2. The dialogue speech recognition system according to claim 1 , wherein the linguistic likelihood computation unit includes: a first linguistic likelihood identification unit that identifies a likelihood from a first linguistic model indicating a linguistic likelihood when a speaker having generated a speech signal has the turn to speak; and a second linguistic likelihood identification unit that identifies a likelihood from a second linguistic model indicating a linguistic likelihood when a speaker having generated a speech signal does not have the turn to speak, and the maximum likelihood candidate search unit acquires a candidate for a speech recognition result by using at least one of a linguistic likelihood identified by the first linguistic likelihood identification unit and a linguistic likelihood identified by the second linguistic likelihood identification unit according to the turn information.
4. The dialogue speech recognition system according to claim 2 , wherein the maximum likelihood candidate search unit linearly combines the linguistic likelihood identified by the first linguistic likelihood identification unit and the linguistic likelihood identified by the second linguistic likelihood identification unit according to the turn information, and acquires a candidate for a speech recognition result from the speech signal by using the linearly combined maximum likelihood.