ERP signatures of conscious and unconscious word and letter perception in an inattentional blindness paradigm

•An inattentional blindness paradigm with word form stimuli was combined with ERPs.•Words and consonant strings helped test for orthographic and lexical processing.•A 3-phase design helped separate awareness of word forms from task-based reporting.•ERPs suggest orthographic but not lexical processing during inattentional blindness.•VAN correlated closely with awareness, while P3b correlated with the reporting task.

A three-phase inattentional blindness paradigm was combined with ERPs. While participants performed a distracter task, line segments in the background formed words or consonant-strings. Nearly half of the participants failed to notice these word-forms and were deemed inattentionally blind. All participants noticed the word-forms in phase 2 of the experiment while they performed the same distracter task. In the final phase, participants performed a task on the word-forms. In all phases, including during inattentional blindness, word-forms elicited distinct ERPs during early latencies (∼200-280 ms) suggesting unconscious orthographic processing. A subsequent ERP (∼320-380 ms) similar to the visual awareness negativity appeared only when subjects were aware of the word-forms, regardless of the task. Finally, word-forms elicited a P3b (∼400-550 ms) only when these stimuli were task-relevant. These results are consistent with previous inattentional blindness studies and help distinguish brain activity associated with pre- and post-perceptual processing from correlates of conscious perception.