Penguins jumping off a cliff, economic forecasters and financial advisors speculating against a currency, and farmers using traditional methods in India are all practising social learning. Such learning from the behavior of others may and does lead to herds, crashes, and booms. These issues have become, over the last ten years, an exciting field of research in theoretical and applied economics, finance, and in other social sciences. This book provides both an informal introduction and in-depth insights into the subject. Each chapter is devoted to a separate issue: individuals learn from the observations of actions, the outcomes of these actions, and from what others say. They may delay or make an immediate decision; they may compete against others or gain from cooperation; they make decisions about investment, crop choices, and financial investments. The book highlights the similarities and the differences between the various cases.

‘This book is a notable achievement. It is ambitious in scope, and provides substantive understanding of how different models in the area work. It offers a deep understanding of the range of validity of different conclusions in the literature and the relations between different possible model results. The general economist will find a rigorous and lucid in-depth introduction to the field. Even experts in the field will find here many challenges as well as enlightenment. Chamley’s book promises to be the key reference on rational models of social learning in economics for some time to come.’

David Hirshleifer - Ohio State University

‘Christophe Chamley brings the reader to the state of the art in formal modeling of social learning. His treatment of this burgeoning literature is extraordinarily clear and comprehensive. This book, by an author who has himself made major contributions to the subject, is destined to become a standard reference in the area.’

Sushil Bikhchandani Source: UCLA

‘Over the past decade there has been an explosion of interest in the field of social learning. Far from being a fad, this field is developing into one of the richest areas of economic research, with an ever-growing list of applications. Christophe Chamley has made profound contributions to the growth of the field, and presents us now with the definitive guide. His book is essential reading not only for graduate students, but also for current researchers trying to stay abreast of new findings. It helps us understand not only where the literature came from, but also where it is going.

Andrew Caplin Source: New York University

‘Chamley has chosen a topic of great interest to all academics in the social sciences. The tendency of human beings to conformity intrigues social psychologists and anthropologists, and the implications of mass behavior are important in politics, economics, and finance. Chamley fully understands this material and conveys it clearly in this book.’

Peter Norman Sorensen - University of Copenhagen