Abstract: An information processing device includes: an index calculation unit configured to calculate an at least one index of one of actions and reactions by a target on the basis of target information acquired by an information acquisition unit; and a determination unit configured to determine a current psychological status of a plurality of psychological statuses of the target on the basis of the calculated at least one index. After the information acquisition unit acquires the target information, the index calculation unit updates the at least one index on the basis of the acquired target information. After the index calculation unit updates the at least one index, the determination unit determines, on the basis of the updated at least one index, that another one psychological status in a rank that is one of higher and lower than a rank of the current psychological status is a new current-psychological status.