ranges. The resulting sample for the
present study was made up of 70 men and 71 women ranging in age from 20 to 63 years (M
=36.8; SD =9.5), and with educational attainment between 8 and 20 years (M =12.5; SD
=3.1) (see Table 2).

Study participants responded to flyers or direct contact with recruiters in community

settings. They were selected on the basis of having reason to spend time in the United States
on a regular basis (e.g., for work, school, place of residence). All participants expressed a
desire to be tested in Spanish and a language use questionnaire was used to confirm that
Spanish was their preferred language. As suggested by Artiola i Fortuny et al. (1999), The
Controlled Oral Word Association Test (COWAT) (Benton & Hamsher, 1989) was
administered in both English and Spanish to provide an objective measure of the degree of

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verbal fluency in each language. Subsequently, a measure of relative English fluency was
calculated to confirm language dominance. On average, participants generated 40.3 (SD
=12.2) words in Spanish with letters P-M-R, compared to 23.6 (SD =12.8) words in English
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using the letters F-A-S. These letter sets are roughly matched for difficulty across languages
(Artiola i Fortuny et al., 1999). Subjects enrolled in the normative studies were carefully
screened to ensure that they had no significant history of medical, psychiatric,
developmental, or substance abuse disorders that could confound neuropsychological
performance.

The Dominance Index

As we were interested in the effects of second language ability on native language test
performance, we calculated a continuous language dominance index reflecting relative
English fluency, as follows: (FAS/FAS+ PMR). Thus, the index provides the ratio of
English words to total words produced in both languages. A ratio is preferred over a raw
English fluency score because it avoids using level of performance on one
neuropsychological test (phonemic fluency) to predict level of performance on another
neuropsychological test (Stroop, 1935), which would be expected to be correlated for
reasons not related to bilingual language control. With this measure, two participants with
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very different levels of overall ability could have comparable indices of language
dominance. To illustrate, a person who produced 25 words in English and 50 words in
Spanish (25/75 = 0.33) would have a comparable level of relative English-to-Spanish
fluency to that of a person who produced 5 words in English and 10 words in Spanish (5/15
= 0.33). While their overall levels of performance are quite different, relative English-to-
Spanish fluency is equivalent. Moreover, using overall fluency as the denominator makes
the range of English ability easy to interpret, with 0 corresponding to no English fluency
(i.e., complete Spanish dominance), 0.5 reflecting identical English and Spanish ability, and
1 corresponding to complete English dominance (i.e., no Spanish fluency).

The dominance index scores ranged from 0 to 0.66 (M =0.35; SD =0.12) with a higher score
corresponding to higher relative English fluency. Because there is no established cutpoint
for deciding what degree of difference between Spanish letter fluency (PMR) and English
letter fluency (FAS) scores ought to be considered a meaningful difference, and because we
wanted to capture a wider range of English fluency, we included 11 participants with scores
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above 0.50 but not exceeding the upper tertile of the distribution on the dominance index (>.
66), which would indicate strong English dominance. Although these few individuals
obtained higher English than Spanish COWAT scores, all preferred to be tested in Spanish
and reported being Spanish-dominant on the language use assessment questionnaires.

For analyses, the relationship between the dominance index, sex, age and years of education
was first explored using pairwise correlation analyses between the predictive variables and
each outcome variable. In the analyses of primary interest, the effects of relative English
fluency on a Spanish version of the Stroop test were examined with simultaneous regression
analysis including the dominance index, sex, education, and age as predictors.

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Procedure and Measure

This study was approved by the institutional human research protections program.
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Participants received the Spanish version of the Stroop Test (Artiola i Fortuny et al., 1999)
as part of a larger battery of neuropsychological tests. The Stroop test is widely used to
assess executive function (i.e., selective attention and cognitive flexibility). Instructions
were administered according to the test manual by Artiola i Fortuny et al. (1999). Testing
was performed by trained bilingual psychometrists using standardized procedures. Each trial
was scored as the number of correct responses achieved within 45 seconds, according to
published guidelines (Golden & Freshwater, 2002). For the Word Reading trial, the
examinee is asked to read the names of colors written in black ink on a piece of paper
containing five columns and 20 rows of words. For the Color Naming trial, the stimulus
sheet contains the same number of rows and columns with stimuli made up of 4 Xs printed
in red, green, or blue ink. In the Color–Word incongruent trial, the names of the colors
appear in different ink color than the typed color word (e.g., the word “red” printed in blue
ink). Participants are asked to inhibit reading the word and name the color of the ink instead.
For all trials, participants were instructed not to stop until instructed by the examiner. They
were told to go back to the first column should they complete all 5 columns. This occurred
only in the Word Reading condition where participants, on average, finished reading the five
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columns plus six words (M =106.7; SD =14.3). When an error was made, the participant was
corrected immediately and instructed to continue with the task. The number of correct
responses in 45 seconds was recorded by the examiner for each trial.

