Spreading Patterns examines how new constructions emerge and spread through the grammar of a language, in a process called "diffusion." This is done by tracking the development of three types of complements from the Middle English period to the present day. These are subject-controlled gerund complements, forELto-infinitives, and subject-controlled participial complements. In the first half of the book, De Smet focuses on how and why patterns diffuse. In the second half, which is largely corpus-based, De Smet tests his theoretical model of diffusion on the three complement types. His work demonstrates how diffusion interacts with the grammatical system of complementation, how diffusion proceeds, step-by-step, and why diffusion is directional.