Cognitive development in infancy and toddlerhood forms the foundation for later intellectual, emotional, and social competencies, and Jean Piaget’s theoretical framework offers a detailed explanation of how infants begin to understand and organize their world. During this period, children progress through the sensorimotor stage, which spans from birth to about two years. Piaget described this stage as a period when cognition is rooted in sensory experiences and motor actions rather than in mental representations. The major characteristics of cognitive development during infancy and toddlerhood can be understood by examining the progression through the six substages of the sensorimotor period, along with the broader principles of adaptation, assimilation, accommodation, object permanence, and the emergence of symbolic thought. In the earliest substage, known as reflexive activity, infants rely on innate reflexes such as sucking, grasping, and blinking. These reflexes serve not merely as automatic responses but as the foundation for later cognitive advancements. Through repeated interaction with the environment, infants begin to modify these reflexes, demonstrating the early forms of learning and adaptation. For example, the sucking reflex evolves as infants differentiate between objects such as a nipple, finger, or pacifier. Piaget saw this modification as the earliest sign that infants are capable of constructing knowledge by interacting with their environment rather than by passively absorbing information. The second substage involves primary circular reactions, emerging around one to four months. Here, infants discover pleasurable actions performed on their own bodies and repeat them. These reactions illustrate the beginning of intentionality, although still centered on the infant’s own physical experiences. A baby who accidentally brings their hand to their mouth may repeat the action because it produces comfort, demonstrating early forms of learning through repetition. This stage marks a significant step in cognitive differentiation as infants start refining motor patterns and coordinating simple sensory experiences. As infants reach four to eight months, they enter the phase of secondary circular reactions. Unlike primary circular reactions, where actions focus on the infant’s own body, secondary circular reactions involve external objects and events. Infants now show greater interest in the environment and actively explore ways to reproduce interesting outcomes. For instance, an infant may repeatedly shake a rattle to hear its sound. Piaget emphasized that this developmental shift reflects cognitive growth because infants begin to understand that their actions can produce effects in the outside world. At this stage, they begin to form rudimentary cause-and-effect relationships, although these understandings remain