Abstract
Developmental patterns of human's various functions are not the same. Therefore, it is necessary to investigate characters of the developmental stages based on developed change in various functions. College student subjects were asked to evaluate what degree 1 year old, 3 years old, 5 years old, 10 years old, 20 years old, 50 years old and 80 years old people would be able to do 20 evaluation items well by themselves. The pattern of developmental change in various functions was different. Methods of the definition and the explanation of the developmental stage by applying the fuzzy set theory are discussed.
