Steady Beat Sound Facilitates both Coordinated Group Walking and Inter-Subject Neural Synchrony

Abstract

Group walking is a collective social interaction task as pedestrians are required to determine their own pace of walking on the basis of surrounding others’ states. The steady beat sound is known to be a controllable factor that contributes to relative success/failure of coordinated group walking since the beat improves pedestrian flow in congested situation. According to some reports, inter-personal interaction synchronizes inter-personal brain activity in the prefrontal region, which supports social cognitive processes required for successful inter-individual coordination, such as predicting each other’s state; success/failure of a coordinated task is associated with increase/decrease in inter-subject neural synchrony (INS). Combining these previous findings, we hypothesized that INS during group walking in congested situations would also differ depending on the existence of the steady beat, corresponding to the modulated coordination-related cognitive processes. Subjects’ frontopolar activities were measured using ultra-small near infrared spectroscopy, which can simultaneously measure the brain activities of multiple subjects without constraints on their motions. To exclude the possibility that increased INS may be spuriously induced by the shared stimuli (i.e., steady beat) or by the resultant behavioral synchronization, as control we used stepping on a same spot, which is similar in movement to walking but does not require the subjects to consider others’ states, either with or without the steady beat. In a two by two repeated measures factorial experimental design, the subjects were instructed to walk or keep stepping on a same spot with or without a steady beat sound of 70 beats per minute. As previously reported, the walking flow during group walking with the beat significantly increased compared with that without the beat. Synchronization of stepping between the subjects was also significantly increased by the steady beat sound. For INS, we observed a significant interaction effect between walking/stepping and sound/no-sound, supporting our hypothesis. INS while walking with the beat was higher than that without the beat, whereas the beat induced no significant differences in INS during stepping. Furthermore, the effect of the beat on INS while walking was spatially extended beyond the adjacent pedestrians, reflecting the diffuse nature of the collective coordination in group walking. The increase of INS for walking suggested that the steady beat sound led to more harmonized inter-personal cognitive processes, which resulted in the more coordinated group motion.

Hyperscanning: A Valid Method to Study Neural Inter-brain Underpinnings of Social Interaction

“…As it is the most common method that is used to analyze interbrain synchrony with fNIRS, it is also the most common analysis method within all hyperscanning studies. WTC was used to estimate inter-brain synchrony in paradigms studying action monitoring (Dommer et al, 2012), cooperative and competitive behaviors (Cui et al, 2012;Osaka et al, 2014;Cheng et al, 2015;Liu et al, 2016b;Wang et al, 2019), imitation , verbal communication (Jiang et al, 2012(Jiang et al, , 2015Nozawa et al, 2016), non-verbal communication (Osaka et al, 2015;Hirsch et al, 2017), decision making (Tang et al, 2016;Zhang et al, 2017), coordination Ikeda et al, 2017;Pan et al, 2017) , mother-child problem solving (Nguyen et al, 2019), and teaching/learning behaviors .…”

Brain-to-brain synchronization across two persons predicts mutual prosociality

“…high tolerance of head/body motion), functional near-infrared spectroscopy (fNIRS) technique has been used to examine the dynamic interbrain activities in relatively natural settings. There were enhanced synchronous brain activities among individuals in together key pressing ( Funane et al , 2011 ), active motor imitating ( Holper et al , 2012 ), cooperative singing/humming ( Osaka et al , 2014 , 2015 ) and coordinated group walking ( Ikeda et al , 2017 ). Consistent with the EEG studies, the fNIRS studies found the increased IBS mainly at the frontal area (including pre-motor cortex, left inferior frontal cortex and frontal pole), and further, the detected brain synchronization was correlated with the synchronized performance.…”

Prior physical synchrony enhances rapport and inter-brain synchronization during subsequent educational communication

“…These 6 results suggest that the application of hyperscanning to the evaluation of IBS in the field of educational communication is promising [41][42][43][44][45][46] , especially to probe into the degree of harmonization in social affective and cognitive processes involved in the communication. However, although several studies reported changes in IBS during coordinated physical activities [47][48][49][50] , no study so far has directly addressed the link between the positive effect of prior physical synchrony and IBS during subsequent communication.…”

“…This finding of prior physical synchrony enhancing IBS in the subsequent communication may be regarded as the most significant contribution of the current study. Previous physical coordinationrelated IBS studies observed interpersonal neural coordination during physical interaction[47][48][49][50] . Moreover, there is an fMRI study that probed into individual brain activity changes during and immediately after synchronous/asynchronous beat generation with ostensible partners (actually a computer program)60 .…”