Most of the world population can communicate in another language and can be characterized as bilingual (BAKER, 2006[1]). A bilingual has two languages ​​operating in his/her cognitive system, as a continuous line from the monolingual towards the bilingual mode (GROSJEAN, 1985[2])1. It is about this topic that the Canadian professor and researcher Dr. Ellen Bialystok gives the conference Does Bilingualism Affect Cognitive and Brain Structures? Facts and Fictions[3] on June 30th, in the series of online lectures promoted by the Brazilian Linguistics Association (ABRALIN) during the coronavirus pandemic (COVID -19). The lecture was mediated by Dr. Ingrid Finger (UFRGS). Professor Bialystok presents the controversy behind the facts and myths about brain changes derived from bilingualism. For 2 hours, the researcher points out empirical data indicating that mastering more than one language modifies the brain's cognitive structure.

For Professor Bialystok, bilingualism is a source of cerebral neuroplasticity that allows reconfiguration of the attentional systems in the brain, leading to the differences in executive functions found in research over the past few decades. In this critical review, our goal is to discuss the evidence presented by Bialystok. The use of language is intense and recruits broad brain networks and cognitive systems. This use of more than one language is a source of brain plasticity through the joint activation of languages ​​and the conflict between them that leads to constant selection between languages. The researcher argues throughout her lecture that the consequence of the processes involved in the continuous demands for selection between languages ​​is the reorganization of the attentional brain networks in bilingual subjects.

Cognition is a dynamic system, changing according to stimuli, making new connections with each other (brain plasticity phenomenon) (STERN, 2002[4]). For this reason, factors such as: educational level, social environment, socioeconomic status, profession and bilingualism can significantly affect the brain (BIALYSTOK et al., 2007[5]). These elements help to form a cognitive reserve, a positive balance in the face of cognitive declines in aging. According to Bialystok, one of the main mechanisms that plays a role in compensating for cognitive losses is the frontal-parietal control system. The cognitive reserve (hypothesis) proposes that it can be derived from reconfigurations of the attentional systems and brain networks responsible for it, like the prefrontal cortex.

Attentional and executive processes underlie the bilingual experience. There is a need for attention, concentration, selectivity of stimuli, capacity for abstraction, planning, flexibility, mental control, self-control, working memory (HANDAM; BUENO, 2005[6]), in addition to the linguistic capacity necessary to speak (or to read and to understand) in one of the languages ​​that the individual knows. During reading, for example, you need a dynamic filtering of relevant information and, in parallel, an inhibition of irrelevant information for the reading in the proper language and not in the other one. In the case of adaptive control (GREEN; ABUTALEBI, 2013[7]), linguistic control processes adapt to the demands of an interactive context, therefore, there is a recruitment of the entire attentional systems. It is precisely the continuous exercise of these attentional systems that helps in the formation of the cognitive reserve, that is, in the reconfiguration of the attentional system of the bilingual individual that Professor Bialystok talks about. The bilingual must constantly select the language relevant to the communicative context and inhibit the non-relevant language.

According to Bialystok, the scientific evidence is quite clear in children and the elderly, but there is an inconsistency in replicating results of studies with adult participants. According to the researcher, We are looking at the wrong side, as there are contradictions regarding the concept of bilingual, age of the group of participants, contexts investigated, limitations of tasks such as Simon / Stroop task and Flanker test and there are also problems in the theoretical scope about executive functions (the researcher questions the Unified and Diversified model of Miyake et al. (2000[8])). Therefore, when asked about the importance of replicability of research results, a relevant issue in the experimental research area, the scientist alludes to an impossible repetition of a cake recipe, since each bilingual is endowed with unique characteristics - a cake, in fact, with its own peculiarities.

