Recently, interest in executive functions (EFs) has grown, with research showing that these abilities predict success in school and, more generally, life [
1,
2,
3]. Attention control is an EF skill that is critical for operating efficiently in daily life, and gaps in this and other EFs have been shown to have severe consequences over the life course [
4]. Additionally, longitudinal studies have found that attention deficit hyperactivity disorder (ADHD) is related to long-term impairment in EF, from childhood into adulthood [
5,
6,
7]. Since some evidence suggests that bilingual individuals outperform monolingual individuals in response time (RT) (reflecting attention control) [
8], and bilingualism is generally associated with a cognitive advantage, it seems relevant to investigate the cultural spaces that might provide the best learning experiences for children, to inform the development of cognitive enhancement programs.
Recent research on bilingualism has produced mixed findings on the bilingual advantage. In more detail, a growing body of research is providing evidence that different bilingual profiles impact attentional skills differently. Since bilingual individuals must constantly control for the interference of another language, they may be disadvantaged on verbal tasks. On the other hand, bilingual individuals (particularly those living in a mixed-language environment) may benefit from the constant switching between languages, which offers them daily training to enhance their switching ability. Additionally, performance differences may arise from differences in ethnicity and socioeconomic status (SES). To address this, Morton and Harper [
9] compared bilingual and monolingual children of identical ethnic backgrounds and SES. While the bilingual and monolingual children performed identically, children from higher SES families were advantaged compared to children from lower SES families. When the authors controlled for disparities in SES and ethnicity, the bilingual advantage in cognitive control was attenuated.
Further research is needed to investigate the factors (e.g., SES) that may distinguish different types of bilingualism, to determine which provide an advantage and which do not.
1.1. Bilingualism and the Attentional Network
Studies demonstrating the benefits of bilingualism in the growth of cognitive processes have highlighted that the ability to speak two languages implies a suppression of the language that is not being spoken at any given time. The continuous activity of selecting and inhibiting language, according to the context, should imply better training of attentional networks, representing an advantage of bilingualism [
10]. According to Bialystok [
11], bilingual individuals also have an EF advantage because they are constantly training to conduct a conversation in context, and require continuous access to working memory. Laurent and Martinot [
12] found that school-aged children learning in a bilingual environment began to show the advantage of phonological awareness (one of the components of working memory) at the age of 9 years. Indeed, working memory is very important to conversation—particularly the ability of conversation partners to establish a joint perspective. Furthermore, in conversation, it is necessary to choose the appropriate language (and inhibit the other language) and observe what happens during the interaction (demonstrating cognitive flexibility).
Research has demonstrated that there is a close relationship between language skills and EFs [
13], with Moreno et al. showing that music therapy training can improve both [
14]. The language-based cognitive advantage is mainly reflected in tasks involving attentional networks [
15,
16]. According to Green
’s joint activation model (1998) [
17], a bilingual individual
’s brain is always engaged in both languages, regardless of the language being spoken at any given time. Therefore, it is necessary for a general suppression mechanism to inhibit activation of the non-target language. Monolingual individuals, in contrast, do not seem to require this suppression strategy. However, recent evidence shows that the bilingual advantage is more evident in executive attention than in inhibition.
Multilingualism tends to promote attentional disengagement, rather than overall inhibition, which is why it is visible in the sequential but does not demonstrate a traditional congruency effect [
18]. Attentional disengagement is an aspect of executive attention that terminates attention to previous stimuli and reduces their influence on current processing. Some studies have found that differences between monolingual and bilingual children reduce when the groups are matched for general ability [
19] and SES [
20]. Other studies have suggested that monolingual-bilingual differences in cognitive abilities [
19] are dependent on SES [
20] and relate to processing efficiency. More recently, Naeem et al. [
21] found that bilingualism had little effect on individuals with high SES but was essential for promoting processing speed among low-SES adults aged 18–30 years. Therefore, conflict adaptation paradigms may facilitate easier detection of the bilingual advantage than simple interference paradigms [
18].
