What We Know
Research indicates that the identification of similarities and differences is
a basic component of human thought and that the concept of similarity is
important to different forms of cognition, including memory and
problem-solving (Marzano et al, 2001a; Gentner & Markman, 1997; Sylwester,
Marzano, Pickering and Pollack (2001a) recommend that teachers both present
students with explicit guidance in identifying similarities and differences
and have students identify similarities and differences independently. They
cite four cognitive processes that are effective for generating similarities
and differences: comparing, classifying, creating metaphors and creating
analogies. Instruction of each process should begin with a
teacher-directed model that uses familiar content to teach students the steps
involved. Marzano et al suggest that teachers also use direct instruction in
comparing and contrasting an object or idea whenever a specified set of
similarities and differences is desired. When more diverse conclusions are
sought, the student-directed approach to identifying similarities and
differences should be used. Graphic organizers, particularly for comparisons
and classifications, and guidance should be provided throughout the process.
The use of teacher modeling of cognitive processes until students become
proficient is also supported by Welch (1997). Rich discussion should still
accompany the teacher-directed activity. Discussion and discourse has been
shown to stimulate higher levels of reasoning and metacognition (Mason, 1994).
Using graphic organizers and symbolic stimuli to represent similarities and
differences has been shown to improve students' understanding of content as
well as their ability to recognize and generate similarities and differences
(Cole and McLeod, 1999; Marzano et al, 2000a). In one study, students at all
ability levels who were trained in using graphic organizers when comprehending
texts with a compare-and-contrast structure were found to be able to transfer
the training to real-world tasks (Balajthy and Weisberg, 1988). Another study
involving adolescents with learning disabilities and low-achievement indicated
that explicit strategies for raising the quality of compare-contrast essays
led to improvements in clarity of writing, and appropriateness and
organization of ideas (Wong et al, 1997).
Comparison is the process of identifying similarities and differences
between or among things or ideas.
Classification is the process of grouping things that are alike into
categories based on their characteristics.
Metaphor is a pattern shared by two objects or topics that appear to be
Analogy is a relationship between pairs of objects or concepts.