The field was named and defined by Bill Moggridge in the late 1980s, when he recognised that software was creating a new kind of designed experience — one that existed in time, not just in space. Unlike a poster or a building, software changes state in response to the user. This temporal dimension is what makes interaction design its own discipline, not a subset of graphic design.
The foundation of interaction design is feedback: the system must acknowledge every meaningful action the user takes. A button that gives no visual response when pressed is broken, even if the underlying function works correctly. The feedback loop — action, response, result — is the basic unit of interaction, and every breakage in this loop erodes trust.
The most advanced interaction design makes the computer disappear. Direct manipulation — where the user acts on objects, not on commands — is the ideal that touchscreens partially achieved and voice interfaces are still reaching for. The goal is always to reduce the cognitive distance between intention and result.