A Computational Model of Change in Politeness with the Addition of Word Endings

Abstract

Many polite expressions can be synthesized using simple expressions in Japanese. It is expected that such syntheses are dominated by psychological mechanisms in politeness. This study reveals one such mechanism by using a computational model for politeness in Japanese to describe changes in politeness through the addition of word endings. In this model, two stochastic features are assumed: (1) For each expression, a situation in which the expression would be used can be represented by a probability distribution of the politeness value in a psychological space, and (2) For each word ending e, a probability distribution exists in a one-dimensional psychometrical space of politeness, where the distribution represents the ideal distribution of the most suitable (or ideal) expression to which the word ending e would be added. The change in politeness that arise from the addition of word endings is calculated by the difference between these probability distributions. The information theory is utilized in this calculation. A linear relationship is expected to exist between the change in politeness that arise from the addition of word endings to expressions and the politeness of the original expressions. Psychological experiments were performed to verify the validity of the model. The degree of politeness of expressions was evaluated using Thurstone’s scaling. Experimental results show the expected linearity to be true which qualitatively verifies the validity of the model. The results are also discussed in terms of linguistic intuition.