人际同步是个体之间在时间上相互协同的运动,是一种非常普遍的社会互动 行为。从两个人保持步伐一致到成千上万的观众一起鼓掌,人们能够在各种规模 的群体内达成同步。对于建立更为复杂和灵活的社会交互,这种与他人保持同步 的能力是基础。人际同步能够让人与人之间的关系更为紧密亲近,也能够促进亲 社会行为的发生。探索人际同步的内在认知与神经过程对于理解人际同步的形成 和维持十分重要。先前研究主要关注的是人际同步的个体认知过程。然而,当两 个人或多个人在同步时,他们会形成一个完整的交互系统。这一交互系统会涌现 出单个个体所不具有的整体属性,这是仅从个体层面无法刻画的。因此,本论文 认为从整体视角研究人际同步的内在过程是十分必要的,并提出了相应的方法。 人际同步的整体视角研究方法包括两部分。1)从整体视角定义人际同步的 认知过程。基于线性误差校正模型,本论文提出人际同步的整体认知过程,包括 整体内在时钟、整体运动执行和整体误差校正,并定义了相应的量化指标。在人 际同步中,整体内在时钟负责规划和预测同步行为发生的时刻,整体运动执行负 责将预测的同步行为付诸实现。由于这两个过程不可避免的存在噪声,会给同步 过程带来误差,因此,还需要整体误差校正对同步误差进行纠正。由线性误差校 正模型可推导出同步表现是由这三个整体认知过程的综合效应决定的。2)从整 体视角定义人际同步的神经过程。在人际同步过程中,本论文采用近红外多脑成 像技术进行双脑或多脑的同时观测,并将脑间同步性或群体脑网络作为两人或多 人同步的整体神经过程,用以表征交互成员在同步中进行信息传递的过程。在提 出这一方法后,本论文用双人同步按键实验对该方法进行了有效性和可重复性验 证,并将该方法在多人同步中进行了推广尝试。 首先,本论文以固定节奏的双人同步按键为例,对整体视角研究方法进行了 有效性验证。该实验设置了双向同步和单向同步条件,在进行同步按键的同时用 近红外多脑成像技术记录双人脑活动。在理论上,同步表现由整体误差校正、整 体内在时钟变异和整体运动变异的综合效应决定。实验结果验证了这一结论,具体表现为 1)实际同步表现在双向条件下显著优于单向条件,整体认知过程的综 合效应所预测的同步表现与实际表现近似,并且也有一致的条件间差异;2)在 每个实验条件内,不同双人组的同步表现与整体认知过程综合效应所预测的同步 表现成显著正相关。进一步的,单个整体认知过程对同步表现有不同的作用。具 体来说 1)整体误差校正是双人同步表现的主要影响因素。交互整体对误差校正 的越充分,同步表现越好。2)整体内在时钟与理解他人有关,表现为整体内在 时钟变异与共情能力和右侧前额叶的脑间同步性存在显著负相关(后两者都与对 他人的理解有关),即理解他人的能力越强,整体内在时钟变异越小。3)整体运 动执行的功能是运动输出,对同步表现的影响较小。在双人同步中,整体神经过 程表现为脑间同步性。右侧前额叶的脑间同步性在单向条件下显著高于双向条件, 这可能与单向条件下听觉反馈信息不充分,需要更多地对他人进行揣测有关。 其次,本论文对人际同步的整体视角研究方法进行了可重复性验证。在上述 实验完成后,同样的被试在一周后重复了相同的实验任务。同步表现与整体认知 过程的综合效应在第二轮实验中得到了重复验证。具体表现为同步表现依然在双 向条件下优于单向条件,并且该条件间差异可以由整体认知过程的综合效应解释。 同步表现在条件内的被试间差异也同样与整体认知过程的综合效应成显著正相 关。此外,该实验发现单个整体认知过程的效应出现了变化。与理解他人有关的 过程在第一次实验中是整体内在时钟,在第二次实验中变为整体误差校正。这提 示整体认知过程会受到人际熟悉度的影响。在彼此陌生时,人们需要对他人的特 质进行揣测,即重点关注内在时钟的稳定性;而在了解对方行为模式之后,关注 点转变为对交互状态的关注,即当前同步误差的校正情况。整体神经过程也受到 了人际熟悉度的影响。熟悉后,右侧前额叶的脑间同步性在单向和双向条件间的 差异消失。这可能是因为熟悉后单向条件下理解他人的难度降低,右侧前额叶的 脑间同步性也降低,从而与双向条件下的差异减小。 最后,本论文尝试将人际同步的整体视角研究方法推广到多人同步中。以九 人敲鼓为例,类比双人同步的双向与单向条件,实验设置了协同敲鼓条件和跟随 节拍器敲鼓条件。首先,协同敲鼓条件的同步表现优于跟随节拍器敲鼓,该结果 与双人同步时双向条件的同步表现优于单向条件类似。跟随节拍器敲鼓还出现了 后期同步表现变差的现象,协同条件则没有。双人同步时,主要影响同步表现的是整体误差校正,但在九人同步时,整体误差校正在两个条件间没有显著差异, 都足以达到维持同步所需的程度。主要影响因素转变为整体内在时钟变异及其在 交互成员之间的一致性,交互成员的整体内在时钟变异越小,成员之间的变异程 度越小,同步表现越好。这表明当群体人数增加时,误差来源增多,有效减少误 差来源是提高同步表现的关键。群体脑网络结果表明,与心理理论有关的内侧前 额叶和颞顶联合皮层两个脑区,在群体脑同步性(即群体脑网络的平均连接强度)、 群体脑网络的全局效率和局部效率三个属性上,均在协同敲鼓条件下高于跟随节 拍器敲鼓,并且在同步早期高于中晚期。当同步出现波动时,内侧前额叶的群体 脑同步性和群体脑网络全局效率在重新建立同步阶段要高于失去同步阶段。这些 结果一致地表明了当群体成员之间的交互需求增加时,群体脑网络的同步性和效 率就会增高,当这种交互需求降低时,群体脑网络的同步性和效率就会降低。

Interpersonal synchronization is a temporal coordinated movement among individuals that is prevalent in our social life. From synchronized gait between two persons to synchronized hands clapping among thousands of people, human can establish synchronization within different sizes of groups. This ability to coordinate with others is fundamental to establish more complex and flexible social interactions. Interpersonal synchronization can strengthens social bonding and facilitate prosocial behavior. To explore underlying cognitive and neural processes is crucial to understand establishment and maintenance of interpersonal synchronization. Previous studies mainly focus on individual cognitive processes of interpersonal synchronization. However, when two or more people synchronize with each other, they form a holistic interaction system. The holistic system may emerge new characteristics which beyond individual level. Thus, this thesis proposed holistic view and method of interpersonal synchronization. Holistic view and method of interpersonal synchronization includes two part:1) holistic cognitive processes. Based on linear error correction model, the thesis proposed holistic cognitive processes, which include holistic error correction, holistic internal timekeeper and holistic motor execution, and defined corresponding quantitative measurements. During interpersonal synchronization, holistic internal timekeeper is responsible for arrange and predict the time point of behavior. Holistic motor execution implement the predicted behavior. Inevitable noises of these two processes lead to synchronization errors, thus holistic error correction is essential to correct errors and maintain synchronization. During interpersonal synchronization, this thesis used fNIRS-hyperscanning technology to observe two or more brains simultaneously, and used inter-brain coupling or multi-brain network