1. 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, wherein the statement trigger string determination unit executes the determination based on a higher one of a similarity between the statement and media stream contents at and around the time when the statement is made and a similarity between the statement and language stream contents prior to the time when the statement is made.
4. The topic transition analysis system according to claim 1 comprising: at least one 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.