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Poster B5, Wednesday, November 8, 3:00 – 4:15 pm, Harborview and Loch Raven Ballrooms

Neural tracking of attended continuous speech in monolinguals and early bilinguals

Andrea Olguin1, Tristan Bekinschtein1, Mirjana Bozic1;1University of Cambridge

A noisy acoustic background often surrounds speech and listeners have to isolate the target talker from the background in order to process a single speech stream. This selective attention results in stronger neural encoding of the attended speech envelope compared to the unattended one (Ding & Simon, 2014). A prominent but controversial hypothesis in the bilingualism literature states that knowing two languages leads to an enhancement in selective attention (e.g., Bak et al., 2014; Krizman et al., 2012, but see Paap et al., 2015), predicting that bilinguals will show different patterns of synchronisation between the neural activity and the attended speech envelope compared to monolinguals. We tested this hypothesis by tracking the neural encoding of attended continuous speech in monolinguals and early bilinguals in the context of different types of acoustic and linguistic interference. In the first study, 22 English monolinguals attended to a narrative in English presented to one ear, while ignoring interference presented to the other ear. Four different types of interference were presented to the unattended ear: a different English narrative, a narrative in a language unknown to the listener (Spanish), a well-matched non-linguistic acoustic interference (Musical Rain), and no interference. The neural activity was recorded by a dense array 128-channel EEG system and cross-correlated with the speech envelopes for both attended and unattended streams. Results showed that there was significantly more robust neural encoding for the attended envelopes than the ignored ones across all conditions. We also saw that the type of interference significantly modulated the encoding of attended speech, with the strongest encoding seen when the interference was in the same known language (English) and weakest when the interference was non-linguistic noise (Musical Rain). Unattended linguistic interference (in both English and Spanish) was encoded more strongly than the unattended non-linguistic noise, suggesting that different types of interference trigger different depths of processing analysis. The second study carried out the same dichotic-listening paradigm on 22 early Spanish-English bilinguals. Participants were instructed to attend to a narrative in Spanish presented to one ear, while ignoring one of four different types of interference presented to the unattended ear: a different Spanish narrative, a narrative in a language unknown to the listener (Serbian), non-linguistic acoustic interference (Musical Rain), and no interference. Equivalent analyses showed a different pattern of results to that observed in monolinguals: early bilinguals appear to encode the attended and unattended streams equally when they are both in their native tongue (Spanish), but behave comparably to monolinguals with other types of interference. Taken together, these results demonstrate that top-down selective attention differentially modulates envelope encoding in early bilinguals and monolinguals. They will be discussed in the context of the relevant theories of selective attention and bilingualism.

Topic Area: Control, Selection, and Executive Processes

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