Originally published in 1919, this classic work of social psychology introduces the concept of the herd instinct in relation to human behavior and explores the fundamental importance of gregariousness among animals as well as among humans. In addition, author Wilfred Trotter incisively draws on the concept of social habit to provide a deeper understanding of the nature of human behavior as well as its affect on the national morale particularly in times of war. As Trotter noted in his original publication, these ideas may also be of use to a tired nation seeking peace.