In this paper we describe a taxonomy of task demands which distinguishes between Task Complexity, Task Condition and Task Difficulty. We then describe three theoretical claims and predictions of the Cognition Hypothesis (Robinson 2001(Robinson , 2003b(Robinson , 2005a The Cognition Hypothesis: Task complexity, task design and task sequencingThis special issue consists of a theoretical overview of two models of attention that have prompted extensive research into the effects of task demands on selective attention and co-ordination of attentional resources during dual and multitask performance, followed by four empirical studies examining the effects of manipulating dimensions of task complexity on; (i) the accuracy, fluency and complexity of second language (L2) speech production; (ii) the extent of interaction and uptake of premodified input occurring during task performance, and iii) learner perceptions of task difficulty. A great number of previous studies have examined the effects of one or another aspect of L2 task demands, such as the availability of planning time (see Ellis 2005), or the nature and extent of participation on tasks (see Pica, Kanagy and Falodun 1993), individually. Drawing on this, and other previous research the studies in this special issue all address the issue of task complexity in the Triadic Componential Framework (Robinson 2001(Robinson , 2005a(Robinson , 2007a which specifies component dimensions of task complexity in terms of three superordinate cognitive, interactive and learner factors in order that each dimension can be studied separately, and also that

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This study explored the usefulness of dual-task methodology, selfratings, and expert judgments in assessing task-generated cognitive demands as a way to provide validity evidence for manipulations of task complexity. The participants were 96 students and 61 English as a second language (ESL) teachers. The students, 48 English native speakers and 48 ESL speakers, carried out simple and complex versions of three oral tasks-a picture narrative, a map task, and a decision-making task.Half of the students completed the tasks under a dual-task condition. The remaining half performed the tasks under a single-task condition without a secondary task. Participants in the single condition were asked to rate their perceived mental effort and task diffi culty. The ESL teachers provided expert judgments of anticipated mental effort and task diffi culty along with explanations for their ratings via an online questionnaire. As predicted, the more complex task versions were found and judged to pose greater cognitive effort on most measures.

The goal of this study is to investigate the impact of manipulating the cognitive complexity of three different types of oral tasks on interaction. The study first considers the concepts of task complexity and interaction and then examines the specific studies that have looked at the effects of increasing task complexity on conversational interaction. In the experiment, learners of English as a foreign language organized into 27 dyads carry out three different types of tasks: a narrative reconstruction task, an instruction-giving map task, and a decision-making task. Two different versions of each task (Robinson 2001a(Robinson , 2003(Robinson , 2005(Robinson , 2007bSkehan and Foster 2001), and how different task types may variously affect the way interaction proceeds during task performance.

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The goal of this study is to investigate the role of working memory capacity in L2 attainment and performance. The study uses an L1 reading span task to measure working memory of a group of 59 highintermediate/advanced learners of English, and a film retelling task to measure their oral production. The analysis first showed a moderate to high correlation between proficiency measured by a general proficiency test and learners' fluency, lexical complexity, and accuracy but not structural complexity on the retelling task. Secondly, no correlation was found between overall proficiency and working memory. Thirdly, a weak correlation was found between fluency and lexical complexity, and working memory. When the group was split into top and bottom levels of proficiency, moderate correlations were found between lexical complexity and working memory only for the high-proficiency group. The results are discussed in the light of previous research. KEY WORDS:Working memory, language learning aptitude, fluency, lexical complexity, structural complexity, accuracy, narrative performance. RESUMENEl objetivo de este estudio es investigar el rol de la capacidad de memoria operativa en la proficiencia y la producción en una L2. El estudio utiliza una tarea de reading span en la L1 para medir la memoria operativa de un grupo de 59 estudiantes de inglés de nivel intermedio alto/avanzado, y una tarea narrativa para medir su producción oral. Los análisis muestran correlaciones significativas entre la proficiencia medida por un test de proficiencia general y la fluidez, complejidad léxica, y corrección, aunque no con la complejidad estructural. Las correlaciones también son positivas y significativas entre la memoria operativa y la fluidez y complejidad léxica, pero no se observa una correlación significativa entre la proficiencia general y la memoria operativa. Cuando se divide el grupo entre los niveles más altos y más bajos se encuentran correlaciones moderadas entre la complejidad léxica y la memoria operativa sólo para el grupo de proficiencia alta. Los resultados se analizan en base a los escasos trabajos previos.

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In this article we explore how oral and written modes may differentially influence processes involved in second language acquisition (SLA) in the context of task-based language teaching (TBLT). We first start by reflecting on the differences between spoken and written language. In what follows, we provide a general description of tasks in relation to the SLA processes. We then establish the links between the learning processes and task phases/features in the two modes. Concluding that the role of mode has been underresearched, we call for a more integrative and mode-sensitive TBLT research agenda, in which hybridness of discourse (i.e., mingling of the two modes within one communicative event/task) is taken into account.