The Great Psychology Delusion takes an unflinching look at some of the foundational assumptions of psychological science. Exploring long-standing unanswered critiques of psychological research in a way that is detailed but accessible, the book brings together a wealth of material that challenges our understanding of what the science of psychology really is, and how the subject matter of that science should be conceived. Identifying a Great Delusion (that there is a coherent discipline of psychology with sound foundations), the authors explore a number of more specific delusions regarding scientific practice in psychology. These include the problematic assumptions of core statistical analyses, questionable aspects of frequently used experimental designs and continued frictions regarding the much-aspired-to scientist-practitioner model. The delusions produce the uncomfortable state in which we find much of modern psychological science - theoretically challenged, poorly replicated and with questionable real-world value. This unsentimental examination of the state of things nevertheless allows the authors to identify concrete steps that the scientific community can take to re-ground psychological research and move forward to a successful science studying the richest and most complex phenomena we know of: us. This book will interest all people interested in psychological science, from undergraduate students to researchers.