An information processing device stores, in a keyword database, keywords extracted from speech sounds picked up by a speech-sound processing device as keywords matching keyword entries in a dictionary database of the speech-sound processing device. The information processing device receives, from the speech-sound processing device, an instruction to update the dictionary database of the speech-sound processing device, and then determines, by inference, words related to the keywords stored in the keyword database, prepares an update of the dictionary database on the basis of the keywords stored in the keyword database and the related words determined by inference, and transmits the update of the dictionary database to the speech-sound processing device.