Scientific reasoning in a real-world context: the effect of prior belief and outcome on children's hypothesis-testing strategies.

The impact of event outcome and prior belief on scientific reasoning was investigated within a real-world oral health context. Participants (N= 144; ranging from 3 to 11 years) were given hypothesis-testing tasks and asked to explain their answers. Participants were presented with information that was either consistent or inconsistent with their own beliefs. Each task consisted of scenarios in which the outcome was either good or bad oral health. When the information was belief consistent and the outcome was good, or when the information was belief inconsistent and the outcome was bad, children were more likely to choose scientifically appropriate tests of the stated hypothesis (i.e. manipulate only one variable). Evidence-based explanations were associated with scientifically appropriate choices in the good-outcome, belief-inconsistent scenario and the belief-consistent, bad-outcome scenario. Participants' performance on these tasks is explained by considering the plausibility of causal variables. A control of variables strategy was used to test hypotheses in cases in which the evidence was consistent with participants' beliefs and knowledge of causal mechanisms. In contrast, when the evidence was inconsistent with participants' beliefs, children chose to manipulate behaviours likely to lead to a positive health outcome. These findings demonstrate that context and prior knowledge interact to play an important role in children's scientific reasoning.