Fig. 3

Ladderized trees manipulated to construct assessment questions. Sample questions developed using selected tetrapods. Dashed and dotted lines, along with numbered nodes illustrate the result using the node counting strategy to determine the relationships between the focal taxon and the two potential answers. Measurement bars along the top illustrate proximity between the focal taxon and each of the two potential answers. Each question was controlled to pair an answer using most recent common ancestor with one alternative strategy (i.e., proximity, similarity, or node counting), all three in unison (multiple) or no alternative strategies (none). a Initial ladderized tree as it might typically be presented in textbooks. b Similarity distracter: the focal taxon looks more similar to the distracter than to the correct answer while proximity of the terminal nodes and internal nodes separating the taxa are equal. c Proximity distracter: the proximity of the distracter taxon is closer than the MRCA taxon to the focal taxon; the similarity and number of internal nodes separating the taxa from the focal taxon are equal. d Node counting distracter: there are fewer internal nodes separating the focal taxon from the distracter than to the most closely related taxon; similarity of taxa and proximity of the taxa at the terminal nodes is equal. e None: proximity of the terminal nodes, similarity of the taxa and internal nodes separating the taxa are equal. f Multiple distracters: distracter looks similar, is closer, and has fewer intervening nodes from the focal taxon than does the most closely related taxon