RESULTS
Pairwise bivariate correlations among predictors revealed that higher education was
associated with higher dominance index (r =.41; p <.001). Age was not correlated with
either years of education or the dominance index. Men and women did not differ
significantly in age, years of education or the dominance index. Univariate correlations
between each outcome variable and independent variables were followed by simultaneous
multiple regression analysis with the dominance index, years of education, age, and sex as
predictive variables.

Color–Word Incongruent Trial

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Men and women differed significantly on the Color–Word incongruent trial. Pairwise
correlation analysis showed that age was not associated with incongruent trial performance,
while better educated and more English-fluent speakers, performed better. Scores on the
Color–Word incongruent trial were significantly correlated with the dominance index (r
=0.27; p =.001) and years of education (r =0.18; p =.03). However, the dominance index
seemed to be a more powerful predictor than education, which did not explain any unique
variance in Stroop performance in a multivariate model. That is, simultaneous regression
analysis revealed that, after controlling for education and age, only the dominance index (β
=15.86; p =.008) and sex (β =1.78; p =.008), predicted incongruent trial scores [R2 =0.12;
F(4,136) =4.87; p =.001]. See Table 3. On average, women (M =44.3; SD =7.1) named three
more colors in the incongruent condition than did men (M =40.9; SD =8.8). This difference
was not driven by education or age differences in men and women, since their overall means

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were comparable for both demographic variables. However, as a possible explanation for the
unanticipated sex difference, we considered the possibility that the effects of bilingualism
could be different at the lower versus higher levels of education for men and women. For
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this purpose, we dichotomized participants into bilingual and monolingual based on the
dominance index. Based on our original rationale of dividing the dominance index into
tertiles to exclude persons who were strongly English dominant (>0.66), we decided to
classify participants into Spanish-dominant and bilingual based on these tertiles. As such,
participants in the lower tertile (index ≤0.33) were classified as Spanish-dominant and those
with indices in the middle tertile (between 0.34 and 0.66) were classified as bilingual.
However, when we dichotomized the groups into bilingual and monolingual, we found that
bilingual men and women tended to be more educated than the Spanish dominant men and
women, with no interaction by sex (p =.51). The difference in years of education between
bilinguals and Spanish dominants was the same for both sexes (see Table 4). Thus, gender
differences could not be explained by education effects. Similarly, age does not account for
these differences either. Still, the bilingual effect for this sample appears to be driven by the
bilingual effect in men, which is absent in the women. That is, both bilingual and
monolingual females, on average, were able to produce the same number of ink colors
(while inhibiting the prepotent reading response) than did the bilingual man. The
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monolingual men, on the other hand, named approximately six less number of ink colors
(while inhibiting the prepotent reading response).

Word Reading and Color Naming

On average, women (M =74.5; SD =10.1) were faster, producing approximately 4 more
color names than men (M =70.6; SD =10.7), but no significant differences were found in
their ability to read words.

In contrast with the Color–Word trial, the dominance index was not significantly correlated
with Word Reading (p =.46) or Color Naming scores (p =.26), nor were education or age
significantly correlated with these measures (all ps >.05). Simultaneous regression results
indicate that only gender was a significant predictor of the Color Naming score (β=1.96; p =.
03) with a marginally significant overall model, [R2 =0.07; F(4,136) =2.57; p =.04].

