Three-year-old children understand the false beliefs of their partner in collaborative decision making.

Classic false-belief tasks may be confusing because children converse with someone who knows that a situation has changed about a third person who does not know this. Two studies used a collaborative false-belief task in which US- and UK-based 3-year-olds (N = 84, 48 girls, data collection: 2023) and a partner had to jointly decide in which box a toy was hidden. Children informed their partner and provided reasons about the location of the toy more when their partner had a false belief than when they had a true belief. We discuss the hypothesis that collaborative decision making pushes children to understand how their partner's perspective relates to their own and, when they differ, to assess how each corresponds to reality.