The age category is one month to four months. Primary circular reactions follow the baby's reflexive actions, such as crying and squirming. The child develops repetitive patterns centered on the body. Examples of body center patterns are toe sucking, thumb sucking, or sucking on an object after looking at it. The child will intentionally repeat the pattern because he will find it satisfying. Piaget's four fundamental principles can be applied to the subphase of the primary circular reaction. Since a baby has the sucking reflex, whenever an object touches his lips, he will suck on the object. Piaget would have said that it has a "sucking pattern". The baby will develop again