A child in the concrete operations stage can reason differently than can a child in the sensorimotor stage. For example, if shown two identical balls of clay, one of which has been rolled into a rope, an older child (one in the concrete operational period) might decide that the ball and the rope both have the same amount of clay. What kinds of reasoning do you think the older child might use to draw that conclusion?

The child would be using the reasoning that allows him to understand reversibility operation and reciprocity operation.

Explanation:

Through the reversibility operation the child can understand that some things after being changed can return to their original state. In the case shown in the question above, the child was able that once the clay ball was rolled on top of the rope, he could redo his clay concentration and reaching the same amount of clay as the rope. We can also state that the child understands the concept of reciprocity operation, since she understands that the changes that the ball undergoes are a consequence of the amount of clay that the ball has.