A Study On The Development Of Sets Perceiving Of Children With Moderate Mental Retardation In Low Grades

Children's sets perceiving had very important meanings to the learning of other mathematics concepts and skills, including number sense, enumeration and arithmetic of adding or subtracting. Compared with normal children in the same age, children with moderate mental retardation faced more difficulty in mathematics understanding and learning, such as enumeration, addition and subtraction. The ability and development of sets perceiving of children with moderate mental retardation in low grades aroused the attention from researcher.Five experiments were used to explore the ability and development of sets perceiving of children with moderate mental retardation. 41 children with moderate mental retardation from grade 1-4 were tested with material objects and picture cards. In this research, the ability of set perceiving included recognizing sets of limited objects, distinguishing between one and many, classifying, understanding the inclusion relation between sets, adding between two sets, operating one-to-one correspondence, understanding set equivalence, counting elements in a set and comparing sets.The results suggested that children with moderate mental retardation in low grades already had the abilities of recognizing sets of limited objects, distinguishing between one and many, adding between two sets and counting elements in a set. These four abilities were stable from grade 1 to grade 4. In addition, the abilities of classifying and operating one-to-one correspondence grew gradually from grade 1 to grade 4. But most children did not compare sets by counting. And they could not understand the inclusion relation between sets and set equivalence even in grade 4.These results indicated that children with moderate mental retardation in low grades had attained stage 3 of sets perceiving. In this stage, they could perceive the elements in the set. But the deficiency of understanding the inclusion relation between sets and set equivalence showed their weakness in the development of number sense concepts, which would influence their further mathematical learning.