The focus in this chapter is on methodological problems in cognitive-linguistic research, with particular attention to the bilingualism and the childhood language impairment literatures. The discussion is centered around the importance of having solid conceptual frameworks, appropriate participant selection criteria, sensitive and reliable tasks, and corresponding data analysis. Efficient and dynamic research designs are needed if we want to respond to the challenges created by today’s diverse language practices and life experiences of children. Although it is impossible to offer wide-ranging solutions to all of these questions in one chapter, the goal is to demonstrate the complexity of the problems and illustrate how the use of an individual-differences approach and the collaboration among researchers, educators, and clinicians may bridge the gap between scientific research and clinical and educational practice to improve research, assessment, and intervention of cognitive control in speakers from diverse cultural and linguistic backgrounds.

This chapter is a synthesis of the findings about the relationship between cognitive control and language. It provides a more holistic picture about this relationship with particular attention to the heterogeneity of the participants and the shortage of sufficiently sensitive, valid tasks. The discussion is centered around the need for more studies using an individual-differences approach and the ways this approach may be combined with experimental designs to provide a method within which variability in performance is viewed as key information. The findings suggest that we must broaden the language spectrum in our studies to include speakers of various languages at a variety of proficiency and ability levels. Additional focus is placed on the need for interprofessional collaborations among researchers across disciplines, as well as between researchers and practitioners and educators, in order to enhance our diagnostic and classification accuracy and to decrease the inconsistencies in findings across studies.

In this chapter, we reinforce the book’s aim to shed light on changes inflicted on language, cognition, and the brain rather than to focus on advantages and disadvantages of being bilingual. To obtain a more realistic picture of bilingualism, its assets (i.e., what is easier), and its difficulties (i.e., what is taxing and leads to high consumption of mental resources), we have drawn on research from various disciplines. We conclude the book by identifying complexity as the major issue for research on bilingualism. The complexity problem is fundamental to definitions of bilingualism and the characterization of bilingual participants in empirical studies, leading to discussions about its assessment as a dichotomous or continuous variable. Considering bilingualism as an experience and how such experience impacts overall language development, cognition, and the brain at different levels are related to usage-based approaches of examining bilingualism as well as a concern regarding confounding and moderating variables. The shift for designing research in the field of bilingualism seems to necessarily be more interdisciplinary in nature than in the past.