Humans may run faster, read less, or type more quickly, simply because someone else is present. The presence of one person affects the behaviour of another: this is known as social facilitation and is one of the oldest topics in social psychology. Despite its importance this is the first book-length study of the phenomenon. Dr Guerin reviews all work in the area from 1898 onwards, looking at both animal and human research, and develops his own theory, based on modern behaviour analysis. The book will be appreciated for its wide-ranging and balanced review of previous work on social facilitation and for the general review of the state of social psychology today that Dr Guerin’s work on the phenomenon includes. The author’s theoretical stance is also innovative and important, and will make the work required reading.