According to the stages of cognitive development suggested by Piaget, the earliest period is called the Sensorimotor stage. Stages of Cognitive Development suggested by Jean Piaget:Sensorimotor stage: Birth to 2 years- During this earliest stage of cognitive development, infants and toddlers acquire knowledge through sensory experiences and manipulating objects. A child's entire experience at the earliest period of this stage occurs through basic reflexes, senses, and motor responses.Preoperational stage: Ages 2 to 7- The foundations of language development may have been laid during the previous stage, but the emergence of language is one of the major hallmarks of the preoperational stage of development.Concrete operational stage: Ages 7 to 11- While children are still very concrete and literal in their thinking at this point in development, they become much more adept at using logic.Formal operational stage: Ages 12 and up The final stage of Piaget's theory involves an increase in logic, the ability to use deductive reasoning, and an understanding of abstract ideas.Additional Information Piaget's theory differs in important ways from those of Lev Vygotsky, another influential figure in the field of child development. Vygotsky acknowledged the roles that curiosity and active involvement play in learning but placed greater emphasis on society and culture.Hence, According to the stages of cognitive development suggested by Piaget, the earliest period is called the Sensorimotor stage.