Lev Vygotsky was a Soviet psychologist known for his sociocultural theory of cognitive development, which emphasized how social interaction and culture impact cognitive development. He is renowned for concepts like the zone of proximal development, which refers to the difference between what a learner can do independently and what they can do with guidance and collaboration, and the more knowledgeable other, someone with more understanding to help the learner. Vygotsky founded the Vygotsky Circle to research cultural-historical psychology focused on how social learning precedes development.