Card sorting (card sorting)
An information architecture technique where participants group content cards in whatever way makes sense to them, to uncover navigation structure and labelling. It can be open, when they create the categories; closed, when they sort into given ones; or hybrid. It tells you how people would group things, not whether the resulting structure works: tree testing answers that.
Choice overload (choice overload)
The idea that too many options paralyse rather than liberate. It is overstated and worth saying so: Iyengar and Lepper's famous jam study does not always replicate, and Scheibehenne and colleagues' meta-analysis found an average effect close to zero. It depends on the domain, on whether the person knows what they want, and on how the options are organised. Do not cut on dogma.
Chunking (chunking)
Merging several loose items into a single unit so they take up less room in working memory. A card number reads better in blocks of four than as sixteen digits in a row. Its limit: the chunk has to match what the user already knows. What is one unit to an expert is a hieroglyph to a novice.
Cognitive bias (cognitive bias)
The systematic error that results from applying a heuristic where it does not fit. Systematic means it repeats in the same direction, so it is predictable and you can design accounting for it. The other side matters just as much: biases operate on you while you research, not only on the user you are observing.
Cognitive load (cognitive load)
The mental effort you demand of a person to operate your interface. It rises when you force them to recall data from earlier steps, decode ambiguous groupings, or compare too many options. You do not lower it by reflexively stripping things out: you lower it by removing what does not serve the decision the person is making on that screen, right now.
Confirmshaming (confirmshaming)
The deceptive pattern that shames you for declining an offer: the decline button reads something like no, I would rather pay more. It is among the easiest to spot, which makes it a useful calibration case. When a pattern leaves you unsure, compare it against this one: a pre-ticked newsletter opt-in is far more arguable than obvious confirmshaming.
Contextual inquiry (contextual inquiry)
Observing the user where the action actually happens, not in a lab room. Beyer and Holtzblatt organise it into four principles, among them context and partnership under the master-apprentice model. It works because memory is fallible and people rationalise what they do: nobody mentions the password sticky notes on their monitor over a video call.