Simone E. Pfenninger is Professor of English Linguistics at the University of Zurich. Her principal research areas are variationist SLA, psycholinguistics, and multilingualism, especially in regard to quantitative approaches and statistical methods and techniques for language application in education.Julia Festman is Professor of Multilingualism at University College of Teacher Education Tyrol in Innsbruck. Her main research focus is on multilingualism on the individual, cognitive, and educational level. She combines psycholinguistic, neurolinguistic, and neuroscientific methods for investigating learning and processing of multiple languages.David Singleton is Emeritus Fellow at Trinity College Dublin. He served as Secretary General of AILA and as President of EUROSLA. He is a EUROSLA Distinguished Scholar and an Honorary Member of AILA.

• Chapter 1 Introduction: Seasons of life in SLAChapter 2 Infant and childhood bilingualism2.1 Impact of early exposure to two languages on brain development, functioning and structure2.1.1 The many shades of child bilingualism: Early and late bilinguals and beyond2.1.2 Age of onset of exposure to a second language linked to ultimate attainment only – but there is more2.1.3 Age of onset of exposure to a second language linked to influences on the brain2.2 Chronological age and maturation2.2.1 Chronological age, maturation and the brain2.2.2 Child language development and variability2.3 Learning environment as a complex socio-cultural variable: Setting the stage for early L2 learning2.4 From environment to input: Early experiences with language(s) and focus on input dependency (quantity and quality)2.5 Child-internal factors2.6 Idiosyncratic learner trajectories – from early on?2.7 Methodological envoiChapter 3 Dual language development in school-age children and adolescents3.1 Dual language development in schools3.1.1 Brain development as a basic challenge in adolescence3.1.2 Dual language learners (DLLs) in schools3.1.3 Some notes on the bilingual advantage3.2 The ‘earlier is better conundrum’ in school settings3.2.2 Intensity trumps quantity in foreign language instruction3.3 Methodological envoiChapter 4 Language learning in young adulthood and midlife4.1 Young adults4.1.1 Plurilingual couples 4.1.2 Opportunities for bi-/plurilingual love4.1.3 Planning and policy4.1.4 Love and language use: three cases4.1.5 Methodological envoi4.2 L2 acquisition in midlife4.2.1 Heritage languages4.2.2 Adult classroom learners in their home country or region4.2.3 Adult migrant foreign language acquirers4.2.4 Methodological envoiChapter 5 Complex and dynamic realities of second language (L2) learning later in life5.1 Additional language learning in the third age5.1.1 Inter-individual variation across the lifespan5.1.2 Intra-individual variation across the lifespan5.1.3 Intra-individual variation as a source of information5.1.4 Methodological envoi5.2 Cognitive decline or too much mileage? The causal story behind ageing and cognitive changes – and its implications for SLA5.3 Benefits of L2 learning in older adulthood5.3.1 Cognitive benefits of lifelong bilingualism5.3.2 Cognitive consequences of foreign language learning in old age5.3.3 Methodological envoi5.4 Implications for the third age FL classroom5.5 ICT usage among adult L2 learners5.6 Suggestions for future research on third-age additional language learning5.6.1 Reframing lifelong learning through personal narratives5.6.2 Narratives: understanding who we are, how to live, and what to do5.6.3 The narrative of decline as a dominant master narrative of ageing in Western societies5.6.4 The value of staying young5.6.5 Example of a dialogical narrative analysis with third age additional language learnersChapter 6 Re-examining threshold hypotheses: Continuity vs. cut-off points throughout the lifespan6.1 The (multiple) critical period(s) hypothesis as a biologically regulated threshold6.1.1 The notion of "critical period"6.1.2 Neurolinguists following in the footsteps of Penfield and Lenneberg6.1.3 Definitive onset, offset and terminus?6.1.4 Nativelikeness and the critical period6.1.5 Nativelikeness and the role of language aptitude6.1.6 Critical age or critical opportunity?6.1.7 Envoi6.2 Thresholds for cognitive and brain reserve capacities6.3 Retirement as a potentially significant life event altering the process of cognitive ageing and language acquisition, use and attrition6.3.1 Effects of occupation on cognitive functioning6.3.2 Experiences and perceptions of continuity in the transition from work to retirement6.3.3 Language acquisition, use and attrition across retirement age6.3.4 Methodological envoiChapter 7 Conclusions and future directions of research on lifelong L2 learning

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