Classification skill is central to the development of concrete operations. It is the ability to group objects according to common attributes. It allows children to put their world in order and simplify it. This period appears to be more organized and orderly based on what is immediately present.
Class inclusion: It is considered as a concrete operational thought. It is the child’s knowledge that a super ordinate class is always larger than any of its subordinate classes. The child is able to reason simultaneously about part and whole. For example two subordinate categories of two super ordinate category- seven pictures of dogs and three pictures of cats. The children are asked whether there are more dogs or more animals. Even though preschoolers are able to count number of dogs and cats but correct responses on class inclusion problems are not found reliable until late childhood.
Multiple classifications: ability to make comparisons between whole class of objects and subsets within the class. During late childhood children’s ability to consider several dimensions at once will be developed.
For ex. Children are shown an array of objects that differ in two or more ways and are asked the missing object that best fits in the array. Children must consider the two dimensions of the objects simultaneously. To solve the problem in the above figure the child must select an object based on two dimensions like colour and shape.
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