Replicability of neural responses to speech accent is driven by study design and analytical parameters

Abstract

Recent studies have reported evidence that listeners' brains process meaning differently in speech with an in-group as compared to an out-group accent. However, among studies that have used electroencephalography (EEG) to examine neural correlates of semantic processing of speech in different accents, the details of findings are often in conflict, potentially reflecting critical variations in experimental design and/or data analysis parameters. To determine which of these factors might be driving inconsistencies in results across studies, we systematically investigate how analysis parameter sets from several of these studies impact results obtained from our own EEG data set. Data were collected from forty-nine monolingual North American English listeners in an event-related potential (ERP) paradigm as they listened to semantically congruent and incongruent sentences spoken in an American accent and an Indian accent. Several key effects of in-group as compared to out-group accent were robust across the range of parameters found in the literature, including more negative scalp-wide responses to incongruence in the N400 range, more positive posterior responses to congruence in the N400 range, and more positive posterior responses to incongruence in the P600 range. These findings, however, are not fully consistent with the reported observations of the studies whose parameters we used, indicating variation in experimental design may be at play. Other reported effects only emerged under a subset of the analytical parameters tested, suggesting that analytical parameters also drive differences. We hope this spurs discussion of analytical parameters and investigation of the contributions of individual study design variables in this growing field.

A 10-hour within-participant magnetoencephalography narrative dataset to test models of language comprehension

“…Our participants were speakers of three distinct English dialects (UK, US and South African English). While this could be a potential source of inter-participant variability in neural responses, the nature of out-group accent effects in M/EEG remains debated 60 . Importantly, we speculate that accent-driven variability is less of an issue for the current dataset where two participants listened to an out-group dialect (British English) where the lack of exposure, we reason, was likely not critical.…”

Recognition of foreign-accented vocoded speech by native English listeners

“…In addition to the behavioral data, a handful of studies used event-related potentials (ERP) to examine the impact of talkers' accents on lexical and semantic processing [44][45][46][47][48]. Although researchers reported inconsistent results regarding the direction of change of relevant EPR components induced by semantic and/or grammatical violations, which might be partially accounted for by the variations in research design and/or data analysis procedures (see [49] for a review), the important common finding relevant to the present study is that talkers' foreign accents can influence various levels of speech processing including lexical access, semantic integration, grammatical processing, etc.…”