Previously, research on wishful thinking has found that desires bias older children's and adults' predictions during probabilistic reasoning tasks. In this article, we explore wishful thinking in children aged 3- to 10-years-old. Do young children learn to be wishful thinkers? Or do they begin with a wishful thinking bias that is gradually overturned during development? Across five experiments, we compare low- and middle-income United States and Peruvian 3- to 10-year-old children (N = 682). Children were asked to make predictions during games of chance. Across experiments, preschool-aged children from all backgrounds consistently displayed a strong wishful thinking bias. However, the bias declined with age.

Research on wishful thinking suggests that desires bias adult’s probability judgments. Previous research has yet toexplore if this extends to young children. In Experiment 1, 260 4- and 6-year-olds in the U.S. and Peru played a card game,where selecting a desirable card was unlikely. In Experiment 2, 200 4- to 6-year-old children were shown a bag of plasticeggs; a few contained desirable prizes. Children were asked to make predictions about what card / egg would be randomlyselected. Answers were compared to control conditions in which probability was comparable, but children had no reason todesire a specific outcome. In control conditions, children tended to state that the majority card/ egg would be selected. In theexperimental conditions, children were more likely to state that the desirable (and improbable) card/ egg would be selected.Results suggest that a desire bias extends to children as young as 4.