The concept of a linguistic hedge has been successfully formalized in the field of fuzzy set theory. The meaning of linguistic expressions such as "very tall" have been well expressed by using membership functions. Although various methods for measuring the membership functions have been proposed, the change of the meaning in the real world is not treated well. In this paper, we introduce the concept of population type for the perceived data set, and conduct psychological experiments to determine the membership functions for the linguistic expressions, changing the stimulus population type. Then, by using the concept of population type, we propose a technique for adjusting the system's knowledge of linguistic hedges to new perceived data, and discuss the usefulness of the method.
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