The purpose of this study was to examine the existence of the cognitive system which exclude irrelevant feature (i, e. relative size and color) as a criteria for recognition of membership of a specific category effectively in interpreting the meaning of “dog” and “animal”. The subjects were children aged five to six years. In Experiment 1, when the experimenter gave a novel label to two target dogs which were different in size and color, subjects interpreted the label as referring to dogs which were different in size or color from the target dogs. In Experiment 2, when the experimenter gave a novel label to target a dog and a cat which were different in size and color from each other, subjects interpreted the label as referring to dogs and cats which were different in size and color from the target dog and cat. The findings suggested that subjects excluded the relative size and color as a criteria of recognition of membership of a category in interpreting “dog” and “animal”, and the above mentioned cognitive system does exist.