In this sense, the dichotomy about the bilingualism advantages versus disadvantages in the different stages of life converges to the acceptance that there is still much to be explored and that this precept may explain the lack of results corroboration, especially regarding adulthood. When we look carefully at the elements mentioned by Professor Bialystok, these variables are more difficult to be controlled in experimental studies with adult participants. Bilingual children in the studies are usually bilingual at an early age, which makes them similar participants to the research study. In the elderly, there are well known standardized tests of cognitive decline due to neurodegenerative diseases like Alzheimer's, which helps in conducting experimental research. In research with adults, it becomes more difficult to standardize among participants the amount of use of each language, the age when the participant learned the language, their educational level and also their socioeconomic level, the context investigated, the executive functions skills of each of the participants, among other elements cited by Bialystok.

Bilingual children usually outperform monolinguals in executive functions (MARTIN-RHEE; BIALYSTOK, 2008[9]), may have greater mental flexibility (PEAL; LAMBERT, 1962[10]), metalinguistic awareness (CUMMINS, 1978[11]) and greater creativity (KESSLER; QUINN, 1987[12]), but they may have a smaller vocabulary (BIALYSTOK; FENG, 2011[13]), less speed in lexical access (GOLLAN et al., 2005[14]) and less verbal fluency (BIALYSTOK; FENG, 2011[13]). This is probably because both languages ​​of the bilingual person share brain networks, so access to lexical items may be slower due to the competition between the two languages, two terms - one in each language - with similar semantic meanings. And the number of lexical items in each language may be less compared to the vocabulary of a monolingual, but greater if we consider the lexical items of the two languages. The Canadian researcher points out that in congruent and incongruent stimuli decision tasks (Simon´s task, for example), bilingual children systematically obtain shorter response times, as seen in the research by Martin-Rhee and Bialystok (2008[9]) and Emmorey, Luk, Pyers and Bialystok (2008[15]). This result is consistent with the attentional system reconfiguration of the bilinguals that brings them advantages and faster responses, even in the congruent items of these selective attention tasks.

In adults, there are positive differences for bilinguals in executive functions related to inhibitory control (BIALYSTOK et al., 2004[16]) and greater promotion of cognitive reserve (BIALYSTOK et al., 2007[5]), but they are faced with problems in lexical access (GOLLAN et al., 2005[17]), in the lexical decision (RANSDELL; FISCHLER, 1987[18]), in the semantic fluency (GOLLAN et al., 2002[14]) and with the on the tip of the tongue effect2 (GOLLAN; ACENAS, 2004[19]). Bialystok reports that most studies with adult individuals investigate young university students, impairing the generalization of the results. When presenting data from Paap and Greenberg (2013[20]) on response times of young bilinguals in Simon's Task, the Professor argues that the Paap and Greenberg (2013[20]) replication of Bialystok et al. (2005[21]) results is probably due to the context that is the same in both studies. The differences in response time between monolinguals and bilinguals disappear when it comes to a young population with a high educational level, also exemplified in Grundy et al. (2017[22]) data. It happens, according to the Bialystok, due to the lack of sensitivity of the tasks that leads to a ceiling effect. And it is one of the answers to the controversial data found in the cognitive advantages (or not) of bilingual adults.

Bialystok highlights the most positive balance of reconfiguring attentional processes at the last phase of life. It is known that, as you get older, there may be a decrease in cognitive skills, such as attention, control and memory. However, factors such as the bilinguals exercise of attention can compute more quality of life for them. More precisely, bilingualism provides a delay of approximately 4 years in the onset of Alzheimer's symptoms in an elderly population predisposed to the disease (BIALYSTOK et al., 2007[5]). The bilingual advantage comes into play as we age, when we most need the compensatory resources of attention.

The search for differences between bilingual and monolingual still persists. Ellen Bialystok showed us the evolution of scientific data and gave us some directions to next research. Perhaps, over the years, we have not observed yet bilingual under all possible perspectives. We may need to reflect more on the topic, considering the context, for example. In Brazil, the country's continental dimensions, the proximity and knowledge about different languages besides Brazilian Portuguese depending on the country’s region, the social, cultural and socioeconomic characteristics of the population, the educational and literacy level of the bilinguals imposes different elements to our attempt for a Brazilian cake recipe, so it is still under construction. Much research has been done lately, however, there is still a long way journey towards answers about the view of bilingualism of new era.