Physical Computing Week 1: What is physical interaction?

Following Crawford’s definition of interaction as an iterative cycle of listening, thinking, and speaking, good physical interaction entails an object that can listen well, think well, and speak well. I will focus on the listening and speaking parts, as they are easier to evaluate empirically.

Listening well means capturing user input fast and in a granular way. The speed at which virtual reality headset tracks orientation can make or break the immersiveness of one’s experience in a virtual world. The degree of granularity of a MIDI keyboard (meaning its velocity, pressure, or displacement sensitivity) has a profound effect on the expressiveness of the instrument. Additionally, as Bret Victor points out in “A Brief Rant on the Future of Interaction Design,” good physical interaction ideally involves making rich use of existing human capabilities. A steering wheel controller engages the hands in a more familiar manner than a gamepad, even if the two might be otherwise equivalent in terms of the actions they allow.

Speaking well means providing output that contributes meaningfully to the “conversation” (to borrow Crawford’s metaphor) at hand. The output needs to be clear enough to direct the interaction forward: a transparent cup provides better interaction than an opaque one because it gives one an immediate, visual answer to the question of how much liquid is left in the cup, prompting the appropriate course of action (drinking or refilling). Good interaction also ideally involves a degree of surprise: it’s hard for a user to have a memorable experience with a physical interface if they can always anticipate its responses.