Students' capacity for making evaluative judgements of their own work is widely acknowledged as central to their learning within programmes as well as being vital to their subsequent professional practice. In higher education literature, the act of evaluative judgement is usually portrayed as a process of deliberative, analytical reasoning requiring student agency and objectivity, typically scaffolded by points of reference such as explicit criteria, rubrics or exemplars. This article challenges this common portrayal of judgement by drawing attention to research from outside higher education on the role of unconscious factors in judgement and decision-making. Drawing from the field of heuristics and bias studies, the article outlines six unconscious factors that have the potential to distort students' analytical judgement of their work. A recent challenge to the heuristics and bias approach that radically repositions the place of reasoning in judgement is also considered. Since these unconscious factors have received scant attention in higher education literature, the purpose of this article is to draw attention to them, to identify the challenges they pose to current understandings of evaluative judgement, and to outline their implications for enhancing assessment practice.