Manuscript received March 28, 2000; revised February 20, 2001. Recommended
by Guest Editor N. Xi. This work was supported in part by British
Telecom, Things That Think consortium at the M.I.T. Media Laboratory,
Steelcase NA, a Research Grant from Purdue Research Foundation, and by a
National Science Foundation Faculty Early Career Development (CAREER)
Award under Grant 9984991-IIS.
H. Z. Tan and L. A. Slivovsky are with the Haptic Interface Research
Laboratory, Purdue University, West Lafayette, IN 47907 USA (e-mail:
hongtan@purdue.edu; lynnes@purdue.edu).
A. Pentland is with the Media Laboratory, Massachusetts Institute of Technology,
Cambridge, MA 02139 USA (e-mail: sandy@media.mit.edu).
Publisher Item Identifier S 1083-4435(01)08147-9.