The purpose of this study was to examine the influence of transitivity cue on children's performance to class-inclusion tasks. Based on the score of transitivity test, forty-seven five-year-old children were selected and the practice trials were administered to them. All of them could the not understand the class-inclusion relationship in the pre-test. They were randomly devided into two conditions: the first one was to be given transitivity cue without reinforcement (NR condition) while in the second one verbal reinforcement (R condition) was added in practice trials. The followings are the main results at the post-test of class-inclusion.(a) Children in R condition obtained a higher percentages of correct responses than children in a NR condition.(b) In R condition, the high level group in transitivity development performed more correct responses than the low level group.(c) There was no facilitation effect in R a condition.