A. INTRODUCTION AND BACKGROUNDl,2 This report reviews and interprets research on the nature and magnitude of the effects of those factors which influence how well knowledge and skills (K&S) are retained over relatively long periods of nonuse. Our interest lies in the kinds of knowledge domains and skills that military personnel must master to function effectively on their jobs. The practical concern impelling this study is that K&S degradation or loss (which we will refer to as "decay") can and does occur, often and severely enough, to jeopardize military preparedness. There are occasions in...