Do conscious perception and unconscious processing rely on independent mechanisms? A meta-contrast study

• We compare metacontrast-masking time course on direct and indirect perception measures.
• Direct and indirect measures of perception follow the same time course.
• Subjective and objective direct measures index the same conscious mechanisms.
• We demonstrate unconscious processing using response priming.
• Attention, not consciousness, determines the time course of metacontrast masking.

There is currently no consensus regarding what measures are most valid to demonstrate perceptual processing without awareness. Likewise, whether conscious perception and unconscious processing rely on independent mechanisms or lie on a continuum remains a matter of debate. Here, we addressed these issues by comparing the time courses of subjective reports, objective discrimination performance and response priming during meta-contrast masking, under similar attentional demands. We found these to be strikingly similar, suggesting that conscious perception and unconscious processing cannot be dissociated by their time course. Our results also demonstrate that unconscious processing, indexed by response priming, occurs, and that objective discrimination performance indexes the same conscious processes as subjective visibility reports. Finally, our results underscore the role of attention by showing that how much attention the stimulus receives relative to the mask, rather than whether processing is measured by conscious discrimination or by priming, determines the time course of meta-contrast masking.