The culmination of almost seven decades of research, A Trio of Pursuits: Puzzles in Human Development is the magnum opus of the career of Dr. Jerome Kagan, Emeritus Professor of Psychology, Harvard University, USA. This book summarizes three of the author's major research themes during a career that spanned from 1954 to present: preservation of individual traits, maturation of cognition and emotions, and the influence of two temperamental biases on personality. An introspective chapter on the deeper lessons learned by the author in research is also included, covering narratives such as the need to specify the context in which data are gathered, the need to supplement all self-reported data, studying puzzling observations rather than confirmation of a priori hypotheses, and avoiding the error of attributing psychological predicates to brain evidence. This book is a must-have for students and academics of Psychology and Cognitive Science, and may also be of interest to social scientists.