INFORMATION PROCESSING DEVICE, INFORMATION PROCESSING METHOD, INFORMATION PROCESSING DEVICE PROGRAM, AND RECORDING MEDIUM

A pair search word, which is obtained by forming a pair of a preceding search word and a subsequent search word in the search times, is generated in accordance with an order of the search times, from search words in which intervals between the search times associated with the identical user specifying information are within a predetermined time, with reference to a search word memory means which stores the search words. A first appearance count of a pair search word among generated pair search words is calculated, a second appearance count of a reverse order pair search word obtained by reversing an order of a search time of the specific pair search word is calculated, and, when a magnitude relationship between the first appearance count and the second appearance account satisfies predetermined conditions, the preceding search word and the subsequent search word are stored as a thesaurus.