Final answer:
The theory referred to is Jean Piaget's theory of cognitive development, which explains how children learn and develop through stages, starting with the sensorimotor stage from birth to age 2, where they learn through sensory perceptions and motor behavior.
Step-by-step explanation:
The theory that describes development as proceeding from reflex activity to representation and sensory motor learning is Jean Piaget's theory of cognitive development. Piaget proposed that children's development unfolds in four stages, with the sensorimotor stage being the first one.
From birth through age 2, a child in the sensorimotor stage learns about the world around them primarily through their sensory perceptions and motor behavior. Developmental milestones during this stage include the progression from rudimentary reflexes to the development of object permanence and the ability to engage with the environment in increasingly complex ways.
Motor development in infants begins with reflexive reactions such as sucking and rooting and then moves towards more advanced motor functioning like sitting, crawling, and eventually walking. Piaget's theory asserts that cognitive development is key to learning how to interact with one's surroundings effectively, and motor skills are developed as infants explore and make sense of their world.