Paul Fitts turned aimed movement into a measurable information-processing problem, and HCI researchers later used his law to compare pointing devices and reason about target size, distance, and interface layout.
Don Norman connected cognitive psychology with product and interface design, popularizing concepts such as affordances, mappings, feedback and conceptual models that shifted blame from users toward design.
Ben Shneiderman's theory of direct manipulation explained why visible objects, incremental actions and rapid reversible feedback made graphical interfaces feel easier to learn and control.