Approaching Consciousness with Masked Priming

Abstract

Masked Priming is an established paradigm to investigate consciousness. The impact of prime visibility on specific priming effects determines whether associated processes can occur independently of consciousness or might rely on consciousness. A meta-analytic review of 84 studies was conducted to assess the impact of prime visibility on effect sizes in interaction with various moderators (Chapter 2). A psychological model concerning the emergence of priming effects was proposed. Two main confoundings between moderators were identified. Specific task levels were predominantly applied with specific masking methods. Furthermore, temporal parameters were chosen differently between effect types. Subsequent experiments (Chapter 3) revealed that priming effects increase with increasing prime visibility when pattern masks are applied. Priming effects were independent of prime visibility with metacontrast masks. Pattern masks are thought to reduce prime visibility on an early level whereas metacontrast masks disturb recurrent processing. Lamme and Roelfsema (2000) previously proposed that recurrent processing characterizes consciousness. Perceptual and semantic priming effects were equally affected by variations in prime visibility. However, perceptual priming effects were generally larger than semantic priming effects. Further experiments were conducted to determine the courses of perceptual and semantic priming effects with increasing prime-mask SOA and mask-target SOA (Chapter 4). Priming effects generally increase with increasing prime-mask SOA and decline at long mask-target SOA. This decline seems to be based on a simple decay and active mechanisms of inhibition (e.g. Klapp, 2005). However, courses of perceptual and semantic priming effects with increasing mask-target SOA differed. This seems to be due to an additional mechanism of object updating that acts only with relevant masks (Lleras & Enns, 2004). In the current design, masks only activated the incongruent category (i.e. relevant masks) with perceptual congruency. An electrophysiological study was conducted to compare perceptual and semantic priming with identical stimulation (Chapter 5). The applied design allowed the estimation of behavioral priming effects without response association as well as effects on event-related potentials without response execution. Perceptual priming effects without response association were larger than semantic priming effects without response association. Furthermore, the P2 component and the P3(b) component were modulated through perceptual congruency. Semantic congruency was reflected in an N400-like effect with a delayed latency. Perceptual ERP effects were observed earlier and with different distributions than semantic ERP effects. Perceptual and semantic priming effects seem to be based on different mechanisms that share several attributes. However, the current work supports the idea of approaching consciousness through the comparison of different masking methods (cf. Breitmeyer, 2014).