Y. Saeki, a cognitive psychologist, claims that a feeling of "indeed" is important for deeper understanding and proposes several models for the sake of true understanding. In this article, the credibility of his claim and the validity of his models were examined. For this purpose, the following three mental models proposed by Saeki were analyzed: (1) a model for understanding the area of a parallelogram (2) a model for understanding the direction of spool movement (3) a model for understanding pulley movement. An analysis from the viewpoints of internal consistency and experimental verification showed that these models are not only full of contradictions but also are not supported by any experimental evidence and that a feeling of "indeed" does not guarantee true understanding and sometimes may even accompany false understanding. Based on the results of this analysis, it was concluded that Saeki's claim is not valid and a new interpretation of this feeling was presented