At the beginning of the project we carried out a comprehensive review about ERP studies investigating neural modulations during the performance of tasks used to investigate executive functions. After revising those studies, we have established specific differences between monolinguals and bilinguals that should be observed to claim the existence of a bilingual advantage in executive neural processing. This study, which was published in the prestigious journal Neuroscience & Biobehavioral Reviews, is a very relevant review article due to the lack of consensus to interpret ERP differences between monolinguals and bilinguals (especially in the absence of differences in the behavioural performance). Also, I carried out additional theoretical work by conducting a very exhaustive review on how EEG/ERP, transcranial magnetic stimulation and functional MRI studies using the Simon (which represents one of the most used paradigms to study executive functions) contributed to understand executive neural processing in the human brain.
A widely overlooked issue is the impossibility to conclude that bilingualism contributes to CR on the basis of the relationship between bilingualism and executive functions because executive functions and CR are not equivalent constructs. Moreover, the neural correlates of CR are still poorly understood. So, we analysed a set of previously collected data (specifically, about 90 older adults, which were divided into high and low CR groups) to investigate the interplay between executive functioning (by using behavioural and event-related brain potential correlates) and CR (by means of graph theoretical analysis of complex networks, which provide measures of brain connectivity that is thought to be the compensatory mechanism in high cognitive elderly). So far, we have obtained several ERP correlates distinguishing between high CR and low CR and, in general, ERP latencies are faster and ERP amplitudes are larger in high compared to low CR group.
There are other methodological problems contributing to the lack of consensus among the researchers studying relationships between bilingualism, executive functions and CR such as the biased interpretation of any difference as enhanced executive processing in bilinguals or the use of small samples. In this context, I have published an opinion paper explaining some procedures that would help to achieve a consensus among the researchers. In that study, I argue for publishing Registered Reports within this field of research to prevent biased results interpretations and improving the implementation of the scientific method. According to this view, we have pre-registered the main body of the research related to this project in the peer-reviewed journal Psychophysiology. We are now collecting data (we have argued that 160 participants divided in low CR monolinguals, low CR bilinguals, high CR monolinguals and high CR bilinguals will be needed) and we expect to submit the full manuscript within the next 18 months.