DISCUSSION AND CONCLUSIONS

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Previous studies examining the effects of bilingualism on the Stroop test have mostly been
conducted with young and well-educated college samples, where bilingualism has been
treated as a dichotomous variable, and often based on self-report measures of language
proficiency. Additionally, most studies of this sort have looked for effects of bilingualism in
the individual’s non-native language. Because there is great heterogeneity in the definition
of bilingualism, the current study aimed to understand how different degrees of English
proficiency, as are commonly observed in immigrant populations, would affect performance
on the Stroop task administered in Spanish. We tested these effects in a group of adults with
a broad range of age and education who identified Spanish as their first language. Results
revealed smaller Stroop effects for participants who had higher degree of relative English
fluency. Thus, participants with greater relative second-language ability were better at
suppressing the automatic reading response in their native language. Given that the

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dominance index and education were moderately correlated in our sample, education would
have also been expected to predict Stroop performance, as has been previously found
(Anstey, Matters, Brown, & Lord, 2000; Moering, Schinka, Mortimer, & Graves, 2004).
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However, the effect of second language fluency on the Stroop trial requiring inhibitory
control appeared to be independent of education once both variables were included in a
regression model. On the other hand, performance on the trials that require simple
processing speed was unrelated to second language fluency or education. These combined
results suggest that better second language fluency confers a true advantage in the ability to
suppress the unwanted prepotent response in the native language, and this effect is not
explained by differences in level of education.

An alternate explanation for these findings could be that as English fluency increases, word
reading abilities in Spanish decline, thereby reducing the Stroop effect and improving
incongruent trial scores. This could be particularly true in those people who had somewhat
better English fluency compared to Spanish (n =11). However, this explanation seems
unlikely since scores on the Spanish (PMR) and English (FAS) letter fluency tasks were
positively correlated. That is, there was no subtractive effect of bilingualism (instead,
increased English fluency was associated with increased Spanish fluency). Additionally,
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when dichotomized as monolingual and bilingual as described earlier, both groups had
comparable PMR (38.7 and 41.5, respectively) and Word Reading scores (104.6 and 108.2,
respectively; bilinguals, in fact, had slightly better reading scores). This suggests that the
advantage conferred by greater second language fluency is related to improved inhibitory
control rather than a handicap in the first language.

Previous studies examining the Stroop effect in bilingual individuals have shown mixed
results. When bilingual advantages are not found, studies have often been based on small
sample sizes, and as the methods have differed from those in our study, results are not
directly comparable (Gasquoine et al., 2007; Roselli et al., 2002). Other studies with larger
and more representative samples have also failed to find a bilingual effect on the Stroop test
(Razani, Burciaga, Madore, Wong, 2007). In this study, unlike the study conducted by
Bialystok et al. (2008), the ethnically diverse groups (Hispanics, Asian, Middle-Eastern)
may have varied significantly in level of English ability and that may have accounted for the
better performance of monolingual English speakers. Entry criteria for the ethnically diverse
group required that participants be fluently conversant in English and this included people
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who were born, raised, and fully educated in the United States but also people who received
all of their education in their native countries and who may not have been highly proficient
in English. The current study is novel in that it associates better second-language fluency
with better Stroop performance in the native language, along the full range of second
language knowledge, and including relatively unbalanced bilinguals.

The clinical implication of the findings reported here is that neuropsychological assessments
should include thorough information about a patient’s level of second language ability, since
the bilingual advantage found in this study and other recent studies suggests that the
interpretation standards for measures of executive function may need to take into account
second language fluency. That is, declines in executive functions may be underestimated in
speakers of a second language when using norms based on monolinguals. Therefore, in the

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future, we may want to consider adjusting normative standards for degree of second-
language knowledge as part of the demographic corrections (i.e., education, age, and sex).
This study suggests that clinicians testing native Spanish speakers in the United States
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should gather information about their English fluency. An index of the type used in the
current study can serve to guide a clinician regarding Stroop test performances that deviate
from normal in this population. For this purpose, Table 4 provides means and standard
deviations for participants who were classified as either bilingual or monolingual based on
the dominance index.

Additionally, in agreement with previous findings (Moering et al., 2004; Strickland, D’Elia,
James, & Stein, 1997) showing differences in men and women’s ability to name colors, this
study also suggests that performances between bilinguals and monolinguals should be
interpreted separately for men and women (see Table 4). The findings for sex differences in
the Color–Word incongruent trial in other studies have been mixed (Mitrushina, Boone,
Razani, & D’Elia, 2005). However, in the current study women had better ability to suppress
the unwanted response than did men, despite having equal levels English dominance and
education levels. Upon closer examination of the data, the relationship between the
dominance index and the incongruent trial score was found to be significant for men but not
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for women. Moreover, this bilingual effect appears driven by the men with lower relative
English fluency ratios when compared to other males with higher fluency ratios or women
overall. We also considered a possible differential effect of age for men and women, but the
distribution of scores for the incongruent trial across ages did not differ for the two groups.
As previously mentioned, while higher levels of education where associated with higher
relative English fluency (i.e., bilingualism), men and women had comparable levels of
education. Therefore, no demographic variables that could account for this apparent
interaction in this sample. Given that women significantly outscored men in the Color
Naming and Color–Word incongruent trial, it is possible that women may not benefit from
the bilingual experience as much as men do since their baseline performance is already
better. Rather than speculate further about the nature of this finding with our limited sample
size, we await replication of this effect in larger independent samples.

