Being able to judge the accuracy of one's work is an important facet of human decision making. Psychological investigation into self-assessment has stemmed largely from the experimental cognitive tra­dition and mainly concentrates on probabilistic accounts related to rational thinking. A major aspect of this work relates to the con­fidence exhibited by individuals when assessing their decisions, and is thus often referred to as the 'confidence paradigm'. Another per­spective has emerged in the last decade from the work of Differentia­lists. A robust outcome of these investigations is the existence of a 'confidence trait' that appears to be, at least in part, a determinant of the accuracy of self-assessment. The current work takes this per­spective further and examines alternative explanations for poor self-assessment. The outcomes suggest that are are a number of factors that determine accurate self-appraisal. These include question format, the difference between perceptual and cognitive tasks, gender and age. It seems that there is no single determinant of accurate self knowledge and many factors need to be accounted for when inter­preting experimental findings.