Abstract: A modified Piagetian's class inclusion task and a simplifiedclassification task were presented to prechoolers. The results indicated: 1. The ability of solving class inclusion problem was facilitatedby three factors(1)endowing general class with the common attributionsof perception, (2)highlighting the common attributions in instruction,(3) comparing sub-class with general-class by counting performance. 2. Several stages were involved in solving the class inclusionproblem: First, children around the age of 4 could only compare theindividual attributions of a subclass with those of another one. Theydid not know that generality exists in individuality. Secondly, childrenbetween 5-6 could compare sub-class with general class bearing theattributions of perception, and the whole through the senses perceived.Finally children around the age of 7 and above could solve classinclusion problem in the abstract and recognize the logical relationshipbetween the part and the whole. 3. The hierarchical structure of class was shown in the 3 to4-year-olds when familiar stimuli were manipulated in a simplified task ofclassification.

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