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.