Measuring Perceptual Consciousness

Conscious perception is typically assessed with either objective or subjective measures (Seth et al., 2008). Measures are considered objective if conscious perception is estimated from performance in a discrimination task; inability to discriminate between stimuli is taken as evidence that participants had no conscious perception (Hannula et al., 2005).Measures are considered subjective if participants report their visual experience on each trial (Sergent and Dehaene, 2004; Del Cul et al., 2007). One type of subjective measures consists of metacognitive judgments; the relationship between metacognition and perceptual awareness is a matter of debate (Fleming and Lau, 2014; Jachs et al., 2015) and I will not discuss these measures further. Likewise, I will not discuss postdecision wagering approaches as they are affected by the participants’ risk aversion (Schurger and Sher, 2008). Proponents of subjective measures stress that objective measures (discrimination) provide only task performance and are not suitable for capturing visual experience (Lau, 2008). The major objection against subjective measures is contamination by response bias. Because it has been argued that participants can perform discrimination in the absence of perceptual awareness, many researchers currently favor subjective measures. In this paper, I show that objective measures (discrimination) and subjective measures (detection) are similar and both measure task performance. I further propose that task performance can be used as a valid measure of conscious perception.