There are an enormous number of people whom I depended on while working on this thesis. Firstly I thank my thesis committee; Roz, who has patiently contributed so much to this thesis that I consider the work to be ours more than mine; Chris Csikszentmihályi whose keen criticism and levity emboldened this work; and Caspar Hare for his energetic discussions and receptivity to unorthodox approaches. Each made this thesis possible in their own individual manner.

I'd additionally like to thank Linda Peterson, Hiroshi Ishii, Daniel Goroff, Lynne Lenker, Kevin Davis, Nia Lewis, Pat Solakoff, and Sile O'Modhrain for facilitating this thesis in a myraid of different ways. Contributions from the Things That Think and Digital Life consortia at the MIT Media Lab, the National Aeronautics and Space Administration, and National Science Foundation (ITR # 0325428) provided financial support for this work.

This thesis really catalogs the hard work of a number of individuals who contributed many of the ideas discussed. Marc Strauss has spent many long hours debugging and improving devices used in this thesis. Phil Davis's collaborative efforts for the experimental portion of this thesis provided refinements and many good ideas. I would like to thank Dan Ariely and Nina Mazar for providing a starting point and suggestions for the Quiz protocol. Jussi Angesleva's work on EmoteMail provided a quintessential example and starting point for this work. Michael Ananny diligently looked over formative drafts and outlines of this thesis. Ross O'Neil hand soldered several of the earliest prototypes. Stephen Hughes, Scott Eaton, and Gary McDarby provided electrical engineering expertise for many of the early prototypes. Tad Hirsch worked through some of the first skin conductance circuits. Keith Battocchi redesigned the pressure mouse using surface-mount technology. Win Burleson's and Kyoung Park's work provided an excellent example of how the devices described in this thesis could be used in practice.

Additionally, both the Affective Computing and MindGames groups provided copacetic environments in which to pursue this work. Thanks for all the help from Ashish Kapoor, Raul Fernandez, Alan Qi, Jay Silver, Jocelyn Scheirer, Jennifer Healey, Shaundra Daily, Hyungil Ahn, Tim Bickmore, Charles Du, Karen Liu, and Akshay Mohan. Additionally thanks to Morgan Brickley, David Coyle, Damini Kumar, Ed Lalor, Marc Matthews, John Sharry, Robert Burke, Darran James Condron, Daragh McDonnell, and Philip McDarby. Many other folks from around also helped in variety of ways: Elisabeth Sylvan, Anmol Madan, and John Maeda. I would like to thank David Farkas and Mary Coney for providing much encouragement when I was an undergraduate.

There are a good number of people who kept me sane or just kept me company during the long and sometimes vexing process of getting a Ph.D.: (Coloradoans) Marshall Smith, Roger Squire (Bostonians) Courtney Humphries, Greg Harfst, Steven Richman, Ali Rahimi, Paul Nemirovsky, Dimitris Vyzovitis, Cameron Marlow, Chris Wren, Yuri Ivanov, Nick Feamster, Claire Monteleoni, Matt Smith, Marie Titus, Aisling Kelliher, Andrew Nevins, Ramesh Srinivasan, Lisa Brewer, Kerstein Audette, Jessica Hinel, Ben Recht, Kevin Allison, James Patten, Jeana Frost, Nicole Justis, Emma Brunskill, Lauren Faria (Dubliners) Valentina Nisi, Arianna Basoli, Marije Kanis, Enrico Costanza, Andrea Chew, Cati Vaucelle, David Reitter, Kim Gomez, Herve Gomez, Philippe Duval, Jonah Brucker-Cohen, Katherine Moriwaki, Matt Karau, Niall Winters, Renee Hall, Alison Wood, Michael Lew, Roberta Cianetti, Lily Shirvanee, Jennica Falk (Climbers) Aryesh Mukherjee, Jen Wang, Mike Lambert, Sam Roweis, Dan Shub, Solar Olugebefola, Jesse Berwald (New Yorkers) Matt Norwood, Joshua Schachter (Elsewhere) Alvaro Cassinelli, Susan Pearlman, Stoffel Kuenen, Michelle Peterson, Yin Chao, Daryl Carlson, Donna Coppola, Ben Piper, and (of course) my family.

I send my love to Mom, Dad, Justin, Jay, Scottie, and Joelle.

This thesis is dedicated to my paternal grandfather.