Human-computer interaction

All systems where a human interacts with a machine. This encompasses software and websites, mobile applications, the interfaces of embedded systems such as a car, a plane or medical equipment, as well as voice and gesture commands. HCI covers a broad spectrum, from the most everyday interface to the most specialised.

Affordance refers to the ability of an interface element to signal the way it should be used. A raised button indicates that you can press on it; underlined and coloured text indicates a link. These affordances help the user understand the interface without having to learn it. The concept comes from the psychologist James Gibson, and it was Don Norman who applied it to the design of objects and interfaces.

Through expert frameworks first, such as Nielsen's ten heuristics or the criteria of Bastien and Scapin, for a methodical evaluation. Through user-centred methods next, tests and questionnaires, which gather what users actually feel. An HCI is generally judged on three dimensions: its effectiveness (reaching the goal), its efficiency (the effort required to reach it), and the satisfaction it provides.

HCI is the historical field that studies the interaction between humans and machines, born with computer science and ergonomics. UX design is a more recent development of it, centred on the user's overall experience, their emotions and their usage, beyond the interface alone. UX builds on what HCI established, widening the view from the device to the person.

No. The screen is only one modality among others. An HCI can rely on voice, gesture, touch, sound, or physical controls such as buttons and levers. In critical systems, a cockpit or a control room, these non-visual modalities are often essential, because they leave the eyes free to monitor something else.