As Gero & Goel write in the preface to the Proceedings of the Third International Conference on Design Computing and Cognition: “There are now three sources for design research: design computing, design cognition and human-centered information technology. The foundation for much of design computing remains artificial intelligence with its focus on ways of representation and on processes that support simulation and generation. Artificial intelligence continues to provide an environmentally rich paradigm within which design research based on computational constructions can be carried out. Design cognition is founded on concepts from cognitive science, an even newer area than artificial intelligence. It provides tools and methods to study human designers in both laboratory and practice settings. It is beginning to allow us to test the claims being made about the effects of the introduction of novel technologies into the design processes in addition to helping us understand the act of designing itself. Human- centered information technology, the newest of the three areas, is concerned with the use of information technologies in communities of practice.” All three of the above perspectives are represented in the six papers in this special issue.