Bilingual individuals have significant experience disengaging attention from prior stimuli, due to the need to manage two languages. As a result, they are typically more immune to the impact of previous stimuli on current processing than monolingual individuals. In line with this, previous research has connected differences in conflict adaptation to differences in executive attention processes [
22]. However, as Paap et al. described [
23], “bilingual advantages in executive functioning either do not exist or are restricted to particular and undetermined circumstances.” The authors noted that 80% of tests after 2011 failed to obtain results supporting the bilingual effect. They theorized that previous research on this topic might have been limited by an inability to control for various external factors (e.g., the experimental task, participants’ SES and cultural and linguistic backgrounds) and small sample sizes.
Of note, low SES has been associated with lower cognitive performance [
24]. Given the prevalence of the association between low SES and reduced vocabulary in bilingual individuals, several authors have emphasized the importance of analyzing this factor and monitoring its effects when a statistically significant difference is found between groups. Although many authors (e.g., [
25,
26]) have expressed that statistically controlling for this variable is the most appropriate approach, others have claimed that SES is a specific feature of the population of interest [
27], and that discrepancies in SES between monolingual and bilingual populations reflect variations in attentional disengagement [
19,
28,
29]. A recent study by Orsolini et al. [
30] investigated the role of working memory in reading comprehension between monolingual and bilingual Italian children. The results showed that working memory supported reading comprehension only indirectly. Indeed, written text comprehension is often described as a complex dual process involving working memory: multiple sources of information must be coordinated to constrain the development of a text representation, while relevant semantic content is kept alive in short-term memory. This dual process requires the direct involvement of the central executive. However, it does not appear to apply to elementary school students. A study found that monolingual children’s comprehension of an oral text was strongly related to their working memory skills; however, bilingual children showed no indirect effect of working memory on their reading comprehension [
30].
Bilingual individuals are required to continuously handle two languages while speaking. This may have a general impact on their attentional networks. Some studies have reported that bilingualism is associated with better executive control. The most suitable model for analyzing the executive component of attention separately from other components (i.e., alerting, orienting) seems to be that of attentional networks. Costa et al. [
14], testing young monolingual and bilingual adults with the Attentional Network Task (ANT), showed that bilingual individuals were quicker at completing the task and more effective in their executive control and alerting networks. In particular, they benefited more from the presentation of alerting cues and were more efficient at resolving conflicting information. Additionally, compared to monolingual individuals, bilingual individuals had lower switching costs between trials. These findings suggest that bilingualism may impact young adults’ ability to develop effective attentional processes, precisely when that ability is expected to be at its peak.
Recent research by Park et al. [
31] demonstrated that executive control was not affected by bilingual experience and was worse in children with developmental language disorders than in children with typical development. At least for children in this age range, dual language experience has been shown to have little impact on these skills. Tran, Arreondo, and Yoshida [
32] observed that culture significantly impacted the development of alerting and executive control attentional networks in a sample of 3-year-old monolingual and bilingual children from the United States, Argentina, and Vietnam. Children were longitudinally tested over five periods, using the ANT. The authors divided the sample according to the culture of membership (based on the flexibility of social structure), and the results showed that, when other factors (e.g., SES, vocabulary, age) were controlled for, culture significantly impacted the development of alerting and executive control attentional networks. In contrast, language status was only significant for the executive control attentional network.
1.2. Attentional Network and Socioeconomic Status
SES, which is often measured as a combination of education, income, and occupation, has been found to significantly impact attentional function and, more specifically, attentional regulation. For instance, children from low-SES families have been shown to frequently exhibit poor self-regulation [
33]—an index of executive control maturity. Studies have also shown that children in middle-SES families tend to outperform their peers on executive control [
33,
34]. Furthermore, it appears that family SES modifies the mechanism of attention disengagement, which is essential for the development of attention regulation [
35]. Several findings have linked low SES to poorer attention regulation to emotional stimuli [
35]. In particular, children in low-SES families tend to show a diminished activation of brain structures involved in the voluntary control of attention as adults, when asked to regulate their emotions in response to negative valence stimuli. In addition, infants raised in deprived home environments have been found to show increased negative affectivity, suggesting a link between these variables.
