8. A topic transition analysis system comprising: a statement trigger string determination unit receiving a primary media stream and one or a plurality of language communication streams (hereinafter, language streams) executed in parallel with the media stream and determining whether or not a certain statement on the one or plurality of language streams has been made newly in response to contents of the media stream; and one or a plurality of topic similarity calculation unit calculating a topic similarity between the statement and a media stream at and around the time when the statement is made and a topic similarity between the statement and a group of statements made immediately before the statement, wherein the statement trigger string determination unit determines a string having a higher topic similarity to be a string that has triggered the statement.
9. The topic transition analysis system according to claim 8 , wherein at least one of the topic similarity calculation unit receives the statement and one or a plurality of statement groups which are similarity calculation targets, calculates document vectors with respect to the statement and the statement groups by adding weight to each term included in the statement and the statement groups based on a given algorithm, calculating distances among these document vectors, and calculating topic similarities based on the distances.