Cognitive processes involved in turn-taking within Dutch question-answer sequences: An EEG-study

In experimental psycholinguistics, research has focused overwhelmingly on either language comprehension or language production. However, the ultimate goal should be to identify the cognitive mechanisms that occur during the actual use of comprehension and production in everyday life, for example in conversation. Turn-taking (Sacks, Schegloff, & Jefferson, 1974) and action-sequencing (Schegloff, 2007) are essential mechanisms in everyday communication, but have not been studied much yet in the domain of experimental psycholinguistics (but see De Ruiter, Mitterer, & Enfield, 2006; Magyari & De Ruiter, 2012; Roberts, Francis, & Morgan, 2006). CA, on the other hand, has focused extensively on these mechanisms, via observing the behavior of conversationalists. To bring these two research domains closer together, in the present study, we aim to look at the cognitive processes that form the foundations for observable turn-taking and action-sequencing behavior in social interaction. We used electroencephalography (EEG), a method that measures electrical brain activity with a very good time resolution, to address this question. In EEG, experimental control is necessary to identify patterns of brain activity related to specific cognitive processes. Using an interactive quiz paradigm in Dutch, we investigated the processes underlying turn-taking in question-answer sequences, while still exerting enough experimental control over both the presented questions and expected answers. Participants were asked quiz questions by a research assistant while their EEG was measured. These questions were in fact pre-recorded, but participants believed they were asked live and they did receive live feedback from the assistant. We compared 'early questions' such as "Which character, also called 007, appears in the famous movies?" in which answer planning could start early in the question (at "007") with matched 'late questions' like "Which character from the famous movies, is also called 007?" in which answer planning could only start at the last word. Reaction times were longer for answers ("James Bond") to late than to early questions. Averaging the EEG signal to the critical word ("007" in the example) in both types of questions, we first see a small N400 effect (Kutas & Hillyard, 1980), a negative effect after about 400 milliseconds, which has been related to processing of unexpected words in a sentence. After this negativity, a large positive effect emerges which appears to be sustained until the response. We tentatively interpret this positivity to reflect a cognitive process associated with the response, such as the retrieval of the answer or the planning of production. These results thus show that in a question-answer sequence, speakers appear to start planning their response immediately when they have enough information to do so. Further results in the domain of brain oscillations and localizations of the effects in the brain will also be discussed. These results imply that cognitive processes might have a different timing than interactional processes. In some cases (as in our 'early questions'), the cognitive processes might be ready while interactionally the answer has to be postponed until the speaker finished speaking, possibly freeing up cognitive resources for a better timing of the response, for example. In other cases, cognitive processes might still be ongoing while the speaker has already finished her turn, for example when the question is difficult, calling for other interactional mechanisms such as the use of fillers. Future studies might employ the patterns of brain activation found to determine the presence and timing of cognitive processes within different types of action-sequences