Students must categorize the examples or non-examples (those which do not show essential characteristics of the concept rule)
by explaining why they do or do not fit the concept rule being discussed.
The teacher presents the concept rule of: a square is an object with four congruent sides.
The teacher defines congruent as equal, then he/she shows the students examples of squares, possibly tables or objects in the classroom which have the desired qualities as well as
The students, with guidance from the teacher, identify the following characteristics that must be present (CRITICAL ATTRIBUTES) for the object to be a square: a) the object has four sides
and b) the object's four sidesre equal (i.e. all have sides which are 10 inches long, or 5 inches, etc).
The teacher then elicits the non-critical attributes of a square. (i.e. shape is non-critical or non-essential as long as it meets other characteristics,
meaning it could be 2 or 3 dimensional; size is also non-essential; weight is non-essential to the concept rule; etc.)
The teacher shows more examples of a square, but mixes them in with rectangles (non-examples). Students must distinguish the difference and verbalize it.