Comparative thinking is a very natural form of thought that even a small baby has. The baby distinguishes between his parents and a stranger. People compare and contrast all the time. You compare the quality and price when you buy a kitchen utensil, for example. In order to compare, we first need to sort them. We need to decide the attributes we are sorting them by. For example, to sort our kitchen cabinet, we need to choose the attribute, could be by function, material or by size.
Intuitive behaviour is not a formal process. The ability to compare and contrast using a logical, scientific process requires training and understanding of the process of classification, discrimination, transition and use of the right vocabulary. CLASSIFICATION is the first step where you find attributes (criteria) to compare. DISCRIMINATION is the second step where you distinguish and articulate the differences. From this you draw inferences and conclusions while using TRANSITION or CONTRASTING VOCABULARY like whereas, however, etc.
We use visual thinking tools that enable this kind of thinking. Some of the tools used are the semantic feature analysis chart or matrix diagram, double bubble diagram and Venn diagram. This is an essential tool that can be used across subjects. I have extensively used this in Math, Science, Social Studies and English. Here are a few examples.
Step 1: Classification
Step 2: Discrimination