The participants repeated the task eight times; the first two rounds were called pretraining sessions and the last two were posttraining sessions. The four sessions in between were the cooperative training sessions, in which one persona randomly chosen leadermade a sequence of large finger movements, and the other participant was instructed to follow the movements. In the posttraining sessions, finger-movement correlation between the two participants was significantly higher compared to that in the pretraining sessions. In addition, socially and sensorimotor-related brain areas were more synchronized between the brains, but not within the brain, in the posttraining sessions. According to the researchers, this experiment, while simple, is novel in that it allows two participants to interact subconsciously while the amount of movement that could potentially disrupt measurement of the neural signal is minimized.
"The most striking outcome of our study is that not only the body-body synchrony but also the brain-brain synchrony between the two participants increased after a short period of social interaction," says Yun. "This may open new vistas to study the brain-brain interface. It appears that when a cooperative relationship exists, two brains form a loose dynamic system."
The team says this information may be potentially useful for romantic or business partner selection.
"Because we can quantify implicit social bonding between two people using our experimental paradigm, we may be able to suggest a more socially compatible partnership in order to maximize matchmaking success rates, by preexamining body synchrony and its increase during a short cooperative session" explains Yun.
As part of the study, the team also surveyed the subjects to rank certain social personality traits, whic
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