The Brain Behind the Response: Insights Into Turn-taking in Conversation From Neuroimaging

Figures & data

Box 1. Overview of Neuroimaging Methods.

In functional magnetic resonance imaging (fMRI), participants lie in a large machine and perform a certain task while their brain is “scanned.” Participants’ blood flow to different brain areas is measured (indirectly), which is related to the activation level of these areas while participants perform a task. However, the measure is relatively slow, since the blood flow lags a few seconds behind the actual activation of the area. In contrast, the methods of electroencephalography (EEG) and magnetoencephalography (MEG) show very precisely when certain brain activity occurs. However, the exact location of the effects is more difficult to pinpoint with these methods (albeit a bit better with MEG than EEG). Two commonly used methods for analyzing EEG/MEG data are the following. In event-related potentials (ERPs), EEG signals are (as mentioned in the text) averaged over a large number of trials, leading to a number of peaks and troughs that can be compared between conditions. For example, the so-called N400 component (a negative wave that is largest around 400 ms after the start of a word; Kutas & Hillyard, 1980) has been found to index the expectedness of words (see Figure 3 for an example). A second method of analysis concerns the time frequency of oscillatory activity in the brain (here referred to as “frequency analysis”). In this case, one analyzes the way a stimulus modulates the power (amplitude) of ongoing background oscillatory rhythms (“brain waves”) at different frequencies in the brains of individuals at a particular moment in time. This is usually presented visually like a spectrogram, representing the power at different frequencies and time points (see Figure 4 for an example). For more information on these methods, see, for example, handbooks edited by Cacioppo, Tassinary, and Berntson (2007) and by Luck and Kappenman (2011).

Figure 1. Illustration of the early planning and the late planning model for the timing of cognitive turn-taking processes.

Figure 2. Sample stimuli and main results for Gisladottir et al. (2015).

Figure 3. Results from Bögels et al. (2015) for yes and no responses after a 300-ms gap (left) and a 1,000-ms gap (right).

Figure 4. Setup (panel A) and results (panel B) for the ERP (top) and time-frequency domain (bottom) from Bögels, Magyari, and Levinson (2015).

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Cacioppo, J. T., Tassinary, L. G., & Berntson, G. (2007). Handbook of psychophysiology. Cambridge, England: Cambridge University Press.

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Luck, S. J., & Kappenman, E. S. (2011). The Oxford handbook of event-related potential components. Oxford, England: Oxford University Press.

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