The Development and Legacy of Jean Piaget's Cognitive Development Research Jean Piaget conducted numerous experiments involving children , ultimately introducing the idea of ​​four stages in children's cognitive development. His research has been criticized over the years, but his work paved the way for psychologists who came after him. Psychologist Jean Piaget made astonishing contributions to the developmental field of psychology. At a very young age, Jean Piaget showed interest and potential for scientific research, but he had no institutional training in psychology. His interest in knowledge, which encompasses a large part of his work, comes from his godfather, Samuel Cornut. One of his first jobs in psychology was recording children. Piaget's research helped him discover that children structure their knowledge differently than adults. He believed that there were four stages in a child's intellectual development (Cohen, 2011, p. 27). The first sensory and motor stage described how children learn about their environment through the senses and motor action. This stage also includes the concept of object permanence which generally lasts until eight months of age. Babies who have not overcome object permeance do not search for an object once it is out of sight and will focus their attention on something new. The preoperative stage is the second and occurs in children aged two to seven years. At this stage, they do not need to rely on physical contact to acquire knowledge and can reflect on an event after it has occurred (Cohen, 2011, p. 161). However, they cannot decenter themselves, meaning they only focus their attention on one object at a time. Cohen (2011) gives the example of children believing that taller people must be older than shorter people (p. 161). The third stage is the concrete operational phase, which lasts seven to eleven years. At this stage, they have the concept of decantation. Unlike the preoperative phase, children can assimilate several details of an object at once. The final stage is the formal operational phase, which begins around age twelve. At this stage, children begin to think about possible, abstract, hypothetical ideas (Cohen, 2011, p..