A brain activity training apparatus, comprising: a brain activity detecting device for time-sequentially detecting signals indicative of brain activities at a plurality of prescribed regions in a brain of a first subject; and a storage device for storing information that specifies a discriminator generated from signals measured in advance by time-sequentially measuring signals indicative of the brain activities at said plurality of prescribed regions in a brain of each of a plurality of second subjects different from said first subject, said discriminator executing a discrimination of a target attribute among attributes of said second subjects by contraction expression extracted, from correlations of brain activities in said plurality of prescribed regions, each correlation relating to a different pair of prescribed regions, commonly with respect to at least attributes of said plurality of second subjects; said brain activity training apparatus further comprising: a presenting device; and a processing device; wherein said processing device is configured to i) calculate a correlation of brain activities for each pair of prescribed regions, based on signals detected by said brain activity detecting device, ii) based on said calculated correlations, by said discriminator specified by the information stored in said storage device, calculate a reward value in accordance with degree of similarity of said calculated correlations to target correlations corresponding to said target attribute, and iii) present information indicative of magnitude of said reward value to said subject by said presenting device. a brain activity detecting device for time-sequentially detecting signals indicative of brain activities at a plurality of prescribed regions in a brain of a first subject; and a storage device for storing information that specifies a discriminator generated from signals measured in advance by time-sequentially measuring signals indicative of the brain activities at said plurality of prescribed regions in a brain of each of a plurality of second subjects different from said first subject, said discriminator executing a discrimination of a target attribute among attributes of said second subjects by contraction expression extracted, from correlations of brain activities in said plurality of prescribed regions, each correlation relating to a different pair of prescribed regions, commonly with respect to at least attributes of said plurality of second subjects; said brain activity training apparatus further comprising: a presenting device; and a processing device; wherein said processing device is configured to i) calculate a correlation of brain activities for each pair of prescribed regions, based on signals detected by said brain activity detecting device, ii) based on said calculated correlations, by said discriminator specified by the information stored in said storage device, calculate a reward value in accordance with degree of similarity of said calculated correlations to target correlations corresponding to said target attribute, and iii) present information indicative of magnitude of said reward value to said subject by said presenting device. a presenting device; and a processing device; wherein said processing device is configured to i) calculate a correlation of brain activities for each pair of prescribed regions, based on signals detected by said brain activity detecting device, ii) based on said calculated correlations, by said discriminator specified by the information stored in said storage device, calculate a reward value in accordance with degree of similarity of said calculated correlations to target correlations corresponding to said target attribute, and iii) present information indicative of magnitude of said reward value to said subject by said presenting device. i) calculate a correlation of brain activities for each pair of prescribed regions, based on signals detected by said brain activity detecting device, ii) based on said calculated correlations, by said discriminator specified by the information stored in said storage device, calculate a reward value in accordance with degree of similarity of said calculated correlations to target correlations corresponding to said target attribute, and iii) present information indicative of magnitude of said reward value to said subject by said presenting device.