The fastest algorithm in the world is useless if nobody can figure out how to use it. Human-computer interaction is the science of the space between the person and the machine — why some designs feel effortless and others make you want to throw your laptop across the room. It takes the fuzzy word "usable" and turns it into something you can design for, measure, and get right on purpose.
This branch covers interaction paradigms, usability and Norman's principles, the human perception,
cognition and memory that constrain every design, the UX design process, prototyping, and the
methods we use to evaluate a design — including