An aberrant belief is extreme or unusual in nature. In the most serious cases these beliefs cause emotional distress in those who hold them, and typify the core symptoms of psychological disorders. Each of the chapters in this volume seeks to examine the role that biases in reasoning can play in the formation of aberrant beliefs.The chapters consider several conjectures about the role of reasoning in aberrant belief, including the role of the jumping to conclusion bias in delusional beliefs, the probabilistic bias in paranormal beliefs, the role of danger confirming reasoning in phobias, and the controversial notion that people with schizophrenia do not succumb to specific forms of reasoning bias. There are also chapters evaluating different theoretical perspectives, and suggestions for future research.Aberrant Beliefs and Reasoning is the first volume presenting an overview of contemporary research in this growing subject area. It will be essential reading for academics and students in the fields of human reasoning, cognitive psychology and philosophy, and will also be of great interest to clinicians and psychiatrists.