Infants with different temperamental profiles may also be more or less influenced by the environment. One study examined whether stress levels in parents and adolescents were associated with SES and executive functioning in adolescents living in urban areas, finding that parental stress was directly related to adolescent stress, and adolescent stress was directly related to the behavioral components of EF (i.e., emotion control, set-shifting, inhibition) [
36]. Finally, Mezzacappa [
37] found that children with higher SES were faster and more efficient on the alerting and conflict trials of the children’s ANT than children with lower SES—a finding with direct implications for the present study. In addition, low SES—and particularly a poor quality home environment—has been shown to indirectly affect children’s inhibitory control and sustained attention [
37].
The lack of a systematic measure of SES in previous studies may have led to an overestimation of the bilingual advantage. For example, Ladas, Carrol, and Vivas [
38] found that the bilingual advantage considerably reduced when monolingual and bilingual participants were matched for SES. Low SES has also been shown to be associated with high levels of stress [
39], which can alter cognitive functions, including selective attention. The literature also suggests a possible link between children’s learning environment and the neural correlates of attention. Families with low SES most likely live in chaotic, noisy, and crowded environments [
41], and such poor environments have been associated with factors leading to chronic stress, which can affect well-being [
40]. Additionally, chaotic environments are unpredictable and inconsistent, and often lacking in routine, which may interfere with healthy development [
42].
How do bilingual factors such as the age of learning two languages, language use, and language proficiency affect brain connectivity? The literature suggests that early, lifelong bilingualism alters the structure of gray and white matter in the brain. For example, in studies of adults, greater gray matter (in terms of volume and density) has been found in regions associated with language, such as the bilateral inferior frontal gyrus (IFG), inferior parietal lobule, anterior cingulate cortex, caudate, and putamen [
17,
42]. In a more recent study involving a different group of highly competent bilingual adults, the same relationship was found in the bilateral IFG. In addition, the authors found that better functional connectivity between cortical and subcortical brain regions, particularly between the left caudate and bilateral superior temporal gyrus, and the anterior cingulate cortex and left putamen, correlated positively with a greater “diversity of language use” (i.e., in an environment where both languages were frequently used and separate use of the languages was not routine) [
43]. Overall, there is growing evidence that factors related to bilingualism influence functional connectivity in the brain. However, little is known about how these connectivity changes might relate to executive control performance. In addition, there is growing evidence that bilingualism affects the organization of gray and white matter in the brain. However, a recent study of preschool children (i.e., aged 3–5 years) found no structural changes in the IFG, but more robust functional connectivity in bilingual children than monolingual children, suggesting that structural changes may manifest only after continuous exposure to two languages [
44].
1.3. Study Aim
The present study aimed at analyzing how SES and bilingualism interact with the attentional network in school-aged children, by comparing the performance of bilingual and monolingual third-, fourth-, and fifth-grade children on attentional and cognitive tasks. Specifically, participants were assessed using an attentional task (i.e., the ANT) that evaluated their attentional alert, orienting, and executive conflict networks, as well as several tests of working memory, short-term memory, and linguistic receptivity. Data were also collected on the family SES and children’s IQ. We chose to analyze the performance of children aged 7–11 years, to minimize the risk that the effects of language acquisition would be reflected in the efficiency of the attentional networks.
The above-cited literature suggests that parental SES has a critical impact on children’s cognitive development. However, it is not clear whether this effect might vary as a function of children’s multilingual status. The present study suggests that culture and bilingualism may interact to better explain the previously observed cognitive benefits of bilingualism and the growing discrepancy in the literature over these benefits.