The N400 component reflecting semantic and repetition priming of visual scenes is suppressed during the attentional blink.

In the attentional blink paradigm, participants attempt to identify two targets appearing in a rapidly presented stream of distractors. Report accuracy is typically high for the first target (T1) while identification of the second target (T2) is impaired when it follows within about 200-400 ms of T1. An important question is whether T2 is processed to a semantic level even when participants are unaware of its identity. We examined this issue in three studies that used natural scenes as stimuli and the N400 component of the event-related potential (ERP) as a measure of semantic priming. In the first experiment, the prime (e.g., a doghouse in a yard) was presented at the beginning of the trial and a test picture that was related (e.g., a dog standing in the kitchen) or unrelated (e.g., a coffee mug on a table) appeared as T2. In the second experiment, the prime was presented as T2 and the test picture appeared at the end of the picture sequence. In both experiments, we found robust semantic priming when participants were aware of the identity of the blinked picture and an absence of priming when they were unaware. In Experiment 3, we used identity priming to assess whether earlier representations preceding semantics were preserved, and again found that priming critically depended on awareness of the prime's identity. These results suggest that semantic priming in scenes, as measured with the N400, is a higher-level process that critically depends on attention and awareness.