Gerard Heymans (1857-1930) was the founder of psychology in the Netherlands, and established the first psychological laboratory. After becoming professor, he first looked for general psychological laws, and later became interested in how people differ. Heymans investigated this question by studying biographies and collecting survey data. With this rigorous approach that far exceeded the standards of his time, he arrived at three basic dimensions in which people can vary in their temperament. This became the renowned ‘Heymans Cube’.Through decades of lectures for students and professors of all faculties, the theory became widely popular. This book provides a translation and adaptation of the original work, Heymans’ Inleiding tot de speciale psychologie (1929). The authors explain Heymans’ theory in an accessible way and make it come alive through illustrations inspired by the original text.