Animals commonly alter their behavior in the presence of other animals. This is particularly true in the context of aggressive exchanges, where individuals alter behavior to influence and form social relationships. Hierarchical relationships are widespread across taxa, yet the dynamic processes that produce them remain poorly understood. In particular, the exchange of information during fight interactions and how such information exchanges influences hierarchies remains elusive. In crayfish as in many other animals, dominance is thought to be primarily determined by physical superiority, where behavior and fight outcomes become predictable. However recent evidence has shown that aggressive encounters are dependent upon a myriad of factors outside of physical superiority and makes fight outcomes less predictable. This book provides an analysis of various extrinsic and intrinsic factors that influence fighting. Some of the variables examined include habitat preference, fluid flow, chemical signal use, previous social history, and neurochemical alterations. It also discusses how extrinsic and intrinsic factors are used to modify and maintain social hierarchies.