In summary, our most significant finding suggests that second language proficiency should
not be ignored even when testing people in their native language, since second language
proficiency seems to improve inhibitory control. As suggested by Bialystok and colleagues
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(2008), the Stroop incongruent trial would be analogous to the process in which a bilingual
person engages when trying to speak in a second language while suppressing their first
language. It remains to be understood whether individuals who became bilingual are better
at inhibiting non-target behavior to begin with, and therefore have an easier time acquiring a
second language, or if the ability to inhibit unwanted behavior becomes easier as the person
becomes more bilingual and increasingly practices inhibitory control. The effects reported
here are consistent with each of these possibilities.

Future research might also focus on the biological underpinnings of how second language
acquisition modifies brain function, and should explore whether socio-economic conditions
that differentiate monolinguals from bilinguals among immigrant groups are related to the
bilingual advantage rather than (or in addition to) any biological mechanisms associated

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with bilingualism, per se. These studies would be improved by using both objective and
subjective measures of bilingualism and measures of acculturation, which are often included
in studies where performance of bilinguals is examined. Such measures would have
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enhanced the current study since it is likely that participants with higher degrees of
bilingualism were also more acculturated and therefore possibly more “test savvy.” Last,
future research should examine the effects of bilingualism on neuropsychological
performance in other Hispanic groups, since English–Spanish bilinguals are a heterogeneous
group and results of the current study may not be generalizable to bilinguals in other parts of
the United States

Acknowledgments
The authors thank the members of the HIV Neurobehavioral Research Program and the participants of this study.
This manuscript and information contained in this manuscript have not been published previously. This work was
supported by NIH Grants MH62512, MH064907, and HD062163.

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Table 1

Demographics for entire sample

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(N =141)

M (SD) Range
Age 36.8 (9.5) 20–63
Education 12.5 (3.1) 8–20
% Men 49%
Spanish letter fluency: PMR 40.3 (12.2) 17–70
English letter fluency: FAS 23.6 (12.8) 1–62
Dominance Index .35 (.12) 0.0–0.66
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Table 2

Frequency distribution of age and sex by education groups

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Education groups

≤11 (n =43) 12 (n =41) 13–15 (n =26) ≥16 (n =31)

Age, mean (SD) 36.4 (9.1) 35.9 (10.0) 35.5 (10.0) 40.5 (8.0)
Education, mean (SD) 9.1 (0.9) 12 (0) 14.3 (0.7) 16.9 (1.5)
% Female 51 54 46 48
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Table 3

Beta weights for each predictor

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Age Gender Education Fluency Ratio

Word-Reading 0.14 −0.27 0.17 8.94
Color-Naming 0.005 1.96* 0.45 8.28

Color–Word Incongruent −0.02 1.78* 0.23 15.86*

*
p <.05.
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Table 4

Means and standard deviations for education and each Stroop condition by sex and bilingualism
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Males (n = 70) Females (n =71)

Bilinguals (n =41) Monolinguals (n =29) Bilinguals (n =42) Monolinguals (n =29)

Age 35.6 (10.4) 36.5 (7.9) 39.4 (9.4) 35.9 (9.2)
Education 13.9 (2.8) 11.0 (2.7) 13.5 (3.1) 11.2 (2.5)
Stroop Word-Reading 108.8 (14.3) 104.2 (14.5) 107.7 (14.5) 105.1 (14.1)
Stroop Color-Naming 73.1 (9.1) 67.3 (11.9)* 75.5 (10.2) 73.1 (10.0)

Stroop Color–Word 43.8 (7.3) 36.7 (9.1)** 44.4 (6.4) 44.2 (8.0)

Note. Participants in the lower tertile (index ≤ 0.33) were classified as Spanish-dominant and those with indices in the middle tertile (between 0.34
and 0.66) were classified as bilingual.
*
p <.05.
**
p <.005.
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NIH-PA Author Manuscript

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