Confidence and accuracy, while often considered to tap the same memory representation, are often found to be only weakly correlated (e.g. Deffenbacher, 1980; Bothwell, Deffenbacher & Brigham, 1987). There are two possible (nonexclusive) reasons for this weak relation. First, it may be simply due to noise of one sort or another; that is, it may come about because of both within- and between-subject statistical variations that are partially uncorrelated for confidence measures on the one hand and accuracy measures on the other. Second, confidence and accuracy may be uncorrelated because they are based, at least in part, on different memory representations that are affected in different ways by different independent variables. In this article, we propose a general theory that is designed to encompass both of these possibilities and, within the context of this theory, we evaluate effects of four variables degree of rehearsal, study duration, study luminance, and test luminance in three face-recognition experiments. In conjunction with our theory, the results allow us to begin to identify the circumstances under which confidence and accuracy are based on the same versus on different sources of information in memory. In particular, we conclude the following. First, prospective confidence (assessed at the time of original study) and eventual accuracy are based on different sources of information: A sufficient description of these differences is that accuracy is determined by what we term memory strength, while prospective confidence is based both on memory strength and on a second dimension which we term memory certainty. Second, given identical test circumstances, retrospective confidence (assessed at the time of test) and accuracy can be considered to be based on the same source of information, memory strength. Third, degrading a picture at test can be construed as differentially affecting strength and certainty which, in turn produces different effects on confidence and accuracy. In a final section, we begin to explore the concept of memorial noise, which can be used as a central construct to explain patterns of between- and within-subjects confidence-accuracy correlations.