“…The study of internal parameters might focus on the peripheral nervous system with measures such as skin conductance ( Kragness and Cirelli, this issue ) or heart rate ( Thorson et al , this issue ) or on brain changes with neuroimaging measures. Interestingly, the latter is pursued most frequently not with functional magnetic resonance imaging, which many consider the gold standard of neuroimaging, but with other less popular techniques including the electroencephalography ( Heggli et al , this issue ; Schirmer et al , this issue ; Zamm et al , this issue ), magnetoencephalography ( Levy et al , 2017 ) and functional near-infrared spectroscopy ( Dieffenbach et al , this issue ; Kruppa et al , this issue ; Nguyen et al , this issue ; Pinti et al , this issue ). This choice nicely reflects the need to capture the fast temporal dynamics characterizing interactional synchrony and/or the need for fairly unconstrained face-to-face interactions (but see Misaki et al , this issue ).…”