It turned out to be a program in teaching machines and related technologies. I am a professor extensively involved in research and development related to second generation instructional design. See the ID2 Web site for the mission statement of second generation instructional design. In the pursuit of this question I have explored research in learning, instructional strategies, and knowledge analysis. This research has been both experimental and design research.
Design research is the invention of artifacts to solve problems.
In my case these artifacts take the form of instructional design systems. My research question led me to the field. My PHD program prepared me with some of the tools necessary to pursue this research question. I continue to pursue this question after 34 years of academic career and hope to pursue this question for the next 20 years. See the research papers section of the ID2 web site.