Provided is a recommendation system comprising: a head-mounted display; and an extraction server for extracting at least one instance of second content on the basis of first content viewed using the head-mounted display. The head-mounted display comprises a sensing part for sensing brain waves of a user while the user is viewing the first content. The extraction server comprises: a sorting part for sorting into categories a plurality of users on the basis of information relating to the brain waves of the plurality of users; and an extraction part for extracting, as the second content, content associated with another user in the same category as a given user and not associated with the given user.
RECOMMENDATION SYSTEM, INFORMATION PROCESSING DEVICE, AND AI SERVER