"Dr. Tess is doing a study to determine how 9-year-olds think. Based on theory, they believe that the 9-year-olds should be able to reason logically about concrete situations situations that are real, tangible, and visible. Dr. Tess's belief is based on:" the information-processing perspective. Jean Piaget's theory of cognitive development. Lev Vygotsky's theory of cognitive development. Erik Erikson's theory of psychosocial development