This document discusses the underlying psychology relevant to user experience (UX) design. It covers 5 aspects of psychology: 1) perception - how people group and make sense of visual elements, 2) motivation - what initiates and sustains human behavior, 3) emotion - how emotions can be positively or negatively influenced by design, 4) behavior - how to observe how people interact with interfaces, and 5) creativity and play - how everyone has creative abilities and games can engage users. The document emphasizes designing for human psychology rather than just for functionality.