Many of the difficulties that Japanese learners have with English are not due to problems with the language itself but are more the result of cultural differences. Aspects such as age, sex, relationship and relative status heavily influence communication between any two people in Japan. The Japanese generally have an aversion to assertiveness and seek to avoid embarrassment to themselves and their interlocutor. There is a respect for abstraction which is alien to many plain-speaking Westerners. All of this can cause Japanese learners to struggle to find the best way to express themselves and result in the production of English that native speakers may find excessively vague or tentative.
David Watt, in his book ,”The Phonology and Semology of Intonation in English: An Instrumental and Systemic Perspective” has carried out an interesting study on intonation.He points out that a major difficulty of doing description of intonation is the inherently gradient characteristic of the spoken medium. Watt offers a revealing quote from Bolinger: 'The higher the rise, the greater the exasperation if it is a statement, the greater the surprise of curiosity if it is a question. The lower the fall the greater the certainty or finality if the utterance is a statement, and the greater the confidence if it is a question'. That is, in Watt's own words: '...the greater the degree of the rise, or the height of a given contour, the greater the strength of the contextual meaning assumed for that contour'.