Expectancy effects in the EEG during joint and spontaneous word-by-word sentence production in German

Tatiana Goregliad Fjaellingsdal,Diana Schwenke,Anna K Kuhlen,Joost Meekes,Martin G Bleichner,Sara Bögels,Stefan Scherbaum

doi:10.1038/s41598-020-62155-z

Abstract

Our aim in the present study is to measure neural correlates during spontaneous interactive sentence production. We present a novel approach using the word-by-word technique from improvisational theatre, in which two speakers jointly produce one sentence. This paradigm allows the assessment of behavioural aspects, such as turn-times, and electrophysiological responses, such as event-related-potentials (ERPs). Twenty-five participants constructed a cued but spontaneous four-word German sentence together with a confederate, taking turns for each word of the sentence. In 30% of the trials, the confederate uttered an unexpected gender-marked article. To complete the sentence in a meaningful way, the participant had to detect the violation and retrieve and utter a new fitting response. We found significant increases in response times after unexpected words and – despite allowing unscripted language production and naturally varying speech material – successfully detected significant N400 and P600 ERP effects for the unexpected word. The N400 EEG activity further significantly predicted the response time of the subsequent turn. Our results show that combining behavioural and neuroscientific measures of verbal interactions while retaining sufficient experimental control is possible, and that this combination provides promising insights into the mechanisms of spontaneous spoken dialogue.

Highlights

The exchange between two persons conversing is stunningly fast: interlocutors take turns speaking and listening at a rapid rate, requiring them to produce and process language simultaneously
In the word-by-word task, participants successfully produced a sentence without grammatical errors and with the predefined verb and object in more than 98% of all trials
Errors were predominantly present in the first of the twelve blocks, indicating a familiarization effect over the experiment and/or problems of the participant understanding the task of constructing a correct sentence

Summary

Introduction

The exchange between two persons conversing is stunningly fast: interlocutors take turns speaking and listening at a rapid rate, requiring them to produce and process language simultaneously. A high degree of coordination is necessary, as the interacting partners have to adapt to each other turn-by-turn in order to produce a meaningful sentence We believe this level of coordination is achieved by forming expectations about the partner’s utterance. We measure the underlying electrophysiological activity while systematically manipulating whether the participants’ expectations are met or not For this purpose, we make use of pictures showing objects that have more than one naming option, i.e., synonyms, with different gender-marked articles in German. The confederate inserted unexpected sentence continuations (i.e., articles of unexpected gender), where the participant had to process the unexpected event and needed to retrieve and produce a new response deviating from his or her preferred object name

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Discussion

Conclusion