Erik Erikson’s theory explains that human development progresses thought a conflict. Life situations give rise to a state of cognitive conflict, because the tall glass cannot both contain more and contain less than the wide glass. The cognitive conflict activates the motivational process, equilibration, which functions to remove that conflict, and in the process generate new schemes which will be on a higher cognitive level. In the case of conservation, through equilibration, the child resolves the conflict by viewing the problem in a whole new way. In contrast to Erikson, Margaret Mahler theory, known as separation-Individuation theory, explains that child development starts with separation from his mother and understanding of a separate identity. The child's mental processes are then reorganized, or restructured to take on board the new flexible thinking capability (Feldman 2006, p. 54). In the aftermath of mental reorganization, enormous potential for a mental growth spurt opens up. The child can now view the world in a new light. For example, the child now has the mental flexibility to view the world from another viewpoint, and therefore no longer suffers the egocentrism characteristic of the preoperational stage. The main similarity between theories is that they view a child development as a continuous and gradual process pushed by ego development and identity recognition. In this case, the motivational force of equilibration, stimulated by cognitive conflict, pushed the child onto a higher and more flexible cognitive level. Both of these theories help social workers to understand child development and causes of social problems (Feldman 2006, p. 231). Also, they allow a social worker to foreshadow psychological changes and introduce intervention programs for children. Development is partly driven by an internal motivation, with the idea that humans are such that they find learning and development to be pleasurable experiences. Behavior plans of intervention will aim to correct and guide behavior of children and help them to overcome social and psychological conflicts. Behavior plans of intervention are the most effective ones as they imply direct intervention of a social worker and allow to achieve fast and good results at the shortest period of time. They are developed for each child and take into account psychological uniqueness of every individual.