Lifespan Development. Tara L. Kuther

smelling it, and tasting it. Piaget (1952) believed that infants are not capable of mental representation—thinking about an object using mental pictures. They also lack the ability to remember and think about objects and events when they are not present. Instead, in order to think about an object, an infant must experience it through both the visual and tactile senses. The sensorimotor period of reasoning, as Piaget conceived of it, progresses through six substages in which cognition develops from reflexes to intentional action to symbolic representation.

      Substage 1: Reflexes (Birth to 1 Month)

      In the first substage, newborns use their reflexes, such as the sucking and palmar grasp reflexes, to react to stimuli. During the first month of life, infants use these reflexes to learn about their world, through the process of assimilation; they apply their sucking schema to assimilate information and learn about their environment. At about 1 month of age, newborns begin to accommodate, or modify, their sucking behaviors to specific objects, sucking differently in response to a bottle versus a pacifier. For example, they may modify their sucking schema when they encounter a pacifier, perhaps sucking less vigorously and without swallowing. During the first month of life, newborns strengthen and modify their original reflexive schemas to explore the world around them.

      Substage 2: Primary Circular Reactions (1 to 4 Months)

      During the second substage, infants begin to make accidental discoveries. Early cognitive growth in the sensorimotor period comes through engaging in circular reactions, the repetition of an action and its response. Infants learn to repeat pleasurable or interesting events that originally occurred by chance. Between 1 and 4 months, infants engage in behaviors called primary circular reactions, which consist of repeating actions involving parts of the body that produce pleasurable or interesting results. A primary circular reaction begins by chance, as the infant produces a pleasurable sensation and learns to repeat the behavior to make the event happen again and experience the pleasurable effect again. For example, an infant flails her arms and accidentally puts her hand in her mouth. She is surprised at the outcome (her hand in her mouth) and tries to make it happen again. Therefore, the infant repeats the behavior to experience and explore her body.

      In the first substage (birth to 1 month), newborns use their reflexes to respond to stimuli. They strengthen and modify their reflexive schemas to explore the world around them.

      iStock/Stefano Oppo

      In the second substage (1 to 4 months), infants discover that they can control their bodies and repeat the behavior to experience and explore their bodies.

      iStock/W6

      Substage 3: Secondary Circular Reactions (4 to 8 Months)

      During the third sensorimotor substage, as infants’ awareness extends further, they engage in secondary circular reactions, repetitions of actions that trigger responses in the external environment. Now the patterns of repetition are oriented toward making interesting events occur in the infant’s environment. For example, the infant shakes a rattle to hear its noise or kicks his legs to move a mobile hanging over the crib. Secondary circular reactions indicate that infants’ attention has expanded to include the environment outside their bodies and that they are beginning to understand that their actions cause results in the external world. In this way, infants discover new ways of interacting with their environments to continue experiencing sensations and events that they find pleasing.

      During the third sensorimotor substage (4 to 8 months), infants’ awareness extends to include objects. They repeat actions to view and experience their effects on objects.

      iStock/FamVeld

      Substage 4: Coordination of Secondary Circular Reactions (8 to 12 Months)

      Unlike primary and secondary circular reactions, behaviors that are discovered by accident, the coordination of secondary circular reactions substage represents true means–end behavior and signifies the beginning of intentional behavior. During this substage, infants purposefully coordinate two secondary circular reactions and apply them in new situations to achieve a goal. For example, Piaget described how his son, Laurent, combined the two activities of knocking a barrier out of his way and grasping an object. When Piaget put a pillow in front of a matchbox that Laurent desired, the boy pushed the pillow aside and grabbed the box. In this way, Laurent integrated two secondary circular reactions to achieve a goal. Now planning and goal-directed behavior have emerged.

      One of the most important advances during the coordination of secondary circular reactions stage is object permanence, the understanding that objects continue to exist outside of sensory awareness (e.g., when they are no longer visible). According to Piaget, infants younger than 8 months of age do not yet have object permanenc—out of sight is literally out of mind. An infant loses interest and stops reaching for or looking at a small toy after it is covered by a cloth. Not until 8 to 12 months, during the coordination of secondary circular reactions stage, will an infant search for hidden objects, thus displaying object permanence. This development is an important cognitive advance because it signifies a capacity for mental representation, or internal thought. The ability to think about an object internally is an important step toward learning language because language uses symbols: Sounds symbolize and stand for objects (e.g., infants must understand that the sound “ball” represents an object, a ball).

      During the fourth substage (8 to 12 months) infants demonstrate object permanence, the understanding that objects exist outside of sensory awareness.

      Doug Goodman / Science Source

      During the fifth substage (12 to 18 months), infants begin to experiment with new behaviors to see the results.

      iStock/MartinPrescott

      Stage 5: Tertiary Circular Reactions (12 to 18 Months)

      During the fifth substage, infants begin to experiment with new behaviors to see the results. Piaget described infants as “little scientists” during this period because they move from intentional behavior to systematic exploration. In what Piaget referred to as tertiary circular reactions, infants now engage in mini-experiments: active, purposeful, trial-and-error exploration to search for new discoveries. They vary their actions to see how the changes affect the outcomes. For example, many infants begin to experiment with gravity by dropping objects to the floor while sitting in a high chair. First an infant throws a ball and watches it bounce. Next a piece of paper floats slowly down. Then mommy’s keys clatter to the floor. And so on. This purposeful exploration is how infants search for new discoveries and learn about the world. When presented with a problem, babies in the tertiary circular reactions substage engage in trial-and-error analyses, trying out behaviors until they find the best one to attain their goal. Figure 5.2 illustrates primary, secondary, and tertiary reactions.

      Substage 6: Mental Representation (18 to 24 Months)

      The sixth sensorimotor substage marks a transition between the sensorimotor and preoperational reasoning stages. Between 18 and 24 months of