Proceedings of the Annual Meeting of the Cognitive Science Society

We hypothesized that college biology students difficulty interpreting relationships depicted in evolutionary trees (clado-grams) at least partly reflects their responding based on Gestalt grouping principles. Students from non-majors introduc-tory, majors introductory, and upper-level biology classes (N = 310) evaluated two pairs of cladograms after classroominstruction on evolutionary trees. The cladograms in each pair depicted the same evolutionary relationships among threetarget taxa but grouping of those taxa differed due to Gestalt principles. Students were asked which cladogram best repre-sents the specified relationships among the target taxa or whether both cladograms are equally good (the correct answer).As predicted, for all three biology groups, students responses most often were consistent with the Gestalt principles ofgrouping rather than with the pattern of evolutionary relationships (M = 1.28 out of 2; t(309) = 13.55, p ¡ .001). Clearly,biology instruction needs to address the potentially interfering role of Gestalt grouping.