The environment that constrains our behavior includes not only objects and events but also other members of our species. When we dance or talk or work together to accomplish a goal, our behaviors are guided by information about others within our social niche. Research in this laboratory strives to apply ecological psychology’s law-based perspective–in particular, exploiting methods from dynamical systems and affordance research–to study how we perceive and act with others. Experiments examine transitions from individual to social behavior, including possible influences on the degree of synchrony between two people who may or may not intend to coordinate.