The main desire of Vygotsky was to design a new way to look at and come up with a solution to educational and social problems of the time. He believed other factors, besides biological instincts, caused humans to act the way they do. He was the first modern psychologist to suggest a way in which culture plays a part in each person's nature. Vygotsky believed the inclusion of sign systems from a child's culture changes behavior and connects early and later forms of individual development. Vygotsky was a strong supporter of the idea that what children learned from other people in their own culture helped them develop. He considers human thought processes to be based on social interactions and language. Three key areas of sociocultural theory are the zone of proximal development, private speech and make-believe play.