Neural markers of speech processing during inattentional deafness☆

Cognitive scientists have long debated the capabilities of non-conscious perception, defined as the level of processing of external stimuli that people do not consciously experience. While much is known about non-conscious visual perception, the auditory modality has received less focus. Here, we examine the level of processing for audible and intelligible spoken words that participants did not notice while performing another difficult visual task. Using repeated occurrences of such inattentional deafness and awareness probes, we measure the non-conscious processing of undetected words. In two pre-registered EEG experiments (N = 67), detected words elicited a frontal followed by a parietal scalp positivity, compared to matched pseudowords. Undetected words, however, showed frontal positivity compared to pseudowords, which differed in distribution and latency from the response to detected words. An exploratory analysis revealed a behavioral interference of undetected words with visual task performance. Both markers of non-conscious processing were contingent on relevance, implying that auditory non-conscious processing is automatic yet goal-dependent. Overall, our results support flexible capabilities for non-conscious speech perception, consistent with the ability to integrate acoustic information over time.