Examines some critical definitional and experimental-design problems that underlie the principles of knowledge of results (KR) and learning, the KR literature, and how newer principles of KR lead to notions of how KR works in human motor-learning situations. KR is defined as augmented feedback, where the KR is additional to those sources of feedback that are naturally received when a response is made. Transfer tests, usually under no-KR conditions, are essential for unraveling the temporary effects of KR manipulations from their relatively permanent learning effects. When this is considered, the literature reveals findings that produce reasonable agreement, although there are a number of inconsistencies in studies examining the same variables. When learning vs performance effects of KR are separated, a number of contradictions occur; new principles that emerge include the notion that KR acts as guidance, that it is motivating or energizing, and that it has a role in the formation of associations. It is suggested that KR may guide an S to the proper target behavior, with other processes (e.g., simple repetition) being the critical determinants of learning. (4 p ref) (PsycINFO Database Record (c) 2016 APA, all rights reserved)