Forgotten variables in memory theory and research.
Memory research, like other scientific research, disregards many variables in order to bring the full force of the scientific method to bear on clearly important variables. The reasons why memory research attends to certain variables and disregards others emanate largely from theoretical assumptions that distinguish memory systems from other psychological systems, and that distinguish variables intrinsic to memory from those extrinsic to memory. Nevertheless, a number of these 'forgotten' variables affect memory performance. Regardless of past practice, it is a mistake for memory research to continue to ignore relevant variables. Doing so introduces measurement error that contaminates memory performance measures, and classification error that precludes the discovery of legitimate memory variables. It is proposed here that if forgotten memory variables are controlled, manipulated, and measured more extensively, then future memory research will have greater power and memory theories will have greater validity.