Jean Piaget studied psychology, focusing on the development of thinking and child development. In his studies, he discovered that children between the ages of seven and 11 develop abilities that he termed multiple classification. Multiple classification is the regrouping of objects into a hierarchy of classes and subclasses based on common features.
Multiple classification falls under the concrete operational stage. A child in this stage will realize that he or she can categorize objects into subcategories. For example, in a large category such as dogs, children will learn that dogs are comprised of subclasses such as big dogs, little dogs and medium sized dogs. Those could even be further grouped into color, like brown, white, black and multicolored.
The child can also learn about ascending and descending hierarchies. For example, a child will realize that a rose is a flower and roses have petals, so therefore all flowers have petals. According to Drs. Robert Karplus and Celia Stendler Lavatelli, children can easily sort a deck of cards that have ducks, birds and mammals. Those children that can exhibit this classification will separate the cards into three piles and be able to sort into ascending and descending hierarchies.
Piaget discovered that this stage marked the beginning of a child’s cognitive development. In this stage, children discover they can solve more complex problems and use simple logic. Additionally, children aren’t able to think abstractly at this point. They understand conservation, however. Conservation is when a particular amount of something stays the same, even if it changes shape. Children in the concrete operational stage will also understand reversibility, or things being able to return to their original condition after being changed.
Seriation is “the ability to arrange things in a sensible order,” like arranging a set of straws according to increasing or decreasing length. Piaget’s explanation of seriation also includes children being able to master arbitrary series like the alphabet and numbers. Basically, the child can sort objects according to specific characteristics within a series, like size, color, shape, the alphabet or even numbers.