Metacognitive appraisals are essential for optimizing our information processing. In conflict tasks, metacognitive appraisals can result from different interrelated features (e.g., motor activity, visual awareness, response speed). Thanks to an original approach combining behavioral and electromyographic measures, the current study objectified the contribution of three features (reaction time [RT], motor hesitation with and without response competition, and visual congruency) to the subjective experience of urge-to-err in a priming conflict task. Both RT and motor hesitation with response competition were major determinants of metacognitive appraisals. Importantly, motor hesitation in absence of response competition and visual congruency had limited effect. Because science aims to rely on objectivity, subjective experiences are often discarded from scientific inquiry. The current study shows that subjectivity can be objectified.