Can young children grasp causality in scenarios involving two causal variables?

Human ability to learn causality is important because it allows us to imagine alternative possibilities and design new interventions to achieve desired outcomes. When two causal variables affect different dimensions of an outcome, it is necessary to understand the effects of each causal variable to achieve a desired outcome. The current research examined whether young children can learn the effects of each causal variable. In two studies, Japanese children aged 4–6 years (Study 1, N = 99, 51 girls) and 5–6 years (Study 2, N = 60, 31 girls) saw a sequence of events in which causal variable A made differences in shape, and causal variable B made differences in size to produce an outcome. The results showed that when asked to create a novel shape (size), those aged 5–6 years chose to intervene on a causal variable that previously created a shape (size) difference. These findings suggest that children aged 5–6 years can recognize distinct effects of each causal variable and use these to determine an intervention that would create a novel effect state.