The Importance of Similarities and Differences

Robert Marzano, Debra Pickering, and Jane Pollock, in their book Classroom Instruction that Works (2001), give strong evidence for the effect that the individual classroom teacher has on student achievement. In this researched-based book, they describe 9 instructional strategies that affect student achievement. The strategy that they consider “the core of all learning” is identifying similarities and differences.
According to Marzano et al. (pp. 15-16), teachers enhance “students’ understanding of and ability to use knowledge” when they
• present students with explicit guidance in identifying similarities and differences
• ask students to independently identify similarities and differences
• represent similarities and differences in graphic or symbolic form

While the most recognizable similarities and differences organizer is the Venn diagram, using other lesser-used activities will often yield fresher insights. Besides comparing and contrasting, the following three are processes that require students to think at higher levels:

Classifying—this process asks students to note specific qualities or characteristics. A semantic features analysis chart or a comparison matrix that lists categories or characteristics would use this process.
Creating metaphors—similar to creating analogies, this process asks students to identify a general or basic pattern in a specific topic and then find another topic that appears to be quite different but that has the same general pattern. An example that Marzano’s group uses is comparing the function and structure of the cell to Star Trek’s Enterprise (the nucleus would be like the bridge).
Creating analogies—this process asks students to identify the relationship between pairs of concepts. Analogies are the most complex of the similarities and differences formats as they deal with the “relationships between relationships” (p. 26). Remember the old SAT analogy questions? (Newton is to force and motion as Bernouli is to air pressure.)

With these three levels of similarities/differences, modeling examples for the students before they work on finding their own analogies, metaphors, etc. will reap better results.