In his book The Art of Interactive Design: A Euphonious and Illuminating Guide to Building Successful Software, Chris Crawford clarified the term ‘interact’ from ‘react’ and ‘respond’. Interaction is a cyclic process involves input, process and output, and it can be between human to human, or human with machine.

Then what exactly is ‘Physical Interaction’? In this context I consider ‘physical’ as human body, more precisely, the human physical system including our input reception parts such as ears, eyes, and mouth, the neural system and blood circulation as network, our brain as CPU, and our month and moves as output. Does this mean that we as a person, can interact with ourselves? Not exactly. In most cases, different parts of our body work with each other as a responsive way, but not interactively. Seeing a roast duck (input) and your mouth start to be filled with saliva (output), this is because you remember how delicious it tastes (process). This is a responsive act, not interaction, even when there is another person involved that describing the duck. This is because one distinction between these two is that ‘interact’ involves thinking and interaction is a sequence of ‘PURPOSELY’ moves.

Sometime ‘purpose’ define a act as interaction, coordination or participation. Take dancing as an example, when it is a group dancing as a team, people do pay attention to each other’s position and moves.But this is coordination rather than interaction, because the purpose of information exchange is to coordinate for synchronization. In another case, when people dancing in a ball to socialize, such act is truly a ‘physical interaction’ involving sound, image, touch, and conversations. Therefore I define ‘physical interaction’ as ‘a meaningful responsive process to meet a certain purpose’. A good physical interaction will enhance or amplify our experience, and fulfill our purpose in a better (quicker, easier, funnier, prettier…) way.


In Bret Victor’s video on future interaction technology, it reveals how our daily life experience can be enhanced with physical interaction technology. Especially it shows how technology can improve the experience for a defined purpose. It is important to understand the use cases and how people interact with information, with machine, and with other people for introduction, guidance, communication, and collaboration. To conclude, a deep understanding of the PURPOSE of a physical interaction is a crucial foundation to start a good design.