Heuristics for scientific experimentation: a developmental study

Scientific discovery involves search in a space of hypotheses and a space of experiments. We describe an investigation of developmental differences in the search constraint heuristics used in scientific reasoning. Sixty-four subjects (technically trained college students, community college students with little technical training, 6th graders, and 3rd graders) were taught how to use a programmable robot. Then they were presented with a new operation, provided with a hypothesis about how it might work, and asked to conduct experiments to discover how the new operation really did work. The suggested hypothesis was always incorrect, as subjects could discover if they wrote informative experiments, and it was either plausible or implausible. The rule for how the unknown operation actually worked was either very similar or very dissimilar to the given hypothesis. Children focused primarily on plausible hypotheses, conducted a limited set of experiments, designed experiments that were difficult to interpret, and were unable to induce implausible (but correct) hypotheses from data. Adults were much better than children in discovering implausible rules. The performance deficits we found were not simply the result of children's inadequate encoding or mnemonic skills. Instead, the adults appear to use domain-general skills that go beyond the logic of confirmation and disconfirmation and deal with the coordination of search in two spaces: a space of hypotheses and a space of experiments.