A title in the modular "Principles of Psychology" series, designed for A- level and other introductory courses. While normal individuals obviously differ from each other in various ways, psychologists have emphasized differences in intelligence and personality. This emphasis is reflected in the book, and various different views are discussed at length.; Abnormality has always been a source of fascination, although it has been difficult to form a good understanding of why and how abnormality develops. Psychologists have also grappled with other complex issues, such as how to classify abnormal individuals and what forms of treatment will prove beneficial. In spite of complexities, much progress has been made.