Children's hypothetical reasoning about complex and dynamic systems

Children's hypothetical reasoning about a complex and dynamic causal system was investigated. Predominantly White, middle‐class 5‐ to 7‐year‐old children from the Greater Toronto Area learned about novel food chains and were asked to consider the effects of removing one species on the others. In Study 1 (N = 72; 36 females, 36 males; 2018), 7‐year‐olds answered questions about both direct and indirect effects with a high degree of accuracy, whereas 5‐year‐olds performed at chance. Six‐year‐olds showed intermediate performance. Using food chains with clearer constraints, Study 2 (N = 72; 35 females, 37 males; 2020–2021) replicated these findings. These results indicate that the ability to think about hypothetical changes to dynamic causal systems develops between 5 and 7 years. Implications for science education are discussed.