Abstract: Humans have an inherent ability to perceive biological motion (BM) in their surroundings and align with its rhythm, even when it is depicted through a simplified arrangement of light points. Point-light BM, although simplified, encompasses global configuration and local motion trajectories, which are crucial for perception. Prior research has advanced our understanding of BM processing, but few studies have thoroughly investigated the respective roles of global configuration and local motion in beat synchronization with BM. This study aimed to investigate the mechanisms underlying the interaction between global configuration and local motion information during beat synchronization with BM.
This study comprised three experiments involving 30, 27, and 33 Chinese participants in experiments 1, 2, and 3, respectively. All the experiments employed a beat synchronization paradigm, in which participants were required to concurrently engage in beat synchronization and change detection tasks. The materials utilized in experiment 1 included standard, scrambled, and inverted scrambled BM. Experiment 2 comprised scrambled, inverted scrambled, and scrambled uniform BM. Experiment 3 encompassed standard, unscrambled uniform, scrambled, and scrambled uniform BM. The stability of beat synchronization was the primary dependent variable across all experiments.
Experiment 1 demonstrated that beat synchronization stability under the standard BM condition was considerably higher than that observed in the scrambled and inverted scrambled BM conditions. This finding highlights the critical role of global configuration information in the synchronization process. In Experiment 2, under the condition of disrupted global configuration, a comparison of the three local motion states showed that disrupting either the biological nature of motion direction or the biological nature of speed variation resulted in no significant difference in synchronization stability compared to preserving local biological motion. The lack of global configuration information may restrict the influence of local motion on the stabilization of synchronization. Experiment 3 revealed an interaction: when the global configuration was intact, disrupting the biological nature of local speed variation significantly reduced synchronization stability; however, when the global configuration was disrupted, synchronization performance showed no difference between preserving and disrupting the biological nature of local motion. This finding suggests that global configuration is essential for the functioning of local motion information.
This study demonstrated that beat synchronization with BM is influenced by global configuration and local motion, and global configuration exerts a dominant influence. The findings can be analyzed using Bayesian theory: when the global configuration of BM is preserved, human-like information activates preexisting brain templates, providing prior knowledge, and local motion presents likelihood information that corresponds with these predictions. This condition ensures efficient sensorimotor timing, which is evidenced by increased stability in beat synchronization. Conversely, when the global configuration is disrupted, strong priors cannot be established, and the brain becomes insensitive to the biological nature of local motion; consequently, local motion has no significant effect on synchronization performance. The findings align with Bayesian theory and offer a novel perspective on the mechanisms underlying BM timing process.

Key words: biological motion, beat synchronization, global configuration, local motion