A concise guide that explains how human perception, attention, memory, and decision-making affect interaction design and translates cognitive psychology findings into practical rules for creating usable interfaces. It covers principles such as visual grouping, affordances, feedback, constraints, Fitts’ and Hick’s laws, short-term memory limits, and error prevention, and shows how to apply them to reduce cognitive load, make actions visible and predictable, and support users’ mental models. The book emphasizes consistency, discoverability, and recoverability, offering actionable guidelines and examples to help designers create interfaces that align with human capabilities and limitations.