This book presents an English translation, by Nicolas and Lamiell, of the entirety of a German-language text authored by William Stern (1871-1938) and published in 1900. Its publication is widely considered to mark the founding of that sub-discipline of psychology devoted to the systematic study of individual and group differences. The book includes an introductory chapter by Nicolas and Lamiell, placing Stern's work into historical context and discussing its influence on the work of scholars who followed.
By making this available for the first time for an Anglophone audience, it fills a significant gap in the history of psychology literature and offers a springboard into much needed critical discourse on the contemporary state of psychological testing in particular, and on the study of individual and group differences more broadly. It holds fresh insights for those specializing in the fields of personality psychology, educational psychology, and industrial-organizational psychology; as well as to practitioners in the fields of personal and educational counseling.

Foreword.- Introduction.- Part One: Nature, Tasks, and Methods of Differential Psychology.- Chapter 1: Nature and Tasks.- Chapter 2: Methods of Differential Psychology.- Part Two: On Certain Fields of Mental Differentiation and Their Experimental Treatment.- Chapter 3: Sensory sensitivity.- Chapter 4: Perceptual types.- Chapter 5: Memory Differentiation in memory contents.- Chapter 6: Associations.- Chapter 7: Apprehension types.- Chapter 8: Attention.- Chapter 9: Combinatorial ability.- Chapter 10: Judgment.- Chapter 11: Reaction types.- Chapter 12: Emotions.- Chapter 13: Mental tempo.- Chapter 14: Mental energetics.- Part Three: Bibliography.- Chapter 15: General Information.- Chapter 16: Character.- Chapter 16: Temperaments.- Chapter 17: Mental Tests.- Chapter 18: Sensory Sensitivity.- Chapter 19: Perceptual Types.- Chapter 20: Audition.- Chapter 21: Memory-based Representations.- Chapter 22: Comprehension, Judgment.- Chapter 23: Psychophysiology and Reaction Types.- Chapter 24:Energy (Will).- Chapter 25: List of Authors for the Bibliography (name index).