Results of studies on communication discrepancy and persuasion effect have been quite confusing. In a series of studies conducted by the writer, observations were made that, under experimental conditions, the so-called "boomerang effect," and therefore, little opinion change, occurred at low discrepancy levels, while greater opinion change occurred at higher discrepancy levels. Since it is very difficult to interpret these findings applying the cognitive dissonance theory, the social judgment theory and the psychological reactance theory, the writer postulated the Yin and Yang Theory of Cognition (Sakaki 1984c, 1994). All matters and events occurring in this world are comprised of two opposite, but complementary, components, as brightness to darkness and inside to outside. They exist separately but are dependent upon its counterpart. In human cognition and opinion, a positive opinion has as its counterpart the negative opinion which remains suppressed and latent. As shown in the saying, "The shadow is deep under the strong light," a negative opinion is suppressed behind a strong positive opinion. Stronger the tendency to suppress the negative opinion the stronger the tendency for it to submerge. Such observation suggests a positive correlation between communication discrepancy and opinion change in persuasive communication taking a strict position. On the other hand, in that taking a mild position, the Yin and Yang theory predicts a relationship which can be described as a sigmoid curve. This study was planned to demonstrate the validity of the prediction and this prediction was supported by an experiment with 883 subjects.