The aspect of human mental development has always been a mystery for scientific society and even ordinary people. Centuries of studying the evolution of the human mental system still left many questions needing answers. The main aspects of human behavior could be more understandable. Scientists try to explain human intellectual evolution from the point of view of different theories which deal with children’s and adult’s psychology. One theory tries to add to another, but they usually repeat each other’s statements in different words and do not generate a new vision of a given situation. This idea is rather critical, but it comes from analyzing a certain amount of theories and articles by scientists with expertise in this area. This research aims to compare two theories of cognitive development, Piaget’s and Vygotsky’s, and to find the advantages and disadvantages of these approaches in forming social relations and cognitive development of social interaction. The analysis of the above ideas will represent a model of human behavior in different age and development conditions. Thus, we would see the influence of different factors on personality formation. This work aims to compare the two theories in action and their influence and discuss the results of this research. Children’s behavior would be the main subject of this research, as adult behavior evolves from children’s behavior. Thus, to see the development of human behavior, the survey would start from when this behavior only begins to form. Nowadays, human development is a very important topic for discussion in the scientific community and even in every family, as the process of children’s development plays an important role in their future life and the formation of social relations. In order to understand how a person will behave in certain situations in the future, one should know what influences his character and behavior now. Our behavior and character start forming in early childhood. In other words, we are the product of our early development. That means that to be a successful, smart, and kind person; one should start to form and develop these features from early childhood. The main theories of human development and social integration prove this idea. Both cognitive theories of Piaget and Vygotsky try to explain and show the factors that directly influence human growth, development, and social activity. The first theory to discuss is Piaget’s cognitive development theory. This theory discusses the cognitive development of children of different ages. Piaget divided the process of development into separate stages. According to his theory, during their growth, children pass four long-term stages of cognitive development. All of them have differences in logical thinking, ways of behavior, and perception of reality. At the sensorimotor stage (from birth to approximately 2 years old), the child uses senses and movements to explore the world and express himself. The next statement shows the most significant features of children during the pre-operational stage (from 2 to 7 years of age). Children are less egocentric at this age; they rarely confuse fantasy with reality and can change their thinking. Then, during the concrete operations stage (from 7 to 11 years of age), the way of understanding the world is transformed into a more organized way of thinking, social activity increases, and children are more likely to spend more time interacting with other children. Finally, during formal operations (from age 11 onwards), thinking becomes complicated and similar to adults. This theory divided the entire academic society into two groups. The first group supports the idea that quality changes are gradual, and a certain period is needed for them to transfer. Others tend to believe that changes in the cognitive sphere occur continuously and do not depend on stages. Some researches focus on the role of social and cultural aspects in the development of children. The next theory to discuss is Vygotsky’s cognitive development theory. Scientists believe children’s understanding of social relations influences their thinking. This information could be collected through technical devices or the process of communication. He pointed out the importance of language as the main tool for collecting this knowledge. Children can get this kind of information from mostly adult people through language. The scientist insists on the teacher’s importance, speaking about the person who has more knowledge and is ready to share it. He called this category the more knowledgeable other (MKO). This category can include parents, teachers, and even computers. In his theory, he described the zone of proximal development, and this idea served as a key point of his theory. Vygotsky used to include two levels for this zone of proximal development. Level 1 is a present level of development, and it illustrates a child’s ability to perform certain actions without anybody’s help. Level 2 is a potential level of development, and it shows the potential ability of a child to perform actions with the help of others. Vygotsky describes the period that takes place between these two levels as the zone of proximal development. Scientists developed the idea that children can gain more knowledge by interacting with others, including teachers, adults, and parents. However, this information must correspond with the child’s level of development. Information that is too difficult for the child to understand should be transferred to the further development period. If a child develops, he gets more knowledge and is ready to continue studying more difficult concepts. Scaffolding is another important point in this theory. The process of sharing knowledge by adults depends on their level of development. Thus, they provide a child with the information collected by them before. For example, a child who is trying to learn how to walk might have both of his/her hands held upward for the first time. The mother should support the first experience in walking, and she might hold both of his/her hands to help him/her in this process. After some practice, she might hold only one hand, and this help will be sufficient. This progress in the process of using somebody’s help is called scaffolding. This concept can be compared with the process of building. It is a kind of support for new constructions, and it becomes less essential when the building is complete. Vygotsky showed his perspective on the process of learning. Piaget’s theory should have highlighted the influence of cultural knowledge more fully. Therefore, it is obvious that both theories try to present their view on the aspects that form children’s behavior. Combining these two theories is a good idea because sharing knowledge is as important as cognitive development in different stages and integration with the social environment. One can choose the idea he/she likes more, but the academic society still has not found an answer to a range of questions that can support any of these ideas and continue comparing and evaluating them against each other. ? References: 1. Eddy, S 2010, Theories of Cognitive Development: Lev Vygotsky, Viewed 1 April 2013. 2. Kail, R, Cavanaugh, J 2013, Human Development: a life-span view, 6th edition, Wadsworth/ Cengage Learning, Belmont, CA.