Two- and three-year-olds coordinate decisions in dyads and triads.

Even young toddlers coordinate actions with a partner. But coordinating choices or decisions is more challenging, particularly in multi-party groups. In this pre-registered study (data collected from Fall 2023 to Spring 2025), 2- and 3-year-olds (n = 100, 50% female, 26% underrepresented minority) needed to select "keys" that matched in color to open a box. Children coordinated with one another in same-aged dyads or triads. In dyads, children of both ages were mostly successful, whereas 3-year-olds were much more successful than 2-year-olds in triads. This was especially true in a generalization trial in which only one of ten 2-year-old triads was successful, while all other groups were successful. Success at both ages was predicted by rates of cooperative communication about their choice of key. These results demonstrate that even 2-year-olds can coordinate choices with a single partner, but doing so in groups tends to emerge at around age three, when children begin to develop more advanced ways of thinking about and working with others.