and explore the biographies, complex relations and social networks between members of the movement. Using principles derived from embodied cognition, cognitive load theory, and embodied design TUIs have been shown to increase learning performance by offering multimodal feedback. However, these benefits for learning require forms of interaction design that leave as much cognitive capacity as possible for learning. Physical icon A physical icon, or phicon, is the tangible computing equivalent of an icon in a traditional graphical user interface, or GUI. Phicons hold a reference to some digital object and thereby convey meaning. History Physical icons were first used as tangible interfaces in the metaDesk project built in 1997 by Professor Hiroshi Ishii's tangible bits research group at MIT. The metaDesk consisted of a table whose surface showed a rear-projected video image. Placing a phicon on the table triggered sensors that altered the video projection. See also Hardware interface Kinetic user interface Natural user interface Organic user interface Unconventional computing References External links TUIO open framework for tangible multitouch surfaces at TUIO.org Encyclopedia entry on the history of Tangible Interaction and Tangible User Interfaces White paper on The Evolution of Tangible User Interfaces on Touch Tables User interfaces User interface techniques Surface computing