An ERP investigation of accented isolated single word processing

Previous studies show that there are differences in native and non-native speech processing (Lev-Ari, 2018). However, less is known about the differences between processing native and dialectal accents. Is dialectal processing more similar to foreign or native speech? To address this, two theories have been proposed. The Perceptual Distance Hypothesis states that the mechanisms underlying dialectal accent processing are attenuated versions of those of foreign (Clarke & Garrett, 2004). Conversely, the Different Processes Hypothesis argues that the mechanisms of foreign and dialectal accent processing are qualitatively different (Floccia et al, 2009). The present study addresses these hypotheses. Electroencephalographic data was recorded from 25 participants who listened to 40 isolated words in different accents. Event-Related Potential mean amplitudes were extracted: P2 [150-250 ms], PMN [250-400 ms] and N400 [400-600 ms]. Support for the Different Processes Hypothesis was found in different time windows. Results show that early processing mechanisms distinguish only between native and non-native speech, with a reduced P2 amplitude for foreign accent processing, supporting the Different Processes Hypothesis. Furthermore, later processing mechanisms show a similar binary difference in the processing of the accents, with a larger PMN negativity elicited in the foreign accent than the others, further supporting the Different Processes Hypothesis. Results contribute to the understanding of single word processing, in which it is uniquely difficult to extract acoustic characteristics from foreign accent, and in which foreign accented speech is associated with the largest cost, as compared to native and dialectal speech, of phonological matching between representations and acoustic input. Highlights Accent affects early speech processing mechanisms at the level of the isolated word Acoustic characteristic extraction is more difficult for foreign-accented speech Phonological normalization of foreign-accented speech is uniquely difficult Accent no longer affects later speech processing mechanisms at the isolated word