The purpose of this study is to measure the development of language comprehension of infants, and to construct a multi-stratified adaptive questionnaire by refining the scale presented by Takei and Ogino. The scale presented by Takei and Ogino has so many items that it is laborious to answer all the questions. By employing the adaptive testing method, it was expected to keep the reliability of the questionnaire with considerably fewer items for each mother to answer. Based on this expectation, we made a questionnaire with 6 strata, and administered it to over the 160 mothers who have infants between 3 and 24 months old. The result shows that the reliability of the questionnaire can be kept high with about 1/3 items compared with the original one