as holistic neural processes of two or more people’s synchronization. Then, the thesis validate the holistic view and method using two-person synchronization, and expand it to multi-person synchronization. Firstly, the thesis validate holistic processes on two-person synchronization with stable tempo. In this experiment, bidirectional and unidirectional condition were set. According to linear error correction model, synchronization performance is decided by integrated effect of holistic error correction, holistic internal timekeeper and holistic motor execution. The result confirmed this theoretic conclusion in two ways.1) Real performance is significantly better in bidirectional condition than unidirectional condition. The performance predicted by integrated effect of holistic cognitive processes is similar to real performance and has same between-condition difference. 2) within each condition, performance of different dyads is significantly correlated with integrated effect of holistic cognitive processes. Each holistic cognitive process has different effect on performance.1) Holistic error correction is the main factor influencing performance. More efficient the error correction, more synchronous the performance. 2) Holistic internal timekeeper is related to understanding others. The variation of holistic internal timekeeper is significantly correlated with empathy/ inter- brain coupling of right PFC. Better understanding of others, less variation of holistic internal timekeeper. 3) Holistic motor execution is output and has little influence on performance. Inter-brain coupling is the holistic neural process of dyad’s synchronization. Inter-brain coupling of right PFC is significantly higher in unidirectional condition than in bidirectional condition. This may relate to the more requirement of mentalizing due to inefficient auditory feedback in unidirectional condition. Secondly, based on the previous experiment, the thesis validate repeatability of holistic view and method. All participants came back one week later and performed the same task. They were strangers to each other in the first experiment and familiarized partners’ synchronized behavioral pattern in the second experiment. Between-condition difference of performance and integrated effect of holistic cognitive and neural processes were confirmed in the second experiment. What familiarity influenced is the effect of single holistic cognitive process. What related to understanding others is V holistic internal timekeeper in the first study and is holistic error correction in the second one. This indicate that familiarity make people’s focus shift from others’ trait to interaction state. Familiarity also influence holistic neural process. The difference of right PFC’s inter-brain coupling between conditions disappear after familiarization. This may due to the decreased requirement of understanding others along with decreased inter-brain coupling in the unidirectional condition. Finally, the thesis attempt to expand holistic cognitive and neural processes from two-person synchronization to multi-person synchronization. Similar to bidirectional and unidirectional condition in dyad synchronization, there are self-coordinated condition and metronome-instructed condition in a nine-person synchronization experiment. Synchronization performance is significant better in the self-coordinated condition than in the metronome-instructed condition, and performance deteriorate in the late period of the instructed condition. The main influence factor of performance is holistic error correction in the dyad’s synchronization, but is holistic internal timekeeper in multi-person synchronization. In nine-person synchronization, holistic error corrections are almost same in two conditions, both are sufficient to maintain synchronization. However, noise of holistic internal timekeeper is significant when group size become larger. The multi-brain networks of mPFC and TPJ relating to mentalizing show higher network synchronization and efficiency when interaction requirement are higher, such as self-coordinated condition, early period of synchronization and reestablishment of synchronization after chaos.