19 nov Metacognitive approach to phenomenal and access consciousness19 nov 2012
Speaker: Ryota Kanai, University of Sussex
In many circumstances, conscious perception fails despite activations of relevant brain regions by subliminal visual presentation. Conceptually, failure to register a stimulus in awareness could be attributed to suppression of early sensory signals (perceptual blindness) and/or failure of attention to register suprathreshold signals (attentional blindness). However, these two types of failure of awareness are difficult to distinguish behaviourally because in both cases, observers would report the absence of conscious percepts. To distinguish these two types of subjective blindness, we have previously developed a metacognitive framework called subjective discriminability of invisibility, which is derived from the so-called Type 2 signal detection framework (Kanai, Walsh & Tseng, 2010 in Consciousness & Cognition). This new analysis method distinguishes blindness due to signal reduction such as lowering of contrast, backward masking and interocular suppression as perceptual blindness, whereas it classified reduction of visibility due to attentional distraction, attentional blink and enhanced spatial uncertainty as attentional blindness. Moreover, when we explicitly manipulated decision criterion by changing the likelihood of target present trials, the percentage of target misses increases. When the blindness induced by criterion shift was induced by conservative criterion, the same experimental paradigm shifted from perceptual blindness to attentional blindness. The relevance of these findings for philosophical concepts of phenomenal and access consciousness will be discussed.
Location : Salle de réunion du LPP, H432, Centre Biomédical des Saints-Pères, 45 rue des Saints-Pères, 75006 PARIS