This first book devoted exclusively to the cognition hypothesis (CH) considers the hypothesis through 12 chapters that address second language (L2) task complexity. In brief, the CH predicts that manipulating pedagogic task demands can influence L2 production, interaction, uptake of modified input, and the extent to which individual differences moderate learning and performance.

Part 1 outlines the theoretical and methodological foundations of the CH. In the opening chapter, Robinson provides an overview of the CH in terms of its rationale, operationalization, and predictions. Following this overview, Kormos situates key psycholinguistic constructs invoked in the CH (e.g., attention) within a bilingual model of speech production. In chapter 3, Wulff and Gries present a corpus-based approach to defining and measuring accuracy, illustrated by two case studies. By expanding previous accounts (e.g., Robinson & Gilabert, Reference Robinson and Gilabert2007), this preliminary section offers background while also engaging readers acquainted with the hypothesis. Remaining chapters describe studies on various dimensions of the CH.

The focus of Part 2 is task complexity and mode, which refers to written versus spoken modes of production or, in the case of the spoken mode, monologic versus dialogic modes. Kuiken and Vedder (chapter 4) compare the syntactic complexity, accuracy, and lexis of Italian learners performing a written or spoken task. Raising task demands reduced errors in both modes and had no significant effect on lexis in either mode. In chapter 5, Gilabert, Barón, and Levkina explore relationships between task complexity, mode, and proficiency by reexamining two studies on English as a foreign language (EFL) learners in Spain. They note that proficiency correlated more strongly with measures of complexity, accuracy, and fluency in monologic than in dialogic conditions.

Part 3 deals with task-based interaction and the CH. Michel’s chapter investigates the effects of task complexity (i.e., simple vs. complex) and mode (i.e., monologic vs. dialogic) with L2 Dutch learners. Tasks made more complex by adding elements led to increased lexical diversity across monologic and dialogic conditions. Additionally, the interactive nature of the dialogic tasks yielded greater accuracy and fluency—but less complex syntax—when compared to monologues. Nuevo, Adams, and Ross-Feldman (chapter 7) assess the impact of increased task complexity on modified output and subsequent learning. For the most part, complex conditions did not increase modified output for English as a second language learners. Yet, interestingly, different kinds of modifications were associated with gains under high versus low reasoning conditions. In the following chapter, Révész, Sachs, and Mackey probe the relation between task complexity (+/− visual context) and uptake in a Hungarian EFL context and report that complexity did not predict uptake in response to recasts. Modeling the relationship between task demands, uptake, and development, they uncover a positive relationship between rate of uptake and gain scores, but only in the less complex (+ visual context) group.

The last section, Part 4, examines individual differences and task complexity. Chapters 9 and 10 employ narrative tasks also studied in a Hungarian EFL context. Albert reports in detail on creativity and L2 production, finding moderate relationships between performance and some measures of creativity—mainly in the complex task—as the CH predicts. Kormos and Trebits try to link oral production and working memory. Performance was similar across learners whose digit spans ranged from 4–7. Next, Kim and Tracy-Ventura (chapter 11) investigate the role of speaking anxiety in tasks that vary in reasoning demands in a Korean EFL setting. The most complex group consistently scored above two others on posttests, as the CH predicts; however, this was true regardless of anxiety. Chapter 12 (Ishikawa) reports on Japanese EFL learners’ perceptions during role-play tasks at three levels of reasoning and demonstrate the effects of increasing task demands on self-ratings of concentration, difficulty, and interest.

As Robinson notes, “it is still too soon to expect definitive answers” (p. 28) regarding L2 task complexity, learning, and performance. Nonetheless, this collection documents a broad spectrum of recent work motivated by the CH that seeks to inform theory and practice in task-based language teaching. Each section offers unique perspectives on task complexity, establishing its relevance to L2 instruction. These insights from a range of experts add to the volume’s overall quality. This book should therefore find a wide audience among graduate students, language teachers, and researchers.