Cognitive and moral development in research In the wide field of developmental psychology at infancy at adolescence there is one specific topic which is called 'cognitive development'. This topic was and is researched by many psychologists. One of the most famous developmental psychologists is Jean Piaget with his 'theory of cognitive development'. Jean Piaget's almost 100-year-old ideas are still contemporary and present in nowadays psychological researches. Piaget's theory consists of four phases with different focuses and lengths. Herefrom arises the question of how it is possible to study the cognitive skills of an infant who is not yet able to speak. Also those children, who are already developed the ability to speak, will not be up to evaluate their cognitive skills from an objective point of view. Therefore psychologists were searching for methods to either support the theory of Jean Piaget or to refute his assumptions. Today, psychologists have a wide range of exercises for testing the cognitive skills of an infant. They found out that already children at the age of five months are able to understand simple mathematical exercises. In one exercise the babies were confronted with a situation in which a rabbit was shown. Then a board was positioned in front of the rabbit. The babies could only see the board, not the rabbit. After that another rabbit disappeared behind the board. When the board was removed by the psychologists, only one rabbit was shown to the babies. The babies recognized that something was wrong because they reacted different from when the correct result with two rabbits was presented to them later. The theory of Jean Piaget was not only verified by other psychologists but also extended by another famous psychologist, Lawrence Kohlberg. He disposed the 'theory of moral development'. Today, we have a complete knowledge about human cognitive and moral development, based on the theories of Piaget and Kohlberg. Sources: - Piaget, J. (1928). Theory of Cognitive Development. - Kohlberg, L. (1986). Theory of Moral Development.