Multistable coordination dynamics exists at many levels, from multifunctional neural circuits in vertebrates and invertebrates to large-scale neural circuitry in humans. Moreover, multistability spans (at least) the domains of action and perception, and has been found to place constraints upon, even dictating the nature of, intentional change and the skill-learning process. This paper reviews some of the key evidence for multistability in the aforementioned areas, and illustrates how it has been measured, modelled and theoretically understood. It then suggests how multistability—when combined with essential aspects of coordination dynamics such as instability, transitions and (especially) metastability—provides a platform for understanding coupling and the creative dynamics of complex goal-directed systems, including the brain and the brain–behaviour relation.

Many social interactions rely upon mutual information exchange: one member of a pair changes in response to the other while at the same time producing actions that alter the behavior of the other. However, little is known about how such social processes are integrated in the brain. Here, we used a specially designed dual-electroencephalogram system and the conceptual framework of coordination dynamics to identify neural signatures of effective, real-time coordination between people and its breakdown or absence. High-resolution spectral analysis of electrical brain activity before and during visually mediated social coordination revealed a marked depression in occipital alpha and rolandic mu rhythms during social interaction that was independent of whether behavior was coordinated or not. In contrast, a pair of oscillatory components (phi ₁ and phi ₂ ) located above right centro-parietal cortex distinguished effective from ineffective coordination: increase of phi ₁ favored independent behavior and increase of phi ₂ favored coordinated behavior. The topography of the phi complex is consistent with neuroanatomical sources within the human mirror neuron system. A plausible mechanism is that the phi complex reflects the influence of the other on a person's ongoing behavior, with phi ₁ expressing the inhibition of the human mirror neuron system and phi ₂ its enhancement.

Significance: The human dynamic clamp (HDC) is proposed as a general paradigm for studies of elementary forms of social behavior in complex biological systems. HDC enables parametric control of real-time bidirectional interaction between humans and empirically grounded theoretical models of coordination dynamics. It thus provides necessary experimental access for laboratory investigations, while preserving the reciprocity and open boundary conditions inherent in daily life social interactions. As proof of concept, different implementations are illustrated, ranging from coordination of rhythmic and discrete movements to adaptive and directed behaviors. The HDC may be a powerful tool for blending theory and experiment at different levels of description, from neuronal populations to cognition and social behavior.