Co-Principal Investigator: Kefyn Catley

Purpose: In biology, a type of hierarchical diagram called a cladogram is used to depict evolutionary histories among species or groups of species. These diagrams are the most important tool that contemporary scientists use to reason about evolutionary relationships. Such understanding has been termed "tree thinking." Recently, a number of researchers have argued that this approach must be incorporated into the biology curriculum if any progress toward meaningful science literacy in this domain is to be made. This project has three primary goals. The first goal is to identify and understand the cognitive and perceptual factors that influence high school and college students' ability to understand and reason from cladograms. This information is critical for developing (a) effective curricula for teaching tree thinking, and (b) assessments that will allow students to demonstrate their competence in this domain (therefore, their understanding of macroevolution). The second goal is to create novel curricula, where none currently exist, to teach tree thinking at the undergraduate and high school levels. The final goal is to provide an initial implementation and assessment of the curricula in biology classes.

Project Activities: In this project, the research team will conduct a set of seven experiments using within-subject designs to identify and understand the cognitive and perceptual factors that influence high school and college students' ability to understand and reason from evolutionary trees. Researchers will then use the results from the experiments to develop curriculum materials to teach tree thinking at the undergraduate and high school levels. They will test the implemented curricula in a pre-test/post-test design using measures developed in previous work.

Products: The products of this project include a curriculum unit to teach tree thinking at the undergraduate and high school levels, and published reports regarding the cognitive and perceptual factors that influence high school and college students' ability to understand and reason from cladograms.

Structured Abstract

Setting: The cognitive experiments involving college and high school students will be conducted primarily in Tennessee and rural western North Carolina. Eye-tracking studies will take place in California.

Population: Study participants include 250–300 college and 60–100 10th-grade biology students. The students in the study will be predominantly white, affluent, and female.

Intervention: Researchers will create novel curricula where none currently exist to teach tree thinking at the undergraduate and high school levels. Components of the intervention will be based on the results of the cognitive experiments and may include examples of phylogenetics in action, initial field work, activities to distinguish synapomorphies from synplesiomorphies, and questions-of-the-week.

Research Design and Methods: During Year 1 of the study, researchers will conduct seven laboratory experiments with college students using standard experimental psychology methods. Researchers will manipulate cognitive and perceptual factors hypothesized to affect cladogram understanding and reasoning, including types of graphic representations, the arrangement in which information is presented (e.g., from left to right), characteristics of the graphics associated with students' misconceptions, and factors such as domain familiarity. To monitor how students process information, eye movements will be recorded as participants scan cladograms for a later recognition task. Experiments are repeated in a modified format with 10th-grade high school biology students in order to calibrate the difficulty of these tasks and to verify that the cognitive and perceptual factors that affect cladogram comprehension and reasoning in college students are also relevant for understanding the performance of 10th graders. Responses from participants will include constructing cladograms, retrieving information from cladograms, and making inferences based on information provided in cladograms. During Years 2 and 3, the team will use the results from the laboratory experiments to design an intervention to support learning of macroevolution concepts at the college level (Year 2) and then, in a modified version, at the high school level (Year 3). Researchers will test the implemented curricula in a pre-test/post-test design using measures developed in previous work.

Control Condition: The experimental manipulations (e.g., the location of the taxon on the ladder, or the type of cladogram) are each implemented in a within-subjects design. Subjects will be equally divided between those with weaker versus stronger backgrounds in biology.

Key Measures: To assess the impact of the cladogram curricula, students will complete a pre-test prior to instruction and a post-test after instruction. The items for these tests will be selected from among the tasks used in the cognitive studies designed to identify and understand the cognitive and perceptual factors that influence high school and college students' ability to understand and reason from cladograms. Dependent measures will include accuracy, types of errors made, and types of evidence cited in support of one's answer.

Data Analytic Strategy: Data analytic methods will include relevant parametric (e.g., analysis of variance) and non-parametric (e.g., chi-square) statistical analyses.

Products and Publications

Book chapter

Catley, K.M., Novick, L.R., and Funk, D.J. (2012). The Promise and Challenges of Introducing Tree Thinking Into Evolution Education. In K. Rosengren, E.M. Evans, S. Brem, and G. Sinatra (Eds.), Evolution Challenges: Integrating Research and Practice in Teaching and Learning About Evolution (pp. 93). New York: Oxford University Press.

Journal article, monograph, or newsletter

Catley, K.M., Phillips, B.C., and Novick, L.R. (2013). Snakes and Eels and Dogs! Oh, my! Evaluating High School Students' Tree-Thinking Skills: An Entry Point to Understanding Evolution. Research in Science Education, 43(6): 2327–2348.

Novick, L.R., and Catley, K.M. (2012). Assessing Students' Understanding of Macroevolution: Concerns Regarding the Validity of the MUM. International Journal of Science Education, 34(17): 2679–2703.

Novick, L.R., and Catley, K.M. (2014). When Relationships Depicted Diagrammatically Conflict with Prior Knowledge: An Investigation of Students' Interpretations of Evolutionary Trees. Science Education, 98(2): 269–304.

Novick, L.R., Catley, K.M., and Funk, D.J. (2010). Characters are Key: The Effect of Synapomorphies on Cladogram Comprehension. Evolution: Education and Outreach, 3(4): 539–547.

Novick, L.R., Catley, K.M., and Funk, D.J. (2011). Inference is Bliss: Using Evolutionary Relationship to Guide Categorical Inferences. Cognitive Science, 35(4): 712–743.

Novick, L.R., Schreiber, E.G., and Catley, K.M. (2014). Deconstructing Evolution Education: The Relationship Between Micro?and Macroevolution. Journal of Research in Science Teaching, 51(6): 759–788.

Novick, L.R., Shade, C.K., and Catley, K.M. (2011). Linear Versus Branching Depictions of Evolutionary History: Implications for Diagram Design. Topics in Cognitive Science, 3: 536–559.

Novick, L.R., Stull, A.T., and Catley, K.M. (2012). Reading Phylogenetic Trees: The Effects of Tree Orientation and Text Processing on Comprehension. BioScience, 62(8): 757–764.

Phillips, B.C., Novick, L.R., Catley, K.M., and Funk, D.J. (2012). Teaching Tree Thinking to College Students: It's not as Easy as you Think. Evolution: Education and Outreach, 5(4): 595–602.