Inferences about consciousness using subjective reports of confidence

Metacognition, or "knowing that you know", is a core component of consciousness. Insight into a perceptual or conceptual decision permits us to infer perceptual or conscious knowledge underlying that decision. However when assessing metacognitive performance care must be taken to avoid confounds from decisional and/or confidence biases. There has recently been substantial progress in this area and there now exist promising approaches. In this chapter we introduce type I and II signal detection theory (SDT), and describe and evaluate signal detection theoretic measures of metacognition. We discuss practicalities for empirical research with these measures, for example, alternative methods of transforming extreme data scores and of collecting confidence ratings, with the aim of encouraging the use of SDT in research on metacognition. We conclude by discussing metacognition in the context of consciousness.