Lev Vygotsky (1896-1934) was a Russian psychologist most known for his sociocultural theories on cognition. Vygotsky developed the Social Development Theory which proposed that the social environment was integral to the development of higher cognition and that learning preceded development. Social and cultural influences are highly influential on a individual's cognitive development and are essential in the formation and development of it.
Vygotsky believed that the elementary mental functions (attention, perception, memory, and sensation) would be shaped and formed by the social environment to eventually develop into higher mental functions. Vygotsky also developed the concept of the Zone of Proximal Development which is the range of tasks that are too difficult for a person to learn alone, but can be learned with guidance from someone with experience in the task.
Vygotsky died of tuberculosis at the age of 38.