Diversity and Complexity: Some Perspectives on Instructed Second Language Acquisition

This special issue investigates the multifaceted relationship between linguistic diversity, structural complexity, and instructed second language acquisition (ISLA). Although bilingualism has become the global norm, research and educational practice still insufficiently reflect the full range of linguistic varieties and learner backgrounds. The issue highlights four central challenges: the persistent Anglocentrism in ISLA research, the unresolved debate on linguistic complexity, the need to disentangle structural complexity from learning difficulty, and the diverse forms that shape multilingual classrooms, ranging from learner profiles to linguistic repertoires and sociolinguistic contexts. The contributing studies examine a wide range of languages (German, minority Germanic varieties in Italy, Italian, Maltese, Portuguese, Russian) and focus on complex morphosyntactic structures, diverse learning environments, and pedagogical interventions tailored to multilingual and migratory settings. Together, they illustrate how pluralistic, inclusive, and theoretically informed approaches can enhance L2 learning, support linguistic minorities, and promote equitable educational practices in increasingly diverse societies.