The Four Waves of User-Centered Design

William Gribbons of the Design and Usability Center of Bentley University has written a piece for UX Magazine which describes his personal perspective on the history and evolution of user-centered design, a narrative which he organises into three distinct historical periods:

The First Wave: External Support
The Second Wave: Usable and Useful
The Third Wave: User Experience
The Fourth Wave: The Intersection of UX and Innovation

Gribbons analysis provides a useful way of thinking of the evolution of the paradigm from its functional origins to its more recent and all encompassing nature as an innovation paradigm.