What I thought were the core concepts:
- Human-centered design: the principle of putting human needs, abilities, and psychology first, letting the design and technology follow to accommodate those realities. "It is the duty of machines and those who design them to understand people. It is not our duty to understand the arbitrary, meaningless dictates of the machines."
- Discoverability: a critical aspect of design, which is the ability for the user to figure out how to use a device and what the possible actions are. It consists of five main components:
- Affordances—The relationship between an object and the specific user's ability to use that object. For example, the flat surface of a bench affords sitting (this happens to be a visible affordance) but the weight (invisible) of the bench affords carrying only to those strong enough to do so. An affordance is not a specific property of an object indicating usage; that would be a signifier.
- Signifiers—The characteristics of an object that signal to the user where or how actions should occur. "Affordances determine what actions are possible. Signifiers communicate where the action should take place. We need both."
- Constraints—Interactions can be guided by taking advantage of physical, logical, semantic, and cultural limitations on what is possible or what makes sense.
- Mappings—The relationship between controls and their outcomes. The easiest mappings are when the control is directly on the item to be controlled, the worst case is in situations like a row of light switches in an auditorium, where there is usually no way to figure out what switch controls what light before trial and error.
- Feedback—A response to know the system is working on a command. For example, elevator buttons without lights get pushed repeatedly by people who had no idea if it has already been pushed or if their push was registered.
|Principles of the double-diamond model of design. (Source, though it's not clear who made this originally. This concept was first introduced in 2005 by the British Design Council.)|
Some more concepts I found interesting:
- Who is to blame? Usually bad design. People often blame themselves for not being able to use a device properly when really the root cause is a poorly-designed device. The problem can be so pervasive that even the designers blame themselves for mistakes when testing the products! "Humans err continually; it is an intrinsic part of our nature. System design should take this into account."
- A story of investigating a failure at a nuclear power plant: "The operators were blamed for these failures: 'human error' was the immediate analysis. But the committee I was on discovered that the plant's control rooms were so poorly designed that error was inevitable: design was at fault, not the operators."