Sensorimotor substages refer to the different stages of development that infants and young children go through as they learn to use their senses and motor skills to interact with the world around them. These substages, which were first described by child psychologist Jean Piaget, are an important part of the overall sensorimotor stage of development, which occurs from birth to about 2 years of age.
During the first sensorimotor substage, which occurs from birth to about 1 month of age, infants are primarily concerned with exploring the sensations of their own bodies. They will bring their hands to their mouths and faces, and may also kick and wave their arms and legs. At this stage, infants do not yet have a sense of object permanence, meaning that they do not understand that objects continue to exist when they are not in view.
The second sensorimotor substage, which occurs from about 1 to 4 months of age, is characterized by the development of the "grasp reflex," in which infants will automatically grasp objects that are placed in their hands. They will also begin to use their senses to explore their environment, such as by looking at and reaching for objects. During this substage, infants also begin to show signs of stranger anxiety, meaning that they become distressed when around people they do not know.
The third sensorimotor substage, which occurs from about 4 to 8 months of age, is marked by the development of "primary circular reactions," in which infants will repeat actions that produce interesting or pleasing sensations. For example, an infant may shake a rattle to hear the noise it makes, or put a toy in their mouth to feel the texture. At this stage, infants also begin to show signs of separation anxiety, meaning that they become distressed when separated from their primary caregiver.
The fourth sensorimotor substage, which occurs from about 8 to 12 months of age, is characterized by the development of "secondary circular reactions," in which infants will intentionally repeat actions in order to produce a desired outcome. For example, an infant may intentionally drop a toy and then look to an adult to pick it up and give it back to them. At this stage, infants also begin to show signs of object permanence, meaning that they understand that objects continue to exist even when they are not in view.
The fifth and final sensorimotor substage, which occurs from about 12 to 24 months of age, is marked by the development of "tertiary circular reactions," in which infants will vary their actions in order to explore the different possibilities and consequences of their actions. For example, an infant may try different ways of stacking blocks to see which way works best. At this stage, infants also begin to show a greater sense of self-awareness and to engage in more symbolic and imaginative play.
Overall, the sensorimotor substages are an important part of the early development of infants and young children, as they provide the foundation for more complex cognitive and social skills that will be developed in later stages of development. Understanding these substages can help parents and caregivers support the development of their children in a way that is appropriate for their age and abilities.