High cognitive activation by complex tasks in English language teaching is the focus of this book. It is regarded to as one of the most crucial quality teaching criteria which particularly refers to internal reasoning process of learning helping students enhance competences and become autonomous. The motivation leading to this study was drawn after a teacher training workshop on "cognitive activation by complex tasks". Through passive observation, it has been revealed through this study that, trained teachers demonstrated a significant step in applying the knowledge got from the workshop. They found cognitive activation by complex tasks useful for better development of both basic interpersonal communicative skills (BICS) and cognitive academic language proficiency skills (CALPS), despite multidimensional challenges. It is obvious that cognitive activation strategy builds a class of strong thinkers ready to develop own thinking strategies to cope with complex situations around them. Besides, this book does not only highlight how EFL teachers implement cognitive activation by complex tasks, but also provides a didactic model of a teacher training.