The effects of attention and task-relevance on the processing of syntactic violations during listening to two concurrent speech streams

Abstract

The notion of automatic syntactic analysis received support from some event-related potential (ERP) studies. However, none of these studies tested syntax processing in the presence of a concurrent speech stream. Here we present two concurrent continuous speech streams, manipulating two variables potentially affecting speech processing in a fully crossed design: attention (focused vs. divided) and task (lexical - detecting numerals vs. syntactical - detecting syntactic violations). ERPs elicited by syntactic violations and numerals as targets were compared with those for distractors (task-relevant events in the unattended speech stream) and attended and unattended task-irrelevant events. As was expected, only target numerals elicited the N2b and P3 components. The amplitudes of these components did not significantly differ between focused and divided attention. Both task-relevant and task-irrelevant syntactic violations elicited the N400 ERP component within the attended but not in the unattended speech stream. P600 was only elicited by target syntactic violations. These results provide no support for the notion of automatic syntactic analysis. Rather, it appears that task-relevance is a prerequisite of P600 elicitation, implying that in-depth syntactic analysis occurs only for attended speech under everyday listening situations.

Linguistic predictability influences auditory stimulus classification within two concurrent speech streams

“…The ERP effects of attention were fully compatible with those found in previous studies on auditory attention (see, e.g., Patel & Azzam, ; Szalárdy et al, ; Szalárdy, Bőhm, Bendixen, & Winkler, ). N2 and P3 amplitudes were higher for targets than distractors.…”

“…Thus, the current results suggest that segregating the concurrent speech streams was affected by linguistic processes and that stream segregation interacted with target identification. The N2b is not elicited by unattended sounds (see, e.g., Szalárdy et al, ; Tong & Melara, ). Therefore, the N2 elicited by distractors either reflects that listeners switched to the unattended stream from time to time, and thus, actively detected the coughs or that the distractor N2 is a mismatch negativity (MMN, for a review, see Näätänen, Paavilainen, Rinne, & Alho, ) which is elicited by rare stimuli deviating from some regular aspect of the majority of the stimulation.…”

Attention and speech-processing related functional brain networks activated in a multi-speaker environment

“…Fig 3 shows a summary of the behavioral measures. The behavioral results have also been described in the paper reporting the ERP effects [68]. For the effects of stream location on the performance measures, see S7 File.…”

“…Further, the lack of differentiation between the two types of detection tasks may also indicate that extracting and manipulating certain lexical and grammatical speech features may rely on largely overlapping neural networks. However, event-related phasic neural activity usually distinguishes these two aspects of speech [68,84,85] (. The networks showing significant effects of task type in our study are represented along their timescales and neuro-anatomical characteristics on Fig 6.…”

“…Although longer epoch length generally results in lower connectivity values [66,67], this should not affect the contrasts tested in the study. Epochs including detection task targets or a button press were rejected from further analysis (note that the event-related brain potentials are reported separately: [68]. Epochs with an amplitude change exceeding 100 μV at any electrode were also rejected (Fig 2A).…”