Psychology is a broad discipline that includes many subfields and one of these subfields is “educational psychology”. Educational psychology seeks to understand the development and learning processes of individuals (especially students). Developmental psychology has clarified many concepts related to human development, such as development, growth, maturation, readiness, critical period. In addition, the factors affecting development have also been examined in this field, and the common effects of environment and heredity on human development have been tried to be explained. In this context, it is emphasized that appropriate environmental conditions are necessary for the potential powers inherited through heredity to emerge. Important principles related to development are also defined.

When explaining development, developmental periods and the tasks specific to these periods should also be taken into account. The process of development is divided into specific stages, from fertilization to death, and at each stage there are certain skills and behaviors that the individual must fulfill. These tasks are called “developmental tasks”. Developmental periods have been analyzed by different researchers by dividing them into various stages. Theorists such as Freud, Erikson and Piaget have made important contributions in this field. In each period, the characteristics specific to that period and the problems encountered were defined. In this framework, the developmental stages proposed by Havighurst and divided into six phases are explained.

Theories are of great importance in psychology and this is also true for developmental research. Developmental theories explain events and phenomena, aim to reach generally valid norms and enable the determination of universal principles. In addition, theories offer the possibility of predicting future events. Researchers studying development have addressed this process within the framework of various theories. The main theories of development are summarized.