Consciousness and implicit memory trace for the unexpected stimulus in inattentional blindness

Inattentional blindness (IB) demonstrates that an unexpected stimulus (US) may be undetected when attention is engaged in a task. Previous studies using direct memory measurements relying on verbal report failed to find a memory trace for the US. Block (2011) suggested that contrary to Access Consciousness, Phenomenal Consciousness can exist without verbal report and attention. Mack and Rock (1998) found perceptual and semantic priming effects for the undetected US by using indirect memory tests. However, there are no items to be ignored in their paradigm. The present study aimed to show that the undetected US in an IB paradigm involving items to be ignored is processed and produces priming effects at the perceptual and semantic level. In Experiment 1, participants who were blind to the unexpected word were more likely to complete a single-solution word fragment with the US than the participants who were not exposed to the word. In Experiment 2, inattentionally blind participants were more likely to choose the picture for the unexpected word than the ones who were not exposed to the word. These two studies replicated previous findings in a paradigm with ignored items. The results showed that the undetected US is presumably processed at a phenomenally conscious level and produces perceptual and semantic priming effects on a subsequent task. The findings are also consistent with studies showing neural activations in the brain for the undetected US. The findings have implications for possible memory correlates of undetected visual information and for theoretical propositions regarding consciousness. Keywords: Inattentional blindness, priming, consciousness, word fragment completion, picture choice