• Chair, Department of Cognitive Science, Johns Hopkins University, Jan. 1997 - June 1998 (Acting), July 1998 - June 2000.
  • Full Professor, Department of Cognitive Science, Johns Hopkins University, 1994-present.
  • Adjunct Professor, Department of Linguistics, University of Maryland at College Park, 1994-present.
  • Faculty, Center for the History and Philosophy of Science, Johns Hopkins University, 1995-present.
  • Assistant Director, Center for Language and Speech Processing, Johns Hopkins University, 1995-present.
  • Director, NSF IGERT Training Program in the Cognitive Science of Language, 1999-2004.

  • Professor, Department of Computer Science, University of Colorado at Boulder,
      • Full Professor, 1994-95 (on leave, 1994-95).
      Associate Professor, 1990-94.
      Assistant Professor, 1985-90.

  • Assistant Research Cognitive Scientist (Assistant Professor - Research), Institute for Cognitive Science, University of California at San Diego, 1982-85.
  • Visiting Scholar, Program in Cognitive Science, University of California at San Diego, 1981-82.
  • Faculty, Summer School in Linguistics, Girona, Spain, 2000.
  • Faculty, First International Summer Institute in Cognitive Science, SUNY Buffalo, 1994.
  • Faculty, Linguistic Institute, University of California at Santa Cruz, 1991.
  • Faculty, Connectionist Models Summer School; Carnegie?Mellon University, 1986, 1988; University of California, San Diego, 1990; University of Colorado, Boulder, 1993.
  • Faculty, Advanced Course in Artificial Intelligence, Neuchâtel, Switzerland, 1989.
  • Consultant, Xerox Palo Alto Research Center, Intelligent Systems Laboratory, 1987.
  • Visiting Scholar, Linguistic Institute, Stanford University, 1987.

  • National Science Foundation, John H. Edwards, and Indiana University Graduate Fellow, 1976-81.
  • Associate Instructor, Department of Physics, Indiana University, 1976-81.
  • Project Specialist, Institute for Research on Poverty, University of Wisconsin, 1978.
  • Consultant, California Planning and Conservation Foundation, 1975.
  • Undergraduate Teaching Assistant, Committee on Natural Sciences, Harvard University, 1974-75.