Three-year-old children's reasoning about possibilities.

Recent studies in cognitive development suggest that preschoolers may not be able to represent alternative possibilities, and therefore may lack modal concepts such as possible, impossible, and necessary (Leahy & Carey, 2020). We present two experiments adapted from previous probability studies but have a similar logical structure as those used in the previous modal reasoning tasks (Leahy, 2023; Leahy, Huemer, Steele, Alderete, & Carey, 2022; Mody & Carey, 2016). Three-year-old children have to choose between a gumball machine that must produce the desired gumball color and a gumball machine that merely might produce the desired gumball color. Results provide preliminary evidence that three-year-old children can represent multiple incompatible possibilities, and therefore have modal concepts. Implications for the study of modal cognition, and how possibility and probability may be related are discussed.

Minimal representations of possibility at age 3.

Young children do not always consider alternative possibilities when planning. Suppose a prize is hidden in a single occluded container and another prize is hidden in an occluded pair. If given a chance to choose one container and receive its contents, choosing the singleton maximizes expected reward because each member of the pair might be empty. Yet, 3-y-olds choose a member of the pair almost half the time. Why don't they maximize expected reward? Three studies provide evidence that 3-y-olds do not deploy possibility concepts like MIGHT, which would let them represent that each container in the pair might and might not contain a prize. Rather, they build an overly specific model of the situation that correctly specifies that the singleton holds a prize while inappropriately specifying which member of the pair holds a prize and which is empty. So, when asked to choose a container, they see two equally good options. This predicts approximately 50% choice of the singleton, observed in studies 1 and 3. But when asked to throw away a container so that they can receive the remaining contents (study 2), they mostly throw away a member of the pair. The full pattern of data is expected if children construct overly specific models. We discuss whether 3-year-olds lack possibility concepts or whether performance demands prevent deployment of them in our tasks.