Provide incentive to understand the nature of development in different periods and how can it help solve and understand the problems that can occur, as appropriate, the individual's age.
The motivation to understand the nature of development in the various periods it is and how it contributes to understand and fix the problem. As appropriate for each age
Incentives in order to understand the characteristics of the development period that is and will be the help in the editing and understand the problem. The suitability of each age.