Hamsters and Parrots and Snakes Oh My

Abstract

Laura R. Novick reports the results of three experiments investigating students’ inferences about living things. In contrast to previous research on categorical inferences, the present research adopts a perspective from evolutionary biology. In all experiments, subjects were told about two (hypothetical) enzymes that help to regulate cell function in two different taxa (e.g., X in the garter snake and Y in the badger). Then they were asked whether a third taxon (e.g., the robin) uses the same enzyme as Taxon 1 or Taxon 2. In Experiments 1 and 2, which involved college students with varying backgrounds in biology, there were two types of critical triads of taxa: (a) amphibians, reptiles, and mammals (reptiles are evolutionarily more closely related to mammals than to amphibians) and (b) plants, fungi, and animals (fungi are evolutionarily more closely related to animals than to plants). In Experiment 3, which involved 10th graders, a third type of critical triad was added: (c) mammals, birds, and canonical reptiles (snakes and crocodilians; birds are reptiles also). In all experiments, some subjects were given a cladogram (a hierarchical branching diagram) depicting the correct evolutionary relationships among the three taxa prior to answering each inference question; other subjects answered the questions based solely on their prior knowledge. Providing cladogram information had different effects depending on the type of triad and the biology background of the subjects. The results illuminate students’ alternative conceptions regarding common taxa as well as their willingness to override this “knowledge” when appropriate evolutionary evidence is provided.