Lev S. Vygotsky propounded the cognitive development theory. He explained that experienced adults help children with innate basic abilities to acquire more complex and higher order cognitive abilities. To describe and evaluate this ability, he proposed the concept of ZPD. Based on Vygotsky's thinking, an institutional process was developed in which the amount and nature of cooperation is adjusted in the course of interaction according to the learning needs of the more knowledgeable partner child. According to Vygotsky, psychological tools (devices) and symbols facilitate the thinking process and provide direction for it.