This undergraduate textbook reviews psychological research in the major areas of reasoning and thinking: deduction, induction, hypothesis testing, probability judgement, and decision making. It also covers the major theoretical debates in each area, and devotes a chapter to one of the liveliest issues in the field: the question of human rationality. Central themes that recur throughout the book include not only rationality, but also the relation between normative theories such as logic, probability theory, and decision theory, and human performance, both in experiments and in the world outside the laboratory. No prior acquaintance with formal systems is assumed, and everyday examples are used throughout to illustrate technical and theoretical points. The book differs from others in the market firstly in the range of material covered: other tend to focus primarily on on either reasoning or thinking. It is also the first student-level text to survey an imporatant new theoretical perspective, the information-gain or rational analysis approach, and to review the rationality debate from the standpoint of psuchological research in a wide range of areas.