Lev Semenovich Vygotsky (Russian: Лев Семёнович Выготский or Выготский, born Lev Simyonovich Vygodsky) was a Soviet developmental psychologist and the founder of cultural-historical psychology.
Vygotsky believed that learning is the support which leads to development. He opposed both Piaget’s belief that development led to learning and Skinner’s belief that learning is a change in behavior due to the environment. Instead, he advocated for assessment of the zone of proximal development, which is “the distance between the actual developmental level as determined by independent problem solving and the level of potential development as determined through problem solving under adult guidance or in collaboration with more capable peers” (Vygotsky, 1978, p. 38). Regardless of ability, it’s necessary to determine a baseline, or the level of independent problem solving, and to assess potential development.