The periodization of human development is not a fictional or self-centered scientific problem. Its value is determined by the quality reproduction of the human personality. For this reason, this problem is key in all major human sciences such as psychology. Psychology examines and reflects the different periods of mental and personal development of the individual, defines scientific criteria for characterization of the psychic abilities and qualities of each period, determines the methods for evaluation and diagnosis of realized opportunities during a given period.
Psychology also analyzes the interrelation between the factors of mental development: heredity, the natural environment, the social environment, the education and the activity of the individual. Solving the problem of age periodization provides a practical solution to extremely important social issues. Mental development occurs in childhood at a different rate - different periods occur in the same duration in the psyche. Every mental quality is different at each and every moment for each individual person and either he or she does not. Mental qualities have a hierarchical structure whose components are also in a hierarchy. Mental development is of periods of interrupted nature - mental qualities are built over relatively long periods of time but occur in relatively short periods of time. There are many hypotheses about the stages of mental development. It is based on the assumption that a new psychic quality emerges at a certain moment of development. These moments divide childhood into periods and are the boundaries between them.
Border moments are called "crises" in development, because in a short time the psyche is rapidly changing, noticeable. There have been a number of age-based periodications by various researchers working on this issue, namely: 1. Jean Piaje - built on the fact that new qualities of thinking have emerged; 2. Z. Froud - on the appearance of new qualities of emotions / the change of the area of the body, which causes sexual pleasure / - oral, anal, phallic, etc. periods; 3. Eriksson - the emergence of psychic qualities governing joint behavior with other people / autonomy, intimacy, hard work, etc. /. This is the most popular modern theory of age periodization, developed by the prominent representative of the "Psychology of the Self". His perceptions of personality, its development, individual creativity and its relation to social factors have a sustainable impact on psychology.
These periodizations are contradictory, and there are reasonable doubts about each. Their use is therefore causing difficulties. The boundaries in the different periods are the same. Exactly defined moments in the development of the psyche mean the beginning and the end of the age period. Such moments are: - the end of the first year after birth; - 18 months after birth - 3 years old; - enrollment in school; - the beginning of sexual maturation. They represent the moment of changing